3 international workshop on water in food lausanne,...
TRANSCRIPT
Water Functionality in Food
Water and Food Structure
Water Determination in Food
Water Activity in Food
3rd International Workshop on
Water in Food
Lausanne, Switzerland, March 29-30, 2004
Organised by
EUROPEAN COMMISSION
JOINTRESEARCHCENTRE
ORGANISING COMMITTEE
C.T. Reh (Lausanne, Switzerland) B. Walther (Bern, Switzerland) H.D. Isengard (Hohenheim, Deutschland) K.H. Grobecker (Geel, Belgium) M. Mathlouthi (Reims, France)
SCIENTIFIC COMMITTEE
Water in Food
Water in Food
H.D. Isengard (Hohenheim, Deutschland) E. Anklam (Geel, Belgium) C.T. Reh (Lausanne, Switzerland) K.H. Grobecker (Geel, Belgium) M. Mathlouthi (Reims, France) B. Albrecht (Bern, Switzerland) A. Bernreuther (Geel, Belgium)
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MESSAGE FROM THE LOCAL ORGANISER
Water in Food
Welcome to the 3rd International Workshop « Water in Food » in Lausanne.
The organisers are very proud to present to you an intense program with subjects
ranging from fundamental understanding to industrial applications.
In addition to hearing about the latest scientific and technical developments, you
will have the possibility to meet people with various expertise as well as the
opportunity to connect with old friends and make new ones, nowadays that
bringing d fferent knowledge together has the largest impact on the progress of
science.
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We would like to thank the manufacturers of instruments who wil significantly
contribute to the success of this workshop through the exhibition. The aim here is
to have the chance to be “hands-on” with the ins ruments and perhaps even find
analytical solutions to unsolved problems.
By choosing our workshop venue on the shores of Lake Geneva we hope
everybody will enjoy their time in Lausanne while contributing to progress in food
science and technology.
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EXHIBITION STANDS
Water in Food
Bruker Optik GmbH, Industriestr. 26, 8117 Fällanden, Switzerland CEM, European Sales Office, Amselstr. 6, 75239 Eisingen, Germany Gerber Instruments AG, Im Langhang 12, 8307 Effretikon, Switzerland
Metrohm AG, Oberdorfstr. 68, 9100 Herisau, Switzerland Mettler-Toledo GmbH, Im Langacher, 8606 Greifensee, Switzerland NDC Infrared Engineering, Bates Road, Maldon, Essex CM9 5FA, UK Novasina, Talstr. 35-37, 8808 Pfäffikon, Switzerland Process Sensors Ltd, Corby Gate Business Park, Corby, Northants NN17 5JG, UK Rotronic AG, Grindelstr. 6, 8303 Bassersdorf, Switzerland Sartorius AG, Weender Landstr. 94-108, 37075 Göttingen, Germany Surface Measurement Systems Ltd, 3 Warple Mews, London W3 ORF, UK TEWS Elektronik, Sperberhorst 10, 22459 Hamburg, Germany
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PROGRAMME
Water in Food
Monday 29th March
8:00 Inscription and registration
9:15 – 9:30 Opening
9.30 – 12:30 Session I: Water and Food I 9:30 – 10:00 Water Activity in Aqueous Solutions of Sucrose: an Improved
Temperature Dependence Maciej Starzak1*, Mohamed Mathlouthi2
1School of Chemical Engineering, University of Kwazulu-Natal, Durban, South Africa 2Laboratoire de chimie physique industrielle, Université de Reims Champagne-Ardenne, Reims, France ........................................... 12
10:00 – 10:30 Antiplasticizing Effect of Water in Cereal Products
P.P. Lewicki*, A. Marzec Warsaw Agricultural University, Department of Food Engineering and Process Management, Poland ................................................ 13
10:30 – 11:30 Coffee break and exhibition 11:30 – 12:00 NMR Study of the Water Diffusion in Casein Systems.
Effect of the Micellar Casein Concentration F. Mariette*, A. Métais CEMAGREF, Food Process Engineering Research Unit, France.... 14
12:00 – 12:30 A Mathematical Approach for Modeling the Effects of Moisture Migration and Sustained Delivery of Antimicrobial Compounds in Composite Food V. Guillard1, N. Gontard1, E. Roca1, V. Issoupov1*, S. Guilbert2 1Université Montpellier II, Montpellier, France 2INRA, Montpellier, France............................................................ 15
12:30 – 14:00 Lunch buffet and exhibition
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14:00 – 15:50 Session II: Microwave Spectroscopy 14:00 – 14:30 Microwave Dielectric Spectra and the Composition of Foods:
Multivariate Analysis versus Artificial Neural Networks. Michael Kent*, Frank Daschner, Reinhard Knöchel Lehrstuhl für Hochfrequenztechnik, Christian Albrechts Universität zu Kiel, Germany........................................................................... 18
14:30 – 15:00 Moisture Determination in Food Substances by Means of Millimeter
Waves V.V. Meriakri*, E.E. Chigrai. M.P. Parkhomenko Institute of Radioengineering and Electronics Russian Academy of Sciences, Laborarory of Millimeter Measurements, Russia ........... 19
15:00 – 15:30 About Bound and Free Water Determination by Dielectric Spectroscopy S.V. von Gratowski Institute of Radioengineering and Electronics Russian Academy of Sciences, Russia .......................................................................... 20
15:30 – 15:50 Moisture Measurement with the Microwave Resonance Method E. Pilz*, P. Rath TEWS Elektronik Hamburg, Germany............................................ 21
15:50 – 16:20 Coffee break and exhibition
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16:20 – 18:10 Session III: Near Infrared Spectroscopy 16:20 – 16:50 Successful Installations of On-line NIR Water Gauges in Food
Processes H. Federle FH Furtwangen, Deutschland........................................................ 24
16.50 – 17:20 On-Line Determination of Water in Food Products by NIR
Spectrosensor M. Meurens*, G. Lepoutre Louvain University, Department of Applied Biology, Belgium ........ 25
17:20 – 17:50 Study of Water-Sugar Interactions at Increasing Sugar Concentration by NIR Spectroscopy Roberto Giangiacomo Istituto sperimentale lattiero caseario, Lodi, Italy ......................... 26
17:50 – 18:10 Water Analysis of Food Products with at-line and on-line FT-NIR Spectroscopy Andreas Niemöller Bruker Optik GmbH, NIR & Process Technology, Germany........... 27
18:10 – 20:00 Break and free time (walk in Ouchy) 20:00 Conference dinner
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Tuesday 30th March
8:00 – 12:00 Session IV: Water and Food II 8:00 – 8:30 Dry Coating using AQOAT, a New Method for Encapsulation of Water
Sensitive Products E. Teunou*, E. Ivanova, D. Poncelet National High School of Food Technology, Department of Food Process Engineering, France........................................................ 30
8:30 – 9:00 Acoustic Properties of Crunchy Products P.P. Lewicki1*, A. Marzec1, Z. Ranachowski2 1Warsaw Agricultural University, Department of Food Engineering and Process Management 2Polish Academy of Sciences, Institute of Fundamental Technological Research, Poland................................................... 31
9:00 – 9:30 Analysis of Water binding in Starch Films
M. Mathlouthi1*, B. Rogé1, P. Dole2 1Laboratoire de chimie physique industrielle, UMR FARE, Faculté des Sciences, Reims, France 2Equipe emballage et matériaux d’origine agricole, UMR FARE, Reims, France............................................................................... 32
9:30 – 10:30 Coffee Break and Exhibition 10:30 – 11:00 Variable Hydration of Small Carbohydrates for Prediction of
Equilibrium Properties in Diluted and Concentrated Solutions L. Ben Gaïda, C.G. Dussap, and J.B. Gros* Laboratoire de Génie Chimique et Biochimique, Université B. Pascal, CUST, Aubière, France ................................................................. 33
11:00 – 11:20 Thermodynamic Properties of Water in Amorphous Carbohydrates:
Physical and Chemical Considerations Johanna Claude* and Job Ubbink Nestle Research Center, Switzerland ........................................... 34
11:20 – 11:40 Characterising the Amorphous State in a Pharmaceutical Powder Using Moisture and Organic Vapour Sorption Frank Thielmann1, Dan Burnett1, Juergen Adolphs2* 1Surface Measurement Systems Ltd, London, UK 2Porotec GmbH, Hofheim, Germany .............................................. 35
11:40 – 12:00 Heat of Sorption Measured using a Chilled Mirror Dew Point Water Activity Meter G. S. Campbell*, E. M. Huffaker, and A. J. Fontana Decagon Devices, Inc., USA ......................................................... 36
12:00 – 13:45 Lunch buffet and exhibition
13:45 – 15:35 Session V: Water Determination I
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13:45 – 14:15 Criteria and Tools for a Robust and Reliable Determination of the
Water Content in Dehydrated Foods by Adapted Drying Techniques G. Vuataz Nestle Research Center, Switzerland ........................................... 38
14:15 – 14:35 Influence of Water on the Property Values of Certified Reference Materials S. Yazgan1*, A. Bernreuther1, F. Ulberth1, H.-D. Isengard2 1European Commission, Directorate General Joint Research Centre, Institute for Reference Materials and Measurements, Belgium; 2University of Hohenheim, Institute of Food Technology, Germany....................................................................................... 39
14:35 – 14:55 Proposal of a New Reference Method to Determine the Water Content of Dried Milk Products R. Kling1*, H.-D. Isengard1, C.T. Reh2 1University of Hohenheim, Institute of Food Technology, Germany 2Nestlé Research Center, Switzerland .......................................... 40
14:55 – 15:15 Determination of Water Content in Soluble Coffee by Karl Fischer Method C.T. Reh Nestle Research Center, Switzerland ........................................... 41
15:15 – 15:35 Coulometric Karl Fischer Titration with a Diaphragm-free Cell: Cell Design and Applications M. Lanz*, A. De Agostini, C.A. De Caro, K. Rüegg Mettler-Toledo GmbH, Analytical, Schwerzenbach, Switzerland ... 42
15:35 – 16:15 Coffee break and exhibition
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16:15 – 17:55 Session VI: Water Determination II 16:15 – 16:35 A simple Approach towards Method Uncertainty of Moisture
Methods L. Spack*, C.T. Reh Nestle Research Center, Switzerland ........................................... 44
16:35 – 16:55 Uncertainty Estimation of Gravimetric Water Vapour Permeability Determination of Flat Materials and Finished Objects L. Lundquist*, Y. Wyser, C. Pelletier Nestle Research Center, Switzerland ........................................... 45
16:55 – 17:15 Quantitative Detection of Traces of H2O in Solids H. Nagel Sartorius AG, Moisture Analysis Technology, Germany ................ 46
17:15 – 17:35 Water / Moisture Analysis by Time-Domain Nuclear Magnetic Resonance (TD-NMR) Harald Todt Bruker Optik GmbH, Rheinstetten, Deutschland ........................... 47
17:35 – 17:55 Moisture Measurement in Meat Products by Microwave Drying and Fat Determination by NMR Analysis Steven P. Hailey CEM Corporation, Metthews, USA................................................. 48
18:00 End exhibition and free discussion
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Water in Food
Session I: Water and Food I
Chair: M. Mathlouthi
Session I - Water and Food I
13
.
WATER ACTIVITY IN AQUEOUS SOLUTIONS OF SUCROSE: AN IMPROVED TEMPERATURE DEPENDENCE
Maciej Starzak1*, Mohamed Mathlouthi2
1School of Chemical Engineering, University of Kwazulu-Natal, Durban, South Africa 2Laboratoire de chimie physique industrielle, Université de Reims; Champagne-Ardennes,
France [email protected]
A comprehensive experimental data analysis was performed to quantify the effect of temperature on the water activity coefficient and on related thermodynamic functions for solutions of sucrose in water. An n-suffix Margules equation with temperature-dependent parameters was used to fit various pieces of thermodynamic data involving measurements of saturated vapor pressure, boiling point, osmotic pressure, freezing point, sucrose solubility, heat of dilution and heat capacity. The resulting empirical equation gives an excellent representation of the available literature data on sucrose solutions in a wide range of temperatures (from -15 to 170ºC) and sucrose concentrations (up to 99 % by weight). It can be used as a reliable predictive tool at temperature/concentration conditions not yet explored experimentally, these being of particular interest to the sugar confectionery technologist. Regardless of temperature, the predicted water activity coefficient vs sucrose concentration curves exhibit a characteristic minimum value at extremely high sugar contents. The curves then increase dramatically to values well above 1 as predicted by some theoretical models (Van Hook, 1987; Starzak & Mathlouthi, 2002). The investigated temperature effect on water activity was found to be moderate at low sucrose concentrations, as previously known, but quite substantial for highly concentrated solutions (above 80 % wt. sucrose). Keywords: water activity, sucrose concentrated solutions, temperature effect
Session I - Water and Food I
14
ANTIPLASTICIZING EFFECT OF WATER IN CEREAL PRODUCTS
P.P. Lewicki*, A. Marzec Warsaw Agricultural University, Department of Food Engineering and Process Management, Poland
[email protected] Water activity affects mechanical properties of food, which depend on the chemical composition, microscopic structure and the method of manufacturing of the product. Generally it is observed that increasing water content changes rheological properties of the material from brittle or visco-elastic to plastic. Hence, water is regarded as a plasticizer promoting movement of structural elements one in respect to others under the influence of external force. Published data show that loss of crunchiness occurs at narrow range of water activity or water content in the product. The aim of this work was to investigate the influence of water activity on mechanical properties of crunchy cereal products. Extruded flat bread (wheat, rye and corn-buckwheat), crackers and corn flakes were used as material under investigation. Breaking test and compression were applied to follow deformation of the tested material in respect to applied force. Water activities were in the range from 0.01 to 0.90. It was found that the influence of water activity on mechanical resistance of the material could be treated as its property. The breaking and compression curves of dry material are jagged and the jaggedness decreases with increasing water activity. At some water activity, specific (critical) for a given product, the curves become smooth and plastic flow is observed. At water activities below that value two types of behavior are observed. In some products breaking and compression force increases with increasing water activity. Material becomes harder, and water serves as antiplasticizer. In other products the deformation force is not affected by water activity until values close to critical water activity are reached. At these values substantial increase of force is observed and shortly thereafter a plastic flow occurs. Again, water antiplasticizes the material and increases its resistance to deformation. Keywords: crunchiness, breaking test, compression, extruded flat bread, crackers, corn flakes
Session I - Water and Food I
15
NMR STUDY OF THE WATER DIFFUSION IN CASEIN SYSTEMS EFFECT OF THE MICELLAR CASEIN CONCENTRATION
F. Mariette, A. Métais
CEMAGREF, Food Process Engineering Research Unit, France
[email protected] Models based on different physical concepts such as obstruction effects, free volume concepts and hydrodynamic interactions have been proposed to describe the reduction of the water diffusion in polymer solutions or gels. Several of them require numerous physical parameters relating to the system under study or are based on scaling concepts. Other theories are based on solution of Fick's first law for different geometries. One of this approach using the cell-model was developed by Jönsson et al. (1986). This approach allow the description on the diffusion of small molecule or solvent molecule in heterogeneous system. We evaluated this model to describe the effect of varying concentration of protein on the water diffusion. The protein solution were prepared from micellar casein powder. Different amount of micellar casein were added in a solution of NaCl (0.1M). The water self-diffusion coefficient was measured by Pulsed Field gradient NMR technique at 20°C. All NMR measurements were performed on a 20 MHz Bruker spectrometer, equipped with a field gradient probe. The diffusion experiments were performed using the spin echo sequence. The dependence of the water diffusion coefficient on the casein concentration is reported. The results was then analysed according to the cell-model approach. B.Jönsson, H. Wennerström, P.G. Nilson, and P. Linse, Colloid & Polymer Sci 264:77-88 (1986)
Session I - Water and Food I
16
A MATHEMATICAL APPROACH FOR MODELING THE EFFECTS OF MOISTURE MIGRATION ANDSUSTAINED DELIVERY OF ANTIMICROBIAL COMPOUNDS IN COMPOSITE FOOD
V. Guillard1, N. Gontard1, E. Roca1, V. Issoupov1*, S. Guilbert2
1Université Montpellier II, Montpellier, France 2INRA, Montpellier, France
Water is a constituent of food which affects food safety, stability, quality and physical properties. The influence of water on food properties comes from interactions between water molecules and other constituents of food. Adding an edible layer on the interface, changing the water activity, effective diffusivity of water and viscosity in heterogeneous domains of food are several means to control water migration and diffusion rate (dynamics of mass transfer) in such systems. A model is developed for numerical simulation of the kinetics of moisture migration in two-compartment food represented by a sponge-cake in contact with a fresh wet filling. The derived theory contains both the Fick and the Ferro Fontan equations assuming internal equilibrium of the system. Transport and equilibrium water properties were determined through water sorption isotherm, diffusivity and permeability measurements. The diffusivity and sorption kinetics were then used to predict the diffusion barrier properties and moisture content evolution in two-compartment food with an edible film eventually placed on the interface to prevent moisture transfer. The model was successfully validated using experimental results for a number of bi- and tri-compartment systems. From a practical point of view, the results show that the model provides an accurate and simple prediction of the moisture distribution profiles as a function of time, initial moisture content and water activity. In a particular case, the developed theory was applied to describe the sustained delivery of an antimicrobial agent (sorbic acid) incorporated into or coated onto food packaging materials which leaves a surface layer and diffuses into a model food (agar agar gel) and thus contributes to the food preserved qualities. The predictive ability of the model was tested in migration measurements of sorbic acid from gluten and beeswax films and allowed to characterize its potential activities in suppressing microbial growth and oxidative deterioration. It is shown that the proposed model can be generalized to more realistic food systems like packaged multi-compartment food, taking into account three-dimensional moisture transfer when direct contact between food constituents is not assured and moisture transfer takes place between each of food components, the headspace and the external environment through the packaging material. The developed mathematical theory can be used to facilitate the optimization of the sustained delivery process and to assist the development of related systems. Keywords: water diffusion, mathematical modeling, composite food, preservation
Water in Food
Session II: Microwave Spectroscopy
Chair: K.H. Grobecker
Session II - Microwave Spectroscopy
19
MICROWAVE DIELECTRIC SPECTRA AND THE COMPOSITION OF FOODS: MULTIVARIATE ANALYSIS VERSUS ARTIFICIAL NEURAL NETWORKS
Michael Kent*, Frank Daschner and Reinhard Knöchel
Lehrstuhl für Hochfrequenztechnik, Christian Albrechts Universität zu Kiel, Germany
[email protected] During the last few years several publications have appeared, using the microwave complex dielectric spectra of foodstuffs coupled with multivariate analysis to determine the composition (water, protein etc. added water), and even prior treatment of the food. Most of the published work has extracted compositional information from such spectra by transforming them using multivariate techniques such as principal component analysis and regression (PCA and PCR) and partial least squares regression (PLSR), which have been used in chemometrics for many years. Yet another possibility for data analysis is that using artificial neural networks (ANN). A comparison of all these approaches using dielectric spectroscopy is the subject of this paper. Taking existing dielectric spectra data sets for pork and chicken products with varying compositions, ANN analysis has been applied with some success. The standard errors for prediction of variables, such as water, fat, protein, salt, and added water are improved compared to using PCR or PLSR. The only drawback appears to be the large amount of data required for such calibration. Keywords: microwave dielectric spectroscopy, multivariate analysis, artificial neural networks
Session II - Microwave Spectroscopy
20
MOISTURE DETERMINATION IN FOOD SUBSTANCES BY MEANS OF MILLIMETER WAVES
V.V. Meriakri ∗, E.E. Chigrai. M.P. Parkhomenko Institute of Radioengineering and Electronics, Russian Academy of Sciences, Laborarory
of Millimeter Measurements, Russia
[email protected] Water content may strongly influence on the food product properties. Therefore it is very important to have on-line methods and devices for monitoring water content in food substances. Here we discuss the main peculiarity of application of the relatively new millimeter (MM) wavelength region to such monitoring in comparison with well- known methods based on microwaves as well as on infrared and optical waves [1-3]: 1. MM waves ensure better on-line in real time sensitivity to the water content and better spatial resolution than microwaves (absorption of MM waves in water α > 15 dB/mm is much greater than α in practically all monitored host media; besides as wavelength λ decreases, the absorption in water increases more rapidly than the absorption in these host materials). 2. MM waves are less sensitive than microwaves to conductivity of host substances. 3. MM waves can be used for testing substances that are opaque for optical and infrared waves. We have proved the possibility of water content monitoring in liquid and powder food materials. The devices for such measurements have a certain wave guiding structure connected to a material under test. The measuring parameters (amplitudes and phases of transmission and reflection coefficients of the propagating wave) are changed due to the presence of water in the material under test. We investigated water emulsions in oils. In the MM wavelength range, oils have real part of permittivity ε′ =1.9 -2.2 and imaginary part of permittivity ε′′ = 0.002 -0.005 depending on sort. These values for water are 30 -6. Such difference allows us to have high sensitivity (about 0.03% vol.) to water content W in oils. Next substances of interest are water-alcohol and water-sugar solutions. Table presents
and for water- alcohol solutions depending on alcohol content W, % vol., T = 20°C[3]. ,ε ,,ε
Table
W 0 10 22 40 94,5 96 ε′ 19.6 12.4 8.6 6.4 4.2 4.1 ε′′ 29.0 21.2 14.6 7.9 0.9 0.8
For powders it was found that accuracy of water content determination is about 0.2-0.1%. [1] V.N. Apletalin, B.M. Garin, V.V. Meriakri, «Dielectric properties of liquids in the
submillimeter band», Radio Engineering and Electronic Physics (USSR), 1983, vol. l28, No.1, pp.1-15.
[2] V.V. Meriakri, E.E. Chigrai, I.P. Nikitin, «Monitoring the water content of media and materials with millimeter waves», Radio and Communications Technology (Russia), 1996, vol.1, No 2, pp. 92-96
[3] V.V. Meriakri, E.E. Chigrai, M.P. Parkhomenko, Millimeter waves for water content monitoring in materials and media, 11. Feuchtetag 2002, 18/19.Vortrage, September in Weimar, S. 13-22
Keywords: millimeter, waves, water, measurement
Session II - Microwave Spectroscopy
21
ABOUT BOUND AND FREE WATER DETERMINATION BY DIELECTRIC SPECTROSCOPY
S.V. von Gratowski
Institute of Radioengineering and Electronics Russian Academy of Sciences, Russia
[email protected] The terminal water activity (aw) refers to this unbound water. Water Activity (aw) is a measure of the ‘free’ water in a food sample, as opposed to the ‘bound’ water. Microwave and millimeter wave spectroscopy give possibility for non destructive on-line measurement water content determination with the use investigation real and image parts of dielectric permittivity ε=ε′+iε′′. Free and bound water have quite different dielectric properties, like relaxation time, dielectric permittivity and so on. The higher the binding of water to food matrices, the lower the water activity and lower the relaxation frequency because this prevents water molecule from easily following the alternative electric field. Hence a study of dielectric relaxation spectra, and in particular relaxation frequency, is likely to offer a solution to access water activity [1]. In the last time experimental investigations of free and bound water in food with the use of microwave dielectric spectroscopy was carried out [1-3]. Many food substances can be assumed as admixture of nonpolar matrix with polar dissemination. Water is one of such polar substance. For theoretical investigation of dielectric properties and free and bound water content we calculate the Debye relaxation of dielectric permittivity for a admixture of free water, bound water in nonpolar matrix. Debye relaxation in nonpolar matrix is negligible. For determination of dielectric permittivity of food admixture mean of microscopic polarization of admixture was calculate. The obtained complex permittivity ε depends on full moisture content, dielectric properties of bound water and percent of bound water in full water content.
freebound )1( εα−+αε=ε , ( )
bound,freerel
bound,freebound,free0
bound,freebound,free i1 ωτ+ε−ε
+ε=ωε∞
ω
, α- percent of free, 1-α percent of bound water. The measurement of real and image parts ε on some frequencies of microwave and millimeter wave range give possibility to find out α, or percent of free and bound water. For measurement of free water it is better to investigate in the millimeter wave range, on frequencies near 1/τ rel of free water [4]. In this range there are reliable date for free water [5]. The investigation of bound water must be carried out in microwave range, near 1/τrel of bound water. [1] S. Clerjon, J.-D. Daudin, J.-L.Damez. Water activity and dielectric properties of gels in
the frequency range 200 MHz –6 GHz. Food Chemistry. 2003. [2] F. Henry, S. Houitte, L. C. Costa, M. Serpelloni. Dielectric method for the determination
of aw. 2nd International Workshop on Water in Food. Reims, France [3] F. Henry, M. Gaudillat, L. Cadillon Costa, F. Lakkis. Free and/or bound water by
dielectric measurements 2nd International Workshop on Water in Food. Reims, France.
[4] H.J Liebe, G.A. Hufford, T. Manabe, F model for the complex permittivity of water at frequencies below 1 THz, International Journ. Of Infrared and Millimeter Waves, vol.12, no7, pp. 659-675, 1991
[5] V.V. Meriakri, E.E. Chigrai, M.P. Parkhomenko, Millimeter waves for water content monitoring in materials and media, 11. Feuchtetag 2002, 18/19. Vortrage, September in Weimar, s.13-22.
Keywords: bound water, free water, microwave aquametry
Session II - Microwave Spectroscopy
22
MOISTURE MEASUREMENT WITH THE MICROWAVE RESONANCE METHOD
E. Pilz*, P. Rath
TEWS Elektronik Hamburg, Germany
[email protected] The advantages of the microwave resonance method are the very fast and accurate measurement and the independence of density, colour and surface structure. Hence, the method works non-destructive and includes the determination of the core moisture. Solutions for process control and laboratory are available. The method uses the dipole character of the small water molecules. The microwave resonance field (a standing wave) above or inside a special sensor penetrates the product what contains water. The interaction of the water in the product with the resonance field leads to a shift of the resonance frequency and a increasing of the bandwidth of the peak. The calculation of both parameters generates a moisture value, independent of density and additional a value for the density. The method is a non-direct one and the measuring values have to be calibrated against a direct standard method (e.g. drying oven or Karl-Fischer titrator). The influence of big temperature changes can be compensated. For process control the sensor looks disc-like (planar sensor) and can be integrated in a silo wall, a vibration conveyer or a transmission point of two conveyers to measure the moisture directly. Furthermore a by-pass system with a cylindrical sensor and valves can be used. For the laboratory there are available different sized sensors depending on the accuracy, the amount of product and the moisture range. The applications are spread up in a wide range: Food and natural products, chemistry and pharmacy, tobacco industry, wood and construction material. Keywords: moisture, density, microwave, resonance
Water in Food
Session III: Near Infrared Spectroscopy
Chair: C. Reh
Session III - Near Infrared Spectroscopy
25
SUCCESSFUL INSTALLATIONS OF ON-LINE NIR WATER GAUGES IN FOOD PROCESSES
H. Federle*
Fachhochschule Furtwangen, Department of Product Engineering, Germany
Today NIR technology is the major principle used for on-line water measurement in food. Although this method is well known since many years the user should know what are the main influence parameters to achieve good results. These factors cover the requirements from quality control, production and service; the product itself with shape, particle size and water range and naturally the specifications of the gauge. In a good number of food processes the existing production control of water measurement is still be done by quality staff which means collecting samples from the line and evaluate them by the respective laboratory method. To replace this procedure by an on-line water measurement and most probably integrating the signal in a closed loop control the whole process has to be looked at to get the best return on investment. To select the best available NIR gauge on the market the user should be aware of the main features and their importance on readings of these systems. Parameters like sensitivity to pass height changes, influence of ambient light, reproducibility, accuracy, calibration procedure, measurement range and necessary service have to be considered beside the price of the gauge. The accuracy has to be determined not only on static measurements but mainly on the dynamic behaviour, which is the normal situation for on-line gauges. Unfortunately calibration chasing is still in some minds. Therefore the decision when an instrument has to be recalibrated is of great importance for a successful application. This recalibration will be in most cases a simple trim adjustment or when new product recipes were developed with different ingredients the full calibration procedure could be necessary. The NIR gauge industry developed therefore systems for routine measurements of samples which can also be used for calibrating on-line systems. To gain the full benefits of on-line water measurements a thorough planning is recommended. Keywords: on-line water measurement, NIR, calibration, routine measurement
Session III - Near Infrared Spectroscopy
26
ON-LINE DETERMINATION OF WATER IN FOOD PRODUCTS BY NIR SPECTROSENSOR
M. Meurens*, G. Lepoutre
Louvain University, Department of Applied Biology, Belgium
Near Infra Red (NIR) spectroscopy is a rapid, non-destructive, technique requiring no sample preparation, which can determine the concentration of several chemical species instantaneously and simultaneously. The application of NIR spectroscopy has been investigated for the process and quality control in food industry since twenty years in our laboratory of spectrophotometry. Several intelligent NIR spectrophotometric sensors (spectrosensors) have been assembled and calibrated for the determination of the main constituents (water, glucids, protids, lipids) of food products (cereals, fruits, vegetables, milk, meat, beverages) in more than ten different factories. The design and the performances of these optical sensors are presented in order to explain how they satisfy the needs of the food industry in the operations of sorting the agricultural raw products, monitoring the transformation processes, controlling the quality of the final food products before and after packaging.
For example, to determine water by NIR transmittance measurement across fruits like in sorting of whole apples or across large thickness of industrial products in process control, it is necessary to use a very robust and sensitive spectrometer with a stationary grating and a silicon CCD detector such as the Ocean Optics USB2000 which is presented here above. Keywords: water, food, NIR spectroscopy, optical sensor
Session III - Near Infrared Spectroscopy
27
STUDY OF WATER-SUGAR INTERACTIONS AT INCREASING SUGAR CONCENTRATION BY NIR SPECTROSCOPY
Roberto Giangiacomo
Istituto sperimentale lattiero caseario, Lodi, Italy
[email protected] The study of water structure has fascinated scientists for a long time. Several different analytical techniques have been used to prove ideal models and to try to assess the conformational status of water molecules both in the pure state and in solutions. Near infrared spectroscopy has been extensively used to determine the C-H, N-H, and O-H interactions and the water behaviour at different temperatures and different physical state. Papers by Bonner and Woolsey (1968), Hirschfeld (1985), Iwamoto et al. (1987), and Lin and Brown (1992) show the modifications induced in the NIR water spectrum by the addition of different salts. The purpose of the present work was to investigate, in greater detail, the spectroscopic response in the NIR region of different sugars in aqueous solutions from low up to high concentrations. The possibility of using NIR in studying the interactions water-sugar was also studied. Solutions of glucose, fructose, and sucrose in the range of concentrations 5-65% were measured in transflectance mode by a NIR scanning spectrometer. Data were taken in the full range of wavelengths 1100-2400 nm, but data processing was focused mainly in the region of the water combination band. Data indicate that by increasing sugar concentration the water band becomes more symmetric and there is a shift of the absorption maximum toward longer wavelengths. The region between 1870 and 1996 nm, which represents the changes in the water structure induced by the addition of increasing solute concentrations, was analysed in detail. Spectra were interpreted in terms of “structure-maker” and “structure-breaker” effects of increasing sugar concentration. To validate this interpretation spectra of salts solutions were collected and interpreted. Fructose, glucose, and sucrose at low concentrations behave as structure breaker of the water cluster, while at higher concentrations they act as structure makers. These results could be of some interest when monitoring by NIR processes like freezing, freeze-drying, drying, cryoconcentration, etc. of fruits and vegetables, where the removal or separation of large amounts of water induce the formation of very concentrated sugars solutions.
Session III - Near Infrared Spectroscopy
28
WATER ANALYSIS OF FOOD PRODUCTS WITH AT-LINE AND ON-LINE FT-NIR SPECTROSCOPY
A. Niemöller
Bruker Optik GmbH, NIR & Process Technology, Germany
[email protected] Today NIR spectroscopy is widely established for analysis of food products, on-line as well as at-line and in the laboratory. Various sampling options enable the fast analysis of liquids, solids and emulsions. NIR is an excellent tool for saving costs of wet chemical analysis by reducing time and reagent use. In addition it is offering financial gains due to increases in yield. Two in-line applications using the Bruker Optics FT-NIR spectrometer Matrix-F configured with reflectance probes are described: The moisture and salt analysis in salted butter and the analysis of fat, moisture and protein in whole milk powder. Not only here, but in general the accuracy of NIR applications is extremely depending on the quality of the reference analysis. Especially drying methods for water and moisture analysis can cause higher deviations between lab and NIR results. In addition different sample amounts for NIR and reference analysis are an often not known source of deviations. Those important aspects of method development are discussed. NIR is used for a long time in food industry and a lot of NIR systems based on different technologies (filter, grating and FT) are running for years with well-established and robust calibration methods. The development of such methods is time consuming and expensive because many samples have to be collected and analysed by the reference methods. Especially collecting samples which are covering the expected range of property values may take a long time depending on product variance. Therefore it is of high interest to transfer spectra and methods if NIR systems are replaced by modern and more accurate FT-based systems. This transfer was successfully done several times for different food applications and is shown in detail. Keywords: FT-NIR, fiber optics, method development, calibration transfer
Water in Food
Session IV: Water and Food II
Chair: A. Bernreuther
Session IV - Water and Food II
31
DRY COATING USING AQOAT, A NEW METHOD FOR ENCAPSULATION OF WATER SENSITIVE PRODUCTS
E. Teunou*, E. Ivanova, D. Poncelet
National High School of Food Technology, Department of Food Process Engineering, France
Today, there is a real infatuation in the use of products containing some living cells or some fragile substances in all area: agriculture, chemical, pharmaceutical and food industries because of their beneficial functional properties and effects on the environment and human health. These products are very sensitive to water and are preferentially used or processed as dried substances to favour their stability, their viability and their activity. They are generally encapsulated (capsules) or attached to a support (tablet or coated particles) for these purposes. The problem is that with all traditional aqueous coating processes, these products can be in contact with water and can loose all the above-mentioned characteristics. That is why new encapsulation or coating methods are developed to overcome this problem. During this presentation, principles and a wide range of dry coating techniques, from the use of non aqueous solvent for dispersion of the coating material to the direct application of the dried coating material as powdered form, including hot melt and the use of non aqueous plasticizers. Then, some few illustrations will be show to underline the advantages and the potential of this technique, such as coating of probiotics and integration of minor ingredients in powders to improve their functionality. The results will show various advantages of dried coating compared to the classical aqueous coating systems, such as high coating yield and energy save in addition to the non-wetting of the product. The results will also reveal some disadvantages, which clearly indicate that these new systems still require some improvements. Keywords: dry coating, wetting, water sensitive products, probiotics
Session IV - Water and Food II
32
ACOUSTIC PROPERTIES OF CRUNCHY PRODUCTS
P.P. Lewicki1*, A. Marzec1, Z. Ranachowski2
1Warsaw Agricultural University, Food Engineering and Process Management, Poland 2Polish Academy of Sciences, Institute of Fundamental Technological Research, Poland
Breaking of brittle materials is accompanied by acoustic emission. Generated sound is typical for crunchy, crisp foods and is an important quality attribute. Quite often it is recognized as a sign of freshness and good manufacturing practice. However, acoustic emission generated by crunchy products during consumption was not a subject of thorough investigations. The aim of this work was to investigate acoustic emission generated during breaking of crunchy products. Extruded flat bread (wheat, rye, corn-rice, corn-buckwheat), biscuits, sponge-cake, crackers, corn flakes and potato chips were used in this experiment. An acoustic accelerometric sensor was mounted near the lower end of the breaking head to achieve an acoustic contact with the fracturing sample. The acoustic signal was amplified and registered in the frequency range 0.1-15 kHz. A 44.1 kHz sampling sound card was used to register acoustic emission. It was found that each product is characterized by a specific acoustic spectrum. Frequency profile could be treated as a property of the product. All investigated products showed two frequency ranges with a high power level of acoustic emission signal. One range occurs at low frequencies and the other one at high frequencies. For example extruded wheat flat bread emitted strong acoustic signals at frequencies 1-3 kHz and 11-15 kHz, while extruded corn-rice flat bread emitted signals at 2-6 kHz and 13-15 kHz. Corn flakes emit acoustic signals at frequencies 6-9 kHz and 13-14 kHz, while crackers give signals at 2-3 kHz and 14 kHz. It was observed that the ranges of characteristic frequencies are not dependent on water content or water activity. However, the signal intensity is strongly related to water activity. Results of this work show that frequency spectrum is a property of the material and is not dependent on water content or water activity. Keywords: acoustic emission, frequency spectrum, water activity
Session IV - Water and Food II
33
ANALYSIS OF WATER BINDING IN STARCH FILMS
M. Mathlouthi1, B. Rogé1, P. Dole2
1Laboratoire de chimie physique industrielle, UMR FARE, Faculté des Sciences, Reims, France
2Equipe Emballage et Matériaux d’Origine Agricole, UMR FARE, Reims, France
[email protected] The water binding properties of wheat starch films were studied through the determination of water vapour adsorption isotherms at 20°C. Starch films were obtained by casting after mixing native starch at 95°C for 15 minutes with plasticizers having different hydrophobicities (glycerol, diethylene glycol, diethylene glycol monomethyl ether). Likewise, water vapour sorption isotherms were established for modified starch films. The modified starches were derivatised using increased hydrophobicity substituents (acetyl, ethyl, butyl and hexamethyl di-isocyanate). Unplasticized starch film was found to adsorb less water than native starch granules. The effect of glycerol on water vapour adsorption by plasticized films depends on water activity (aw) value and glycerol content. Below aw = 0.44, plasticized film is less hygroscopic than native starch and above this value, adsorbed water increases with glycerol content. An amount of 20% glycerol seems to be the maximum that can act as plasticizer. Above this percentage, an increased rate of adsorbed water binds to “free glycerol”. Starch plasticized by diethylene glycol (2 OHs as compared to 3 OHs in glycerol) shows a behaviour comparable to that of glycerol, with a lower level of effective plasticizer maximum (12 – 13%) and less adsorbed water. With diethylene glycol monomethyl ether (1OH), plasticized starch film adsorbs less water than unplasticised film. The percentage of plasticizer does not seem to affect adsorption of water. The degree of substitution (D.S.) affects the adsorption of water by the films made with substituted starches. Increasing the D.S. leads to a decrease in water adsorption. Likewise an increased length of substituent chain increases hydrophobicity and induces a diminution of adsorbed water. Determination of monolayer water using B.E.T. equation allows confirmation of the role of hydrophobicity on water vapour adsorption by modified starch films. Moreover, a D.S. = 1 seems to be a limit above which a constant monolayer (3g water/100g film) is adsorbed. The hydration of plasticized starch films depends on the nature and amount of plasticizer. Water vapour adsorption is proportional to the number of hydrophilic sites (OHs) in the plasticizer. Modified starch films adsorb less water than native or plasticized films. The higher the hydrophobicity of substituent, the lower the amount of adsorbed water. Binding of water to starch films influences their thermo-mechanical properties. Keywords: starch film, plasticizer, water vapour adsorption, modified starch
Session IV - Water and Food II
34
t
VARIABLE HYDRATION OF SMALL CARBOHYDRATES FOR PREDICTION OF EQUILIBRIUM PROPERTIES IN DILUTED AND CONCENTRATED SOLUTIONS
L. Ben Gaïda, C.G. Dussap, and J.B. Gros*
Laboratoire de génie chimique e biochimique, Université B. Pascal, CUST, Aubière, France
Water is the main component in most foods and equilibrium properties of water are considered as reference properties in food processing. Water activity is an example. A physical chemical model is proposed to describe equilibrium properties of binary and multicomponent water-carbohydrate mixtures. The chemical part of the model accounts for the hydration equilibrium of carbohydrate with the formation of carbohydrate nh-water molecules in a single stage process; nh called the maximum hydration number and Kh the hydration equilibrium constant, are the two independent parameters in this part. The physical part of the model is the UNIFAC group-contribution model as modified by Larsen et al. (I.E.C. Research, 26, 2274-2286,1987). The original functional groups and the structural and interaction parameter values are maintained and introducing new groups such as pyranose rings, furanose rings and osidic bonds is not necessary. The maximum hydration number is obtained considering a constant maximum hydration of the hydroxyl functional group in the UNIFAC Larsen model. The hydration equilibrium constant is the only remaining adjustable parameter. The model is compared to experimental data including water activity, osmotic coefficients, activity coefficients, freezing and boiling point temperatures, for systems containing xylose, glucose, mannose, galactose, fructose, sucrose, maltose, lactose and trehalose.
Session IV - Water and Food II
35
THERMODYNAMIC PROPERTIES OF WATER IN AMORPHOUS CARBOHYDRATES: PHYSICAL AND CHEMICAL CONSIDERATIONS
Johanna Claude*, Job Ubbink
Nestlé Research Center, Lausanne, Switzerland
[email protected] Water is a key element in amorphous carbohydrates because of its strong interactions with carbohydrates which lead, in particular, to a strong plasticization. How these interactions arise on a molecular level and their influence on important properties like the diffusion of small molecules like gases or flavor compounds in such matrices remain largely open questions, however. We address these issues by combining thermodynamic analyses with a study of the barrier properties of amorphous carbohydrates. Two examples of our recent research on physical and chemical aspects of carbohydrate thermodynamics will be presented:
1. The sorption of water in dense maltodextrin matrices is studied in the glassy state. Water is adsorbed in these carbohydrate glasses with a partial molar volume, which is around 9 ml/mole, i.e. considerably lower than in the liquid state. This implies a strong interaction between the absorbed water and the carbohydrate matrix, as is also shown using a Zimm-Lundberg clustering analysis of the water sorption isotherms. We discuss the implications for matrix stability and swelling in the glassy state.
2. The early stages of the thermal decomposition of maltodextrin are studied as
function of the molecular weight and the water content using colorimetry. Maltodextrin samples equilibrated at 25°C at various water activities are subjected to elevated temperatures for various intervals using specially constructed, hermetically sealed cells. Color formation of the maltodextrin samples is followed colorimetrically and an Arrhenius model is developed to quantify the degree of thermal decomposition. The data show that to a good approximation the color formation can be modeled using activation energy, which is independent of the physical state of the matrix (rubbery or glassy). The relevance of the results for carbohydrate processing and storage is highlighted.
Session IV - Water and Food II
36
CHARACTERIZING THE AMORPHOUS STATE IN A PHARMACEUTICAL POWDER USING MOISTURE AND ORGANIC VAPOUR SORPTION
Frank Thielmann1, Dan Burnett1, Juergen Adolphs2*
1Surface Measurement Systems Ltd., London, UK 2Porotec GmbH, Hofheim, Germany
Amorphous materials in food formulations yield complex and challenging problems concerning the performance, processing, and storage of these products. For these reasons, fully characterizing the amorphous state is crucial. Dynamic gravimetric vapour sorption (DVS) is a well-established method for the determination of water and organic vapour sorption isotherms. It is based on a highly sensitive gravimetric system, which measures the adsorption and desorption of extremely small amounts of probe molecule. In the current studies water sorption experiments were performed to determine the glass transition as well as the exact onset relative humidity that will cause amorphous sugars to recrystallize. These experiments were combined with in-situ video microscopy to correlate features in the moisture sorption profile with visible changes in the sample. Amorphous lactose was chosen as a model sugar and exposed to a linearly ramped humidity profile from 0% to 90% RH. At a critical RH, the amorphous lactose passes through the glass transition due to the plasticizing effect of water. As amorphous lactose passes through the glass transition, it recrystallizes to form lactose monohydrate, as indicated by the sharp change in vapour sorption capacity. This was performed for a series of ramping rates. A clear relationship exists between the onset glass transition RH and the RH ramping rate, allowing extrapolation to a ramping rate of zero, or the sample’s inherent glass transition RH. For this lactose sample at 25.0 C, the inherent glass transition RH was 29.8% and the recrystallization onset at 58%RH. Moisture sorption experiments coupled with in-situ video microscopy collected in-situ during the ramping experiments support the physical changes indicated by the moisture sorption profile. Keywords: amorphous materials, glass transition, moisture sorption
Session IV - Water and Food II
37
HEAT OF SORPTION MEASURED USING A CHILLED MIRROR DEW POINT WATER ACTIVITY METER
G. S. Campbell*, E. M. Huffaker, and A. J. Fontana
Decagon Devices, Inc., Pullman, WA USA
[email protected] The water activity of foods changes with temperature. Typically, increasing temperature increases water activity, but decreasing water activity with increasing temperature has also been observed. The magnitude of the temperature effect typically decreases as the sample water activity increases, and becomes negligible at very high water activity. If the matrix binding the water is stable with temperature, the effect of temperature on water activity can be predicted using
lnaa
QR T T
s2
1 1
1 1= −
2 where a1 and a2 are water activities at Kelvin temperatures T1 and T2, R is the gas constant (8.3143 J mol-1 K-1) and Qs is the heat of sorption (J/mol). In general, the value of Qs depends on the makeup and the water activity of the sample. If Qs is known, then one can predict the temperature dependence of the water activity. As the name implies, Qs is also a measure of how tightly water is bound by the sample. A plot of ln a vs. 1/T should produce a straight line with slope Qs/R. Multiplying the slope by R gives the heat of sorption. We measured heats of adsorption for corn, wheat flour, mustard seed, and powdered milk using an Aqualab Series 3TE with internal temperature control. Sample temperatures ranged from 16 to 40 C, and water activities from 0.1 to 0.75. Heats of sorption ranged from near zero to about 16 kJ/mol. In corn, wheat flour and powdered milk Qs decreased rapidly with increasing water activity. In mustard seed Qs was near zero and changed little with water activity. In addition to providing measurements from which Qs can be computed, these experiments give the temperature dependence of water activity which is useful for storage studies.
Water in Food
Session V: Water Determination I
Chair: H.D. Isengard
Session V - Water Determination I
39
CRITERIA AND TOOLS FOR A ROBUST AND RELIABLE DETERMINATION OF THE WATER CONTENT IN DEHYDRATED FOODS BY ADAPTED DRYING TECHNIQUES
G. Vuataz
Nestle Research Center, Switzerland
[email protected] Determining the true water content (all the water content but only water) in dehydrated foods remains a challenge for food scientists. A reliable true method should minimise outside chemical formation of any volatiles during drying. An adapted drying condition first requires understanding the mechanisms of water desorption and diffusion through the food matrix. To achieve this a correct description of the food material structure is necessary. Physical techniques such as sorption under controlled conditions, thermal analysis and near infrared reflectance analysis have been found very powerful for practical applications. Some criteria will be discussed, mainly based on the state diagram and water physics: • How to select the optimal drying temperature profile? • How to guarantee a final fully dry state at the end of the drying? • What would affect the diffusion of the water molecules through a glassy matrix? Practical examples for selected food materials such as dairy or non-dairy powders and green coffee beans will be presented using specific tools: • Sorption equipment for characterising the water mobility through glassy matrices • Simultaneous Thermo-Gravimetry and Differential Thermal Analysis for evaluating
the binding state of water • Near Infrared Reflectance for detecting residual water content after drying Thanks to such tools and advances in food physics, the methods currently applied in the food industry may be revised and improved for establishing new reliable references methods necessary for food quality and safety, as well as food processing. Moreover, this physical approach of food science will help in understanding the role of residual water on the rate of reactions that often occur above the glass transition in the glassy state.
Session V - Water Determination I
40
INFLUENCE OF WATER ON THE PROPERTY VALUES OF CERTIFIED REFERENCE MATERIALS
S. Yazgan1*, A. Bernreuther1, F. Ulberth1, H.D. Isengard2
1European Commission, Directorate General Joint Research Centre, Institute for Reference Materials and Measurements, Belgium
2University of Hohenheim, Institute of Food Technology, Germany
[email protected] Property values of powdered certified reference materials (CRMs) are very often related to dry mass. The dry mass is indirectly determined by measuring the water/moisture content of the sample. Different methods for water/moisture content determination exist. The most commonly used methods are the drying oven method and the Karl Fischer titration. It is well known that these two methods may give different values for the water/moisture content. Taking the Karl Fischer titration (KFT) as a reference method the drying parameters (temperature, time etc.) should be determined and proposed to the user of the reference materials. Thermogravimetric analysis is an appropriate tool to simulate the drying process and to elaborate correct parameters for water/moisture content determination. A mass spectrometer coupled to the thermobalance (TG-MS) adds further useful information regarding the release of volatile substances during the drying process. The relative humidity of the laboratory may influence the water content of powder CRMs because of their more or less pronounced tendency to take up water. This fact can lead to biased property values. The hygroscopicity (adsorption kinetics) and the water uptake capacity vary, depending on the constitution of the sample. Water uptake kinetics give additional valuable information on a material. In this study, three methods (KFT, drying oven, TG-MS) for water/moisture content determination in several powdered CRMs were compared and the adsorption behaviour was investigated. CRMs and individual constituents of powdered food CRMs, such as pectin, starch or gelatine, have served as examples. Pectin showed a fast uptake of water. Within ten minutes it adsorbed approximately 7 % water. The water uptake of casein was approximately 2 % within 10 min. Further technical and experimental details and the corresponding results will be discussed in this presentation. Keywords: certified reference materials, water content, moisture content, Karl Fischer
titration, drying oven, sorption isotherms, adsorption kinetics
Session V - Water Determination I
41
PROPOSAL OF A NEW REFERENCE METHOD TO DETERMINE THE WATER CONTENT OF DRIED MILK PRODUCTS
R. Kling1*, H.D. Isengard1, C.T. Reh2
1University of Hohenheim, Institute of Food Technology, Germany 2Nestlé Research Center, Switzerland
The moisture content of dried milk products is determined according to ISO/FDIS 5537/IDF 26:2003 (E): 5 g are dried for 5 hours in an air-stream (33 ml/min) at 87 °C. The results depend strongly on these parameters. Water occurs in different fractions in milk powders: as crystallised water of �-lactose, as water bound to proteins and as free water. Water can also be produced during the heating process by thermal decomposition reactions. A particular problem with milk products is the lactose content. In the α-modification it contains one mole water per mole. A major part of this crystallised water is not detected by the new IDF method mentioned above. The results do therefore not represent the true water content. The Karl Fischer titration, however, detects this water fraction. It is based on a chemical reaction selective for water. The standard technique was changed for this application: The titrations were carried out with formamide as additional solvent and at a temperature of about 50 °C. This method was tested on several types of dried milk products. The titration curves indicate a complete water detection. The precision and also the accuracy of the results are better. The difference between the mass loss by drying and the water content determined by Karl Fischer titration increases with the lactose content. The table shows this for two different milk powder products:
Sample (10 replicates each for every method)
Water content by Karl Fischer titration [g/100g]
Mass loss by drying [g/100g]
Milk powder 4.57 ± 0.028 (sr = 0.61 %) 4.22 ± 0.096 (sr = 2.28 %) Whey powder 4.58 ± 0,039 (sr = 0.85%) 1.97 ± 0.180 (sr = 9.14 %)
The difference between the drying results and the true water content analysed by titration is not acceptable. The titration has the advantage to detect all the water of this sort of products, while the result of the drying technique is not really defined. It is therefore proposed to establish the Karl Fischer method as reference method for water content determination in dried milk products. Keywords: milk powders, water content, Karl Fischer titration, drying oven, reference method
Session V - Water Determination I
42
DETERMINATION OF WATER CONTENT IN SOLUBLE COFFEE BY KARL FISCHER METHOD
C. T. Reh
Nestle Research Center, Switzerland
[email protected] The determination of the water content in foodstuff is one of the most frequently performed analyses in the food industry. In soluble coffee powder ISO method 3726-1983 the sample is dried at 70.0°C ± 2.0°C in an oven under reduced pressure (50 mbar) for 16 hours. The method exhibits excellent repeatability but reproducibility is often insufficient. Therefore the ISO working group has prepared the proposal of ISO TC 34/SC 15 which is based on the principle of the Karl Fischer method. With the Karl Fischer method it is possible to measure the total water content in soluble coffee powder as long as all water molecules present in whatever form in the product are dissolved in the solvent. In this study we measured the moisture or water content of a large number of soluble coffee powders by several techniques (drying by vacuum oven, desiccation by P2O5, drying by standard oven (95°C for 2 hours), Karl Fischer) and used water activity and near infrared spectroscopy to further understanding. We show how the measurement techniques relate to each other and demonstrate that the Karl Fischer technique seems to be the most precise and best-defined method. This results, when the Karl Fischer method is applied properly, in the best reproducibility of the tested methods. Keywords: soluble coffee, moisture content, Karl Fischer, water content
Session V - Water Determination I
43
COULOMETRIC KARL FISCHER TITRATION WITH A DIAPHRAGM-FREE CELL: CELL DESIGN AND APPLICATIONS
M. Lanz*, A. De Agostini, C.A. De Caro, K. Rüegg
Mettler-Toledo GmbH, Analytical, Schwerzenbach, Switzerland
[email protected], [email protected] Coulometric Karl Fischer titration is a useful technique for wide-range water determination, from a percentage level down to trace amounts at the ppm level. For trace water determinations, a coulometric Karl Fischer titration cell having a current generator with a diaphragm, separating the anodic and the cathodic compartment, has proven to be useful. From an applicative point of view, a diaphragm-free cell for Karl Fischer coulometry is favourable because of its ease-of-use. Such a cell is easier to refill and to clean than a cell having a diaphragm. Further, there are no problems such as contamination and clogging of the diaphragm, or unwanted standby drift values due to impurities or moisture leaking out of the diaphragm. Therefore, optimisation of the diaphragm-free coulometric KF titration in such a way that it can be used down to the trace water determination level would be an advantage to the users. With a Karl Fischer titration cell having a non-optimised, diaphragm-free current generator, trace water determinations may yield too high values due to a partial chemical and electrochemical reduction of the anodically generated iodine. Chemical reduction of anodically generated iodine may occur through oxidizable reduction products, which are produced at the cathode when the cathodic current density is too low. They can be avoided through larger generating currents. Direct electrochemical reduction of the anodically generated iodine at the cathode can be diminished by optimising the geometry of the Karl Fischer cell. Thus, optimisation of the diaphragm-free Karl Fischer titration involves both optimising the cell geometry and optimising the electrochemical control of the titration, i.e., the current generation at the iodine-generating anode and its cathodic counter-electrode. We show in this presentation that under optimum conditions, trace water amounts down to less than 10–20 µg of water can reliably be determined with such a commercially available, optimised diaphragm-free Karl Fischer equipment. In particular, applications on water determination in foods are presented. Keywords: Karl Fischer titration, coulometry, diaphragm-free cell
Water in Food
Session VI: Water Determination II
Chair: J. Prodolliet
Session VI - Water Determination II
45
A SIMPLE APPROACH TOWARDS MEASUREMENT UNCERTAINTY OF TESTS METHODS FOR MOISTURE CONTENT
L. Spack*, C. T. Reh
Nestle Research Center, Lausanne, Switzerland
[email protected] One of the requirement of the new ISO Norm 17025 regarding accredited test laboratories concerns the measurement uncertainty of results. The application to chemistry of the ISO Guide to the expression of uncertainty of measurement was issued by EURACHEM in 1995. In consequence control laboratories require calculating measurement uncertainty for the accreditation of the performed techniques. In this presentation we will explain our approach to measurement uncertainty estimation, giving the example of the methods determining the moisture and water content. The examples include standard oven drying of powders (moisture) and liquids (dry matter) and the water content by the Karl Fischer method. The procedure used for the estimation of measurement uncertainty follows the recommendations given in the Eurachem Guide. Therefore, it is divided into six steps:
1. Description of the method 2. Specification of the measurand 3. Identification of all uncertainty sources 4. Quantification of individual uncertainty components 5. Calculation of combined uncertainty 6. Expression of final expanded uncertainty
At the end of the presentation we will put the method uncertainty data in the perspective of results we collected in collaborative studies on a number of products. This comparison allows illustrating the validity of the approach. Based on the available data we are now in a good position to optimise methods and to fix limits of acceptability. The good use of food samples as reference materials is part of this approach. Keywords: measurement uncertainty, oven, water content, moisture, Karl Fischer, food, dry matter
Session VI - Water Determination II
46
UNCERTAINTY ESTIMATION OF GRAVIMETRIC WATER VAPOUR PERMEABILITY DETERMINATION OF FLAT MATERIALS AND FINISHED OBJECTS
L. Lundquist*, Y. Wyser, C. Pelletier
Nestlé Research Center, Switzerland
[email protected] Gravimetric determination of water vapour permeability (WVTR) of packaging has found widespread use within Nestlé. The method is extremely simple, requiring only a climatic chamber with controlled temperature and humidity and a precision balance. The measurement uncertainty related to this method has, to the knowledge of the authors, never been evaluated. Knowledge of the uncertainty related to the method is, however, a prerequisite in order to determine the minimum allowable package permeability required to ensure the product shelf life. In this work the measurement uncertainty related to three different methods of gravimetric WVTR measurements are evaluated: weigh change, weigh change with correction for buoyancy effects using an inert reference volume, and weight change with correction for air buoyancy and material water absorption using a blank sample. Films and finished objects of varying levels of permeability are investigated. For low permeability films the relative expanded measurement uncertainty may reach levels as high as 140% when using a blank, whereas for high permeability films it remains in the vicinity of 10%. The measurement uncertainty on finished objects is considerably lower due to a larger surface of penetration and larger weight changes per unit time. Extending the testing period and increase of the time span between measurements reduces uncertainty. Keywords: water vapour permeability, gravimetry, packaging, measurement uncertainty
Session VI - Water Determination II
47
QUANTITATIVE DETECTION OF TRACES OF H2O IN SOLIDS
H. Nagel*
Sartorius AG, Department of Product Management, Moisture Analysis Technology, Germany
Coulometric Karl Fischer titration is the internationally recognized standard method for determining water content in solids. Similarly, the phosphorus pentoxide method works according to the proven principle of coulometry. Technically, analysis by the WDS 400 – Water Detection System - is comparable to coulometric Karl Fischer titration, but is limited to just a few steps. A known amount of the sample compound (25 – 2,000 mg) is placed in a scoop, transferred to the WDS 400’s built-in oven and heated according to a defined temperature curve. This enables the various bonding forms of water to be differentiated into surface water, capillary water or the more tightly bound water of crystallization. This method harnesses the different physical forces, such as van der Waals forces, hydrogen bonds, dipolar or even interactive electrostatic forces that cause water to bind to compounds in the sample. The water vapor produced is transferred to the electrolytic sensor using N2 as the carrier gas (Fig. 1). The sensor consists of a ceramic disk that is coated with a thin layer of phosphorus pentoxide. This layer is located between two electrodes arranged in parallel. As the water vapor-charged gas passes over the phosphorus pentoxide, a chemical reaction takes place that causes electrolytic dissociation of the water molecule. The charge required for complete dissociation during electrolysis is quantitatively measured. Then, Faraday's law is applied to convert the charge measured into the amount of water contained in the initial sample tested. Its catalytic properties allow the sensor to self-regenerate during a measurement in progress.
Figure 1: Analytical setup (schematic) Analysis by WDS 400 includes a quantitative evaluation of the different bonding forms of water, indicated in ppm/% and µg of water. The detection limit of this method is around 1 µg of water and covers a measuring range of approx. 20% water content. Keywords: phosphorus pentoxide method, WDS 400, trace water, quantitative evaluation
Session VI - Water Determination II
48
WATER / MOISTURE ANALYSIS BY TIME-DOMAIN NUCLEAR MAGNETIC RESONANCE
G. Guthausen, H. Todt
Bruker Optik GmbH, Minispec Department, Germany Time-Domain Nuclear Magnetic Resonance (TD-NMR) is widely used within Food Industries for QC/QA applications, but also for R&D purposes. The analysis are mainly based on relaxation time and diffusion experiments. The NMR properties such as relaxation times of water molecules are strongly dependent on the neighbouring surrounding / environment. Whereas crystal water exhibits relaxation times in the order of some tens of microseconds, bound water has an intermediate relaxation behaviour, the NMR signal decays within a few hundreds of microseconds. Free water may show NMR signal up to seconds. Therefore TD-NMR is suitable for a qualitative and quantitative examination of food samples with respect to water binding. Having these properties in mind, total signal amplitudes can be used to determine moisture / water in a quantitative way. As food samples usually contain also fat / lipids exhibiting relaxation times of a few hundred milliseconds, the minispec methods have to differentiate all these components, using typically the relaxation properties as contrast parameter. The minispec applications analysing bound water – here called moisture - are well-known for many years and have become International standard methods. Typically samples like oilseeds, milk powders, bakery powders and chocolate etc are examined in respect to moisture and lipids content. Samples with high water content or free water can be also addressed with the recently introduced Bruker TURBOLIPID solution package. This comprehensive analysis considers the different customer requirements and offers an optimum solution for almost each problem. Besides the analysis on packaged products, the mq-Relaxation Time Analysis should be mentioned here. This pure one step NMR analysis requires only filling of the sample into an adequate sample tube and subsequent introduction into the minispec system. It was shown that the 3 parameters water, fat and protein can be measured simultaneously within few minutes. The non-homogenous nature of samples like meat is considered, too, by analysing an adequate amount of several 10g. TD-NMR can also visualise the diffusion properties of the water molecules by pulsed field gradient methods. A typical example is the determination of droplet size distributions of w/o and o/w emulsions, providing information about sample properties like life time, emulsion stability, taste and spread behaviour.
Figure: Bruker minispec TD-NMR Analyser Keywords: TD-NMR, water relaxation, crystal water, bound water, free water, diffusion
experiments
Session VI - Water Determination II
49
MOISTURE MEASUREMENT IN MEAT PRODUCTS BY MICROWAVE DRYING AND FAT DETERMINATION BY NMR ANALYSIS
Steven P. Hailey
CEM Corporation, Matthews, USA
The purpose of this presentation is to discuss results from the AOAC method PVM1: 2003, microwave drying for percent moisture and NMR analysis for percent fat determinations. Five meat products were analysed by both the submitting and peer laboratories using moisture and fat systems by CEM Corporation. The procedure involves determining the moisture value of meat samples by microwave drying and using the dried sample to determine fat value by NMR analysis. Analysis was performed on samples of: (1) fresh ground beef, high fat; (2) deboned chicken with skins; (3) fresh pork, low fat; (4) all beef hot dogs. These samples were chosen to represent the range of products meat processors must deal with in a normal daily operation. A fifth (5th) sample of NIST standard reference material sample was also analysed. Moisture and fat values form AOAC reference methods 950.46 Forced Air Oven Drying and 960.39 Soxhlet Ether Extraction were use for comparison purposes. Keywords: microwave oven, moisture, meat, rapid method, reference method
Water in Food
Poster Session
Poster session
51
,
MODELING OF WATER VAPOR SORPTION ISOTHERMS AND CAPILLARY CONDENSATION
J. Adolphs
POROTEC GmbH, Hofheim/Ts. Germany
[email protected] An extended version of the computation model for sorption isotherms and capillary condensation from Churaev, Starke and Adolphs [1, 2] is introduced. This model combines a new function the excess surface work Φ and the disjoining pressure approach. A significant basis for both models was the interaction and sorption of water vapor, meanwhile the validity of these sorption models is more general. The excess surface work is defined as the sum of Surface Free Energy and Isothermal Isobaric Work of Sorption and is easily computed as Φ=Γ∗∆µ, with the adsorbed amount Γ and change in chemical potential ∆µ=RT*ln(p/p0). One solution is the Zwicker-deBoer linear plot of ln |∆µ| and Γ. In this contribution it is applied for various pore size distributions of mesopores. The idea is that during adsorption on the porewalls the approaching films will reach a metastable situation and collapse - capillary condensation proceeds. Evaporation is described with a modified Kelvin equation. Particularly for cylindrical pores is found much evidence that the surface tension is dependent on the pore size. Successfully computations of experimental data of sorption with water as well as nitrogen and argon on various nanoporous materials emphasize this dependency. Besides the entire computation of sorption isotherms with hysteresis (or no hysteresis in case of very small pores) it is also possible to determine with nonpolar sorptives the monolayer Γmono and specific surface area with the ESW model [3-5]. Keywords: water vapor sorption, modeling, excess surface work, disjoining pressure
p/ p s Γ mono
Γ Φ=Γ∆µ
Γ
ln |∆µ|
Γ
-1/ Γ mono
0 1
Fig. 1 Scheme of the transition of an isotherm into an ESW plot and linearization
1. Churaev, N.V., Starke, G., Adolphs, J., J. Colloid Interface Sci. 221, 246 (2000). 2. Churaev, N.V., Adolphs, J., Colloid J + 62: (4), 495 (2000). 3. Adolphs, J., Setzer, M. J., J.Colloid Interface Sci., Vol. 180., 70 (1996). 4. Adolphs, J., Setzer, M. J, J. Colloid Interface Sci., Vol.184. 443 (1996). 5. Adolphs, J.:” Modeling of Gas Adsorption at Porous and Dispersed Surfaces”, in
Surface and Interface Sciences (ed. Arthur Hubbard), 3472-3482 (2002).
Poster session
52
INFLUENCE OF HONEY TYPE AND STATE OF CRYSTALLISATION ON THE WATER ACTIVITY OF HONEY
R.A. Gleiter 1,2*, H. Horn2, H.-D. Isengard1
1University of Hohenheim, Institute of Food Technology, Germany 2Institute of Bee Keeping, Germany
380 samples of different honey types were analysed for water content and water activity. The samples were identified using physico-chemical parameters and melissopalynological methods. The moisture content was determined via refractometric measurement at 20 °C. Crystallised honeys were liquefied in an incubator without loss of water. The water activity of liquefied and crystallised honeys was measured at 25 °C using the instrument Novasina aw-Sprint. It was found that the water activities of crystallised honeys are higher than those of liquid honeys. Furthermore a difference between flower and honeydew honeys could be detected. In the liquid state honeydew honeys show higher water activities than flower honeys having the same moisture content. No difference between the water activities of different honeys was found when the honey was crystallised. The findings can be explained by the fact that water activity in honey mainly depends on the glucose content. Glucose crystallises before fructose. Fructose has a higher solubility and stays in solution for a longer time during the crystallisation process. Glucose has five hydroxyl groups and fixes some molecules of water via hydrogen bonds. After crystallisation glucose is found as glucose monohydrate. Therefore less water is bound in the crystallised state. The content of free water is higher and in accordance with the water activity. Honey types have different glucose/fructose-ratios. In general, flower honeys contain more glucose than honeydew honeys. Flower honeys can therefore fix more water. This applies only for the liquefied samples. In crystallised honeys glucose fixes less water. Consequently, the glucose/fructose-ratio is of no relevance. Keywords: honeys, water activity, water content, state of crystallisation, glucose/fructose ratio
Poster session
53
NMR ASSESSMENT OF WATER TRANSPORT IN BREAKFAST CEREALS: A QUANTITATIVE APPROACH
T. Lucas *, D. Le Ray and F. Mariette
CEMAGREF , Food Process Engineering Research Unit, France.
[email protected] Although low- and intermediate moisture content foods are increasingly incorporated in ready-to-eat meals elaborated at the industrial scale, the rehydration operation is still empirically conducted and surprisingly has been the object of very few studies. Recent works carried out on milk powders rehydrated in different aqueous media showed the interest of the NMR technique for better understanding the mechanisms underlying the rehydration process. The present work aims at exploring these potentialities of the NMR technique, with particular focus on the feasibility of multi-scale studies, from granules (several µm) to food pieces (several mm). Time-course changes in NMR signal during rice crispies immersed in water were assessed and a quantitative demarche was developed to attribute the different NMR components to the different water compartments and to convert the NMR signal into water absorption kinetics. Keywords: rehydration, water absorption, solute leaching, continuous non-invasive measurement
Poster session
54
FOURIER TRANSFORM INFRARED SPECTROSCOPY AS A PROBE FOR THE STUDY OF THE HYDRATION OF SUCROSE, CAFFEINE AND THEIR MIXTURES IN WATER
B. Rogé1, V. Aroulmoji1, M. Mejri2, M. Mathlouthi1*
1*Laboratoire de Chimie physique industrielle, UMR 614 FARE, Faculté des Sciences, Université de Reims, Champagne Ardenne, France
2Laboratoire de Génie Biologique de l’INSAT, Université de Tunis Carthage, Tunis, Tunisie
[email protected] Physico-chemical properties of sweet and bitter substances and that of their mixtures in aqueous solvent are vital to elucidate the mechanism of taste chemoreception. These properties may also be used as a predictive tool for the formulation of foods and pharmaceuticals. At the origin of the physico-chemical properties are chemical structures of sweet and bitter molecules and their interactions with water. Depending on the polarity and concentration of solute, its hydration and effect on solvent (water) structure may affect the perception of taste. Recently, we have studied the physico-chemical and surface properties of sucrose, caffeine and their mixtures in aqueous solution. The viscometric constants and apparent specific volume show a noticeable effect of sweet molecules on the hydration properties of the bitter substance caffeine. Although sucrose is known to slightly enhance the surface tension (γ) of water, the values of γ for mixtures are lower than that of pure water. This is interpreted as an enhancement of adsorption of bitter molecules on hydrophobic receptor membrane. In order to understand more about the role of water mobility in taste perception, we studied sucrose (sweet), caffeine (bitter) with various concentrations and their mixtures in water by FT-IR spectroscopy The observed IR spectra of pure caffeine with increasing concentrations (0.005 M to 0.1 M) show spectral changes in the carbonyl-stretching region. This was interpreted in terms of the self-association equilibria resulting from the staking of caffeine molecules. This study was also repeated with increasing sucrose and fixed caffeine concentration to understand the influence of sucrose on caffeine solution. In addition, a deconvolution method of the experimental IR envelope (3000-3500 cm-1) of sucrose, caffeine and its mixtures were studied in order to understand the perturbation of water components by the solute. As water mobility was an important aspect in interpreting sweet taste chemoreception, IR spectroscopy study of water help in understanding the role of water structure in taste modalities.
Water in Food
Authors index
Authors index
A
AA
Adolphs J., 35, 50 Aroulmoji V., 53
BB
Ben Gaïda L., 33 Bernreuther A., 39 Burnett D., 35
CC
Campbell G.S., 36 Chigrai E.E., 19 Claude J., 34
DD
Daschner F., 18 De Agostini A., 42 De Caro C.A., 42 Dole P., 32 Dussap C.G., 33
FF
Federle H., 24 Fontana A.J., 36
GG
Giangiacomo R., 26 Gleiter R.A., 51 Gontard N., 15 von Gratowski S.V., 20 Gros J.B., 33 Guilbert S., 15 Guillard V., 15 Guthausen G., 47
HH
Hailey S.P., 48 Horn H., 51 Huffaker E.M., 36
II
Isengard H.D., 39, 40, 51 Issoupov V., 15 Ivanova E., 30
KK
Kent M., 18 Kling R., 40 Knöchel R., 18
LL
Lanz M., 42 Lewicki P.P., 13, 31 Lepoutre G., 25 Le Ray D., 52 Lucas T., 52 Lundquist L., 45
MM
Mariette F., 14, 52 Marzec A., 13, 31 Mathlouthi M., 12, 32, 53 Mejri M., 53 Meriakri V.V., 19 Métais A., 14 Meurens M., 25
NN
Nagel H., 46 Niemöller A., 27
PP
Parkhomenko M.P., 19 Pelletier C., 45 Pilz E., 21 Poncelet D., 30
RR
Ranachowski Z., 31 Rath P., 21 Reh C.T., 40, 41, 44 Roca E., 15 Rogé B., 32, 53 Rüegg K., 42
SS
Spack L., 44 Starzak M., 12
TT
Teunou E., 30 Thielmann F., 35 Todt H., 47
UU
Ubbink J., 34 Ulberth F., 39
VV
Vuataz G., 38
WW
Wyser Y., 45
YY
Yazgan S., 39
57
Water in Food
List of participants
List of participants BELGIUM BERNREUTHER Alexander CONNEELY Patrick GROBECKER Karl Heinz YAZGAN Seyhan IRMM, Retiesweg 111, 2440 Geel MEURENS Marc University of Louvain, AGRO/BNUT, Croix du Sud, 2(8),
1348 Louvain-la-Neuve DENMARK KOLD-CHRISTENSEN Steen Foss Analytical A/S, 69, Slangerupgade, PO box 260,
3400 Hillerod FRANCE GROS Jean-Bernard University Blaise Pascal, 24, av. des Landais, 63174 Aubière HURET Vincent Dickey-john Europe, 165, bd de Valmy, 92700 Colombes ISSOUPOV Vitali University of Montpellier II, Agropolymer Engineering and
Emerging Technologies, UMR 1208 CC 023, Pl. Eugène Bataillon, 34095 Montpellier Cedex 5
MARIETTE François Cemagref, 17, av. de Cucillé, 35044 Rennes MATHLOUTHI Mohamed University of Reims, Faculty of Science, BP 1039, 51687
Reims Cedex 2 ROCA Elisabeth Agropolymer Engineering and Emerging Technologies, UMR
1208, CC 023, Place Eugène Bataillon, 34095 Montpellier Cedex 5
TEUNOU Ernest ENITIAA, Food Process Engineering Dept, rue de la
Géraudière, PO Box 82225, 44322 Nantes Cedex 3 GERMANY ADOLPHS Jürgen Porotec GmbH, Niederhofheimerstr. 55A, 65719 Hofheim/Ts FEDERLE Hartmut FH Furtwangen, Am Felsen 1, 78147 Vöhrenbach FELGNER Andrea GLEITER Ruth University of Hohenheim, Flandernstr. 103, 73732 Esslingen GRUNEWALD Horst Perten Instruments GmbH, Grossmoorkehre 3, 21079
Hamburg GUTHAUSEN Gisela Bruker Optik GmbH, Silberstreifen, 76287 Rheinstetten ISENGARD Heinz-Dieter University of Hohenheim, Flandernstr. 103, 73732 Esslingen JACOB Ludovic Bruker Optik GmbH, Rudolf-Plankstr. 27, 76275 Ettlingen
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List of participants
KLING Renate University of Hohenheim, Flandernstr. 103, 73732 Esslingen KNÖCHEL Reinhard University of Kiel, Kaiserstr. 2, 24143 Kiel NAGEL Horst Sartorius AG, Weender Landstr. 94 - 108,37075 Göttingen NIEMÖLLER Andreas Bruker Optik GmbH, Rudolf-Plankstr. 27, 76275 Ettlingen PILZ Edgar RATH Paul TEWS Ekektronik, Sperberhorst 10, 22459 Hamburg RABE Swen ROYER Delphine Nestlé Product Technology Center, Lange Strasse 21,
78224 Singen SCHÖNER Axel CEM, European Sales Office, Amselstr. 6, 75239 Eisingen TODT Harald Bruker Optik GmbH, Silberstreifen, 76287 Rheinstetten ICELAND JOHNSSON Olafur Intelscan ehf, Impra, Keldnaholt, 112 Reykjavik
ITALY GIANGIACOMO Roberto Istituto Sperimentale Lattiero Caseario, via A. Lombardo 11,
26900 Lodi THE NETHERLANDS DE KNEGT R.J. COKZ, PO Box 250, 3830 AG Leusden VAN NIEUWENHUIJZEN Neleke Bornsesteeg 59, PO Box 17, 6700 AA Wageningen
POLAND LEWICKI Piotr Warsaw Agricultural University, Dept of Food Engineering
and Process, Ul. Nowoursynowska 159c, 02-776 Warsaw RUSSIA VON GRATOWSKY Svetlana MERIAKRI V.V. Institute of Radio Engineering and Electronics, Russian
Academy of Sciences, Vvedenski sq.1, Fryazino, 141190 Moscow Region
60
List of participants
SOUTH AFRICA STARZAK Maciej University of Kwazulu-Natal, School of Chemical
Engineering, 4041 Durban SWITZERLAND ALBRECHT Bruno Swiss Federal Research Station for Animal Production and
Dairy Products, Schwarzenburgstr. 161, 3003 Bern ALONSO Maria-Isabelle Nestlé Research Center, PO Box 44, 1000 Lausanne 26 BERRUT Stéphane Nestlé Research Center, PO Box 44, 1000 Lausanne 26 BOGONI Carlo Buhler AG, Gupfenstrasse, 9240 Uzwil BOSCHUNG Catherine Nestlé Nespresso SA, rte du Lac 3, 1094 Paudex BRAUN Marcel Nestlé Product Technology Center, Postfach 12, 3510
Konolfingen BÜHLER Hans Gerber Instruments AG, Im Langhang 12, 8307 Effretikon CLAUDE Johanna Nestlé Research Center, PO Box 44, 1000 Lausanne 26 COSTE-SARGUET Annie Nestlé Product Technology Center, 1350 Orbe DE AGOSTINI Antonio DE CARO Cosimo Mettler-Toledo GmbH, Sonnenbergstr. 74, 8603
Schwerzenbach EYER Christoph Panatec AG, Spittelstr. 18, 8712 Stäfa FÄH Urban Bruker Optik GmbH, Industriestr. 26, 8117 Fällanden FIAUX Martine GERBER Ariane Nestlé Research Center, PO Box 44, 1000 Lausanne 26 GUIGNARD Isabelle Nestlé Suisse SA, Regional Laboratory, 1350 Orbe GUMY Jean-Claude Nestlé Product Technology Center, 1350 Orbe HURNI Jürg Novasina, Talstr. 35-37, 8808 Pfäffikon LABAT Emilie Nestlé Research Center, PO Box 44, 1000 Lausanne 26 LANZ Martin Mettler-Toledo GmbH, Sonnenbergstr. 74, 8603
Schwerzenbach LUESCHER Michael Nestlé Suisse SA, Blumenfeldstr. 15, 9400 Rorschach LUNDQUIST Lars Nestlé Research Center, PO Box 44, 1000 Lausanne 26 MASSARO Alfonso Sartorius AG, Lerzenstr. 10, PO Box 672, 8953 Dietikon MEUNIER Vincent Nestlé Research Center, PO Box 44, 1000 Lausanne 26
61
List of participants
I
MÜLLER Markus Dr. Marino Müller AG, Vollikerstr. 22, 8133 Esslingen MÜLLER Peter Rotronic AG, Grindelstr. 6, 8303 Bassersdorf PÈ Giulio Mettler-Toledo GmbH, Im Langacher, 8606 Greifensee PETITP ERRE Bertrand Rotronic AG, Grindelstr. 6, 8303 Bassersdorf POURZAND Farzaneh PRODOLLIET Jacques Nestlé Research Center, PO Box 44, 1000 Lausanne 26 REH Christoph Nestlé Research Center, PO Box 44, 1000 Lausanne 26 REINWALD Norbert Nestlé Nespresso SA, rte du Lac 3, 1094 Paudex ROYER Delphine Nestlé Product Technology Center, Lange Strasse 21,
78224 Singen RÜEGG Katharina SCHAD Roger Mettler-Toledo GmbH, Sonnenbergstr. 74, 8603
Schwerzenbach SCHLINK Regina Metrohm AG, Oberdorfstr. 68, 9100 Herisau
SCHWEIZER Remo Gerber Instruments AG, Im Langhang 12, 8307 Effretikon SPACK Lionel Nestec SA, PO Box 44, Vers-chez-les-Blanc, 1000
Lausanne 26 STUDER Marianne Nestlé Research Center, PO Box 44, 1000 Lausanne 26 STURZENEGGER Kathrin Metrohm AG, Oberdorfstr. 68, 9100 Herisau TCHOUNKEU Ferdinand Nestlé Suisse SA, rue Jules Bellet 7, 1636 Broc VUATAZ Gilles Nestlé Research Center, PO Box 44, 1000 Lausanne 26
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List of participants
63
UK BENSON Jan NDC Infrared Engineering, Bates Road, Maldon, Essex CM9
5FA BOULIOU Violaine Nestlé Product Technology Center, Haxby Road, York Y091
1XY CAREY Tim Process Sensors Ltd, Corby Gate Business Park, Adelaide
House, Corby, Northants NN17 5JG FARHAT Imad A. University of Nottingham, Division of Food Sciences,
Sutton Bonington Campus, Loughborough, LE12 5RD IZZARD Martin Unilever, Bedford MK44 1LQ
KENT Mike University of Kiel, The Whitehouse, Greystone, Carmyllie,
Angus, Scotland DD11 2RJ LITTELWOOD Malcolm NDC Infrared Engineering, Bates Road, Maldon, Essex CM9
5FA SMITH Elaine Nestlé Product Technology Center, Haxby Road, York Y091
1XY THORNTON David Surface Measurement Systems Ltd, 3 Warple Mews,
London W3 ORF USA CAMPBELL Gaylon S. Decagon Devices Inc., 950 NE Nelson Court, Pullman,
Washington 99163 HAILEY Steven P. CEM Corporation, PO Box 9, Matthews, North Carolina