physical quality and in vitro starch digestibility of bread as affected by addition of extracted...

lable at ScienceDirect

LWT - Food Science and Technology xxx (2014) 1e9

Contents lists avai

LWT - Food Science and Technology

journal homepage: www.elsevier .com/locate/ lwt

Physical quality and in vitro starch digestibility of bread as affected byaddition of extracted malva nut gum

Anchalee Srichamroen*

Department of Agro-Industry, Faculty of Agriculture, Natural Resources and Environment, Naresuan University, Phitsanulok Province 65000, Thailand

a r t i c l e i n f o

Article history:Received 28 June 2012Received in revised form14 April 2014Accepted 24 April 2014Available online xxx

Keywords:Malva nut gumBreadDigestibilityDialysisScanning electron microscopy

* Tel.: þ66 55 962746; fax: þ66 55 962703.E-mail address: [email protected].

http://dx.doi.org/10.1016/j.lwt.2014.04.0460023-6438/� 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Srichamromalva nut gum, LWT - Food Science and Tech

a b s t r a c t

Malva nut gum (MNG) was extracted by alkaline solution. The previous studies showed that the extracthad viscosity and gelling properties as well as inhibited a-amylase activity in starch solution 1.5e2.0folds higher than that of original malva nut gum. This research was aimed to investigate the a-amylaseinhibitory effect of alkaline-extracted MNG in solid food and to determine physical properties of MNG-containing bread. The scanning electron microscopy of in vitro digestibility with a-amylase of MNG-containing breads showed less porosity and more undigested starch granules remained intact withthe matrix compared to control. This finding was consistent with the reduction of glucose (33e40%) andmaltose (23e39%) levels compared to that of control after a-amylase digestion for 180 min in a dialysissystem. The results showed that extracted MNG significantly (p < 0.05) increased loaf volume, andmoisture content by 1.5e12%, and 8.2e12.8%, respectively compared to that of control. Addition ofextracted MNG in bread formulation significantly reduced moisture loss and firmness of the bread crumbafter storage for three days.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Increased postprandial plasma glucose during 2 h after meal oftype 2 diabetic subjects (T2D) is associated with the incidence ofcardiovascular disease (Ceriello, 2005; Heine & Dekker, 2002). Aclinical goal of treating diabetic subjects is to decrease postprandialhyperglycemia and cardiovascular risk factors. Diets play a role inpreventing the rapid rise of plasma glucose levels in the post-prandial state. Viscous fibers have been well-known to reducepostprandial blood glucose concentrations in humans and animals(Anderson, Akanji, & Randles, 2001). It was proposed that the fullyhydrated chains of soluble fibers diminish the contact betweenglucose molecules and small intestinal mucosal cells thereforereduce the rate of digestion and absorption of carbohydrate(Blackburn, Redfern, & Jarjis, 1984; Rainbird, Low, & Zebrowska,1984; Torsdottir, Alpsten, Anderson, & Einansson, 1989).

Addition of hydrocolloid to enhance functional properties ofbread has been investigated by increasing number of researchers(Woolnough, Monro, Brennan, & Bird, 2008). These authors re-ported a lower rate of in vitro starch digestibility of bread

en, A., Physical quality and innology (2014), http://dx.doi.o

containing galactomannan compared to wheat bread without gal-actomannan (Brennan, Blake, Ellis, & Schofield, 1996; Slaughter,Ellis, Jackson, & Butterworth, 2002). Other studies used guar gum,locust bean gum, and xanthan gum reported increasing the weightof baked products, improving dough development (Rosell, Rojas, &Benedito, 2001), increasing gas retention of dough, improvingtexture of crumb and crust by controlling moisture retention(Huttner & Arendt, 2010). However, these results are not consistentin some studies. Addition of b-glucan in bread formulationcontributed to a reduced loaf volume and increased crumb firmnesscompared to control wheat bread (Gaosong & Vasanthan, 2000;Gill, Vasanthan, Ooraikul, & Rossnagel, 2002; Symons & Brennan,2004). Addition of hydroxypropylmethylcellulose, a hydrocolloidthat forms thermoreversible gel networks in baked products,increased crumb firmness when added at levels higher than 1.5 kg/100 kg starcheflour blend basis (Sabanis & Tzia, 2011).

Malva nut fruit (Scaphium scaphigerum (G. Don) Guib. et Planch)is native to the South East Asia and China. In Thailand, people haveused the mucilaginous substance of the seeds as traditional medi-cine for laxative benefits. My laboratory has succeeded in produc-ing dietary fibers extracted from malva nut seeds. The extractcontains total dietary fiber 80 g/100 g, protein 2 g/100 g, ash 7 g/100 g (Srichamroen & Chavasit, 2011a). Malva nut gum (MNG)extracted with alkaline solution had carboxylic bonds with the

vitro starch digestibility of bread as affected by addition of extractedrg/10.1016/j.lwt.2014.04.046

Delta:1_given name

mailto:[email protected]

www.sciencedirect.com/science/journal/00236438

http://www.elsevier.com/locate/lwt

http://dx.doi.org/10.1016/j.lwt.2014.04.046



A. Srichamroen / LWT - Food Science and Technology xxx (2014) 1e92

reduction of galacturonic acid contents. This is correlated with theincreased storage moduli (G0) of alkaline-extracted gum with thevalue being higher than that of water-extracted MNG. The previousstudy also showed the a-amylase inhibitory effect of alkaline-extracted MNG in starch solution (Srichamroen & Chavasit,2011b). The alkaline-extracted MNG is new to scientific report. Itis interesting to investigate the ability of MNG to inhibit a-amylaseactivity in solid matrix and to determine the effect of extractedMNG on physical properties of bread.

2. Materials and methods

2.1. Materials

Malva nut seeds harvested during March and April in 2010 wereobtained from local markets in the East of Thailand. Malva nut gumwas extracted in the laboratory at Naresuan University(Srichamroen & Chavasit, 2011a). Briefly, the seeds were ground(0.5 mm mesh size) and dispersed in distilled water at a ratio of1:100 (w/v) and placed in a boiling water bath for 1.5 h. The slurrywas then cooled to room temperature, and added with NaOH to afinal concentration of 0.05, 0.1, or 0.2 mol/L, then treated with ab-solute ethanol at a ratio of 1:1 (v/v). Precipitate was removed torecover MNG. The gum was adjusted to pH 7.4 and dried in hot airoven at 60 �C. All of extracted MNGs were ground to pass through a100 mm sieve before use.

All chemicals, pepsin and a-amylase used in this study were ofanalytical grade and purchased from Sigma Chemical Co. (St. LouisMO, USA). Dialysis membrane (molecular weight cutoff of 12,000)was obtained from Membrane Filtration Products Inc. (SeguinTexas, USA).

2.2. Bread preparation

Wheat bread, called control bread, consisted of 60 g wheat flour,1.5 g dried yeast, 3.5 g soybean oil, 0.5 g salt, 0.5 g sugar, and 34 gwater. Because of high water binding capacity of extracted MNG(Srichamroen & Chavasit, 2011a), water level of MNG-containingbread formulation had to be adjusted in order to avoid underde-veloped gluten network due to increased dietary fiber content.Previous research showed that MNG-containing bread should havean additional 6 g of water when MNG was used 1.7 g/100 g flour.Extracted MNG was boiled to fully hydrate and cooled to roomtemperature prior to be added into the mixture of bread formula-tion. Dough was fermented at 40 �C and 90% relative humidity for2 h in the chamber of incubator (ShelLab model TC2323, CorneliusOR, USA), after which they were kneaded and divided into 210 gportions and put in a bakery stainless steel tin (19 cm length, 8 cmwidth, 8 cm height). Breads were baked in an air oven (Kluay NamThai Trading Group Co., Ltd., Bangkok, Thailand) at 170 �C for20 min. After baking, breads were cooled at room temperature for1 h before analyses. For the study of effect of storage on physicalproperties of bread, bread loaf was kept in a polypropylene bag at4 �C to prevent mold. After certain time of storage (on days 1, 2 and3) bread loaf in a food-grade polypropylene bag (Goldenpack Co.,Chonburi, Thailand) was transferred to room temperature beforefurther analyses. The reason to choose three days of storage was toimitate the use of bread in a local hospital store for diabeticpatients.

2.3. Loaf volume and specific volume

Loaf volume was determined by rapeseed displacement ac-cording to AACC approved Method 10-05 (AACC, 2000). Loaf heightwas determined using calibrated calipers whichmeasured from the

Please cite this article in press as: Srichamroen, A., Physical quality and inmalva nut gum, LWT - Food Science and Technology (2014), http://dx.doi.o

center of the loaf. Specific volume was calculated by dividing loafvolume by weight.

2.4. Moisture content and water activity

Moisture content of bread crumb was determined by heatingsamples in an oven at 105 �C for 12 h. Three bread slices were cutfrom the central loaf and a crumbwas taken from the centre of eachslice and torn into small pieces for moisture determination. Wateractivity of bread crumb was measured at 25 �C using a NovasinaAWC200 water activity meter (Axair AG, Pfäffikon, Switzerland).

2.5. Crumb firmness

The crumb firmness measurement was performed with a QTSBrookfield Texture Analyser (Middleboro, MA, USA). Three breadslices were cut from the central loaf. The central part of each slicewas cut into cubes (2� 2� 2 cm) and subjected to one compressiontest. The sample was compressed to 40% original height at acompression load of 25 kg with a cross-head speed for 60 mm/min.

2.6. Scanning electron microscopy (SEM)

Bread crumb was cut into fine pieces with a blade in order tocreate a clean fracture surface to observe in the scanning electronmicroscope (LEO model 1455 VP, LEO Electron Microscopy Ltd.,Cambridge, England). Sample was mounted on an aluminumsample holder (12 mm diameter) with double sided conductivecarbon tape and a line of carbon paint was painted around the baseof the sample to improve conductivity from the top of the seed tothe taped surface. The sample was then sputter coated with gold(Sputter Coater Model SC 7620, Quorum Technologies Ltd., UK) andplaced in the SEM chamber for examination and photographedusing a 10 kV of electron beam-accelerating voltage.

2.7. In vitro digestibility of starch of the breads

To simulate the hydrolysis reaction in human stomach, pepsin(5.75 units/g starch, Sigma Chemical Co., St. Louis MO, USA) wasadded into 1 mol/L sodium phosphate buffer solution (pH 6.9)which contained fine pieces of bread equivalent to 40 g of wheatflour (Symons & Brennan, 2004). The mixture was adjusted to pH1.5 (with HCl) at 37 �C for 30min. The pH of mixturewas readjustedto pH 6.9 (with NaOH) prior to addition of porcine pancreatic a-amylase (110 units/g starch, Sigma Chemical Co., St. Louis MO, USA).The mixture was transferred to a dialysis bag against 250 mL ofdeionized water in erlenmeyer flask, and stirred at 37 �C in a waterbath shaker. Dialysate (2mL of deionizedwater in erlenmeyer flask)was collected after 15, 30, 60, 120, and 180 min in order to deter-mine glucose and maltose contents.

2.8. Sugar determination

Glucose andmaltose contents in the dialysateweremeasured byusing HPLC system (Shimadzu, Kyoto, Japan). The dialysate (2 mL)was filtered through a 0.45 mm filter and a portion (10 mL) of filtratewas injected into the HPLC column (Inertsil� NH2 5 mm, dimension4.6 � 250 mm). The mobile phase was CH3CN/H2O:75/25 at flowrate 1.0 mL/min, and 40 �C. The HPLC was performed using arefractive index detector with detection limit of 0.01 mmol/L.

2.9. Statistical analysis

All experiments were performed in three replications. Resultswere presented as the mean � SE. Statistical analysis was


A. Srichamroen / LWT - Food Science and Technology xxx (2014) 1e9 3

performed by using SPSS version 15.0 for window. Repeated Mea-surement ANOVA was used for sequenced periodical studies, fol-lowed by StudenteNewmaneKeuls (SNK) test as a post-hocanalysis to detect any significant differences among the groups. A p-value < 0.05 was considered statistical significance. For intervalperiodical study, one way ANOVA was used followed by SNK at p-value < 0.05.

Fig. 1. Slices of control and MNG-containing breads. (A) control bread; (B) bread containingextracted with 0.05 mol/L NaOH; (D) bread containing 0.5 g/100 g MNG extracted with 0.1bread containing 0.5 g/100 g MNG extracted with 0.2 mol/L NaOH; (G) bread containing 1


3. Results

3.1. General appearance

MNG-containing breads showed qualitatively large and smallopen crumb cells more than that of control (Fig. 1). Bread con-taining 0.5 g/100 gMNG showedmixtures of big and small gas cells.

0.5 g/100 g MNG extracted with 0.05 mol/L NaOH; (C) bread containing 1 g/100 g MNGmol/L NaOH; (E) bread containing 1 g/100 g MNG extracted with 0.1 mol/L NaOH; (F)g/100 g MNG extracted with 0.2 mol/L NaOH.


Table 1Physical properties of control and MNG-containing breads.

Bread Height (cm) Loaf volume(mL)

Specific volume(mL/g)

Control 7.73 � 0.03a 700 � 2.90g 3.80 � 0.06b

MNG extracted with 0.05 mol/L NaOH0.5 g/100 g concentration 6.53 � 0.08d 770 � 1.15b 4.20 � 0.06a

1.0 g/100 g concentration 7.03 � 0.14c 742 � 1.53d 4.13 � 0.03a

MNG extracted with 0.1 mol/L NaOH0.5 g/100 g concentration 6.60 � 0.02d 720 � 2.89e 3.60 � 0.06c

1.0 g/100 g concentration 7.40 � 0.05b 710 � 1.73f 3.56 � 0.09c

MNG extracted with 0.2 mol/L NaOH0.5 g/100 g concentration 6.76 � 0.06d 785 � 2.89a 4.20 � 0.01a

1.0 g/100 g concentration 7.06 � 0.03c 750 � 2.77c 4.16 � 0.03a

Data present as mean � S.E. of three independent replicates.aeg different letters following means within the same column indicate a significantdifference at the p < 0.05 level.


While 1 g/100 g MNG containing bread showed big gas cells withfewer amounts of small gas cells.

MNG-containing breads had significantly lower height than didcontrol (Table 1). Addition of 0.5 g/100 g MNG in bread formulationdecreased the height of baked bread by 12e15% of control. Whilethe reduction in bread height was 4e9% with the addition of 1 g/100 g MNGs in bread formulation.

3.2. Loaf volume and specific volume

Addition of 0.5 g/100 g alkaline-extracted MNGs in breadformulation increased loaf volume by 3e12% of control, whileincorporation of 1 g/100 g MNG in the bread resulted in 1.5e7%increase in loaf volume compared to the control (Table 1). MNG-containing breads had significantly higher specific volumecompared to that of control, except for bread containing MNGsextracted with 0.1 mol/L NaOH which had the lowest loaf volumeamong MNG-containing breads (Table 1). Specific volume involvesboth loaf weight and loaf volume. Weights of MNG-containingbreads were not much different, thus loaf volume was a factoraffecting on specific volume. The low specific volume of 0.1 mol/LNaOH extracted MNG-containing bread might be explained by thedifferent peak of spectral FT-IR pattern at 898 and 823 cm�1 (CeHand CeC bond, respectively) whichwas intensely found in 0.1mol/LNaOH extracted MNG (Srichamroen & Chavasit, 2011a). I couldspeculate that MNG extracted with 0.1 mol/L NaOH had high waterholding capacity which led to slightly disturb expansion of glutennetwork and reduced loaf volume.

Table 2Moisture contents of control and MNG-containing breads during three day storage.

Bread Moisture content (g/100 g)

Day 0 Da

Control 40.44 � 0.86b 37MNG extracted with 0.05 mol/L NaOH0.5 g/100 g concentration 43.78 � 0.41a 421.0 g/100 g concentration 45.61 � 0.31a 42

MNG extracted with 0.1 mol/L NaOH0.5 g/100 g concentration 43.98 � 0.56a 411.0 g/100 g concentration 45.47 � 0.29a 42

MNG extracted with 0.2 mol/L NaOH0.5 g/100 g concentration 41.81 � 0.42b 411.0 g/100 g concentration 44.39 � 0.31a 42

Data present as mean � S.E. of three independent replicates.aee different letters following means within the same column indicate a significant diffe


3.3. Moisture content and water activity of baked breads

Addition of extracted MNGs in bread formulation significantlyincreased moisture content by 8.2e12.8% of control bread, exceptfor bread containing 0.5 g/100 g MNG extracted with 0.2 mol/LNaOH which increased moisture content by 3.4% of control(Table 2).

After 24 h of storage at 4 �C, the moisture content of controlbread was lost by 6%, whereas moisture content of MNG-containingbreads was lost by 1.6e6.0% (Table 2). The moisture content ofcontrol bread on day 2 was 9.4% lower than that of day 0. While themoisture content of all MNG-containing breads on day 2 rangedbetween 3.0 and 7.3% lower than that of day 0. After 3 days ofstorage, the control had significantly lowest moisture contentcompared to MNG-containing breads.

The water activity of control bread at day 0 was 0.946, whileMNG-containing breads hadwater activity level ranging from 0.950to 0.964 (data not shown). After 3 days of storage, the water activityof control was 0.937. Water activity values of MNG-containingbreads did not significantly change from day 0 of each formula-tion. These results were in agreement with that of breads con-taining other hydrocolloids which had little change of wateractivity between fresh and older crumb (Abu-Ghoush et al., 2008;Czuchajowska, Pomeranz, & Jeffers, 1989).

3.4. Crumb firmness

Fresh MNG-containing bread significantly increased crumbfirmness by 13e16% of control (Fig. 2). Although fresh MNG-containing bread had higher firmness than that of control, theincreased rate of firmness after storage of MNG-containing breadwas much lower than that of control. The low rate of increasedfirmness of MNG-containing breads was associated with decreasedloss of moisture content.

After 24 h of storage at 4 �C, the firmness of control bread wasincreased by three folds, while the firmness of MNG-containingbreads was increased by 1.05e1.5 folds (Fig. 2). The firmness ofcontrol bread on day 2 and day 3 of storage was much increasedmore than that of MNG-containing breads. The slope coefficient ofincreased firmness of control bread was 8.2 (r ¼ 0.92). While thefirmness of all MNG-containing breads on day 2 and day 3 ofstorage was gradually increased with slope coefficient ranged be-tween 2.2 and 3.2 for 0.5 g/100 g MNG-containing breads and 2.7e3.9 for 1 g/100 g MNG-containing MNG breads (r ¼ 0.85e0.95). Atday one and beyond all MNG-containing breads had softer crumbthan did control bread. Specifically, crumb firmness of control was1.6e2.1 folds higher than that of MNG-containing breads.

y 1 Day 2 Day 3

.86 � 0.18e 36.62 � 0.31c 36.43 � 0.22c

.00 � 0.17bc 42.48 � 0.27a 41.93 � 0.23a

.96 � 0.08a 42.27 � 0.14a 42.16 � 0.16a

.50 � 0.28cd 41.25 � 0.30b 41.52 � 0.31a

.50 � 0.28ab 41.00 � 0.23b 41.40 � 0.26a

.10 � 0.21d 40.61 � 0.18b 40.11 � 0.22b

.30 � 0.17ab 41.24 � 0.14b 41.57 � 0.29a

rence at the p < 0.05 level.


Fig. 2. Changes in crumb firmness of control bread and MNG-containing breads during three day storage. Symbols: control; 0.5 g/100 g of 0.05 M NaOH MNG;0.5 g/100 g of 0.1 M NaOHMNG; 0.5 g/100 g of 0.2 M NaOHMNG; 1 g/100 g of 0.05 M NaOHMNG; 1 g/100 g of 0.1 M NaOHMNG;

1 g/100 g of 0.2 M NaOH MNG. Data present as mean of three independent replicates.

Table 3Maltose contents in dialysate (mmol/L) of in vitro digestion in a bread e a-amylase-dietary fiber system.

Bread Maltose content in dialysate (mmol/L)

15 min 30 min 60 min 120 min 180 min

Control 4.1 � 0.05a 4.3 � 0.13a 4.8 � 0.10a 4.9 � 0.05a 5.3 � 0.15a

MNG extracted with 0.05 mol/L NaOH0.5 g/100 g concentration 2.6 � 0.03b 2.8 � 0.05b 2.9 � 0.10c 3.1 � 0.03d 3.3 � 0.09c

1.0 g/100 g concentration 2.5 � 0.07b 2.6 � 0.03b 2.8 � 0.07c 3.0 � 0.01d 3.2 � 0.07c

MNG extracted with 0.1 mol/L NaOH0.5 g/100 g concentration 2.6 � 0.01b 2.7 � 0.10b 3.0 � 0.15bc 3.5 � 0.07bc 3.7 � 0.05b

1.0 g/100 g concentration 2.5 � 0.05b 2.7 � 0.05b 2.9 � 0.10bc 3.4 � 0.01c 3.6 � 0.01b

MNG extracted with 0.2 mol/L NaOH0.5 g/100 g concentration 2.7 � 0.07b 2.8 � 0.05b 3.3 � 0.13b 3.7 � 0.18b 4.0 � 0.05b

1.0 g/100 g concentration 2.5 � 0.13b 2.7 � 0.03b 3.0 � 0.10bc 3.5 � 0.15bc 3.8 � 0.18b

Data present as mean � S.E. of three independent replicates.aed different letters following means within the same column indicate a significant difference at the p < 0.05 level.


3.5. In vitro digestibility

Before food reaches the small intestine, enzymatic digestionwith pepsin and acidic condition in the stomach are factorseffecting the structure of food matrices. To simulate the conditionof gastrointestinal tract, the experimental design was set up to usepepsin and acidic condition for 30 min before applying a-amylasein a dialysis system. Generally, pepsin cleaves peptide bonds ofproteins to form a range of shorter peptides and amino acids(Brownlee, 2011), therefore the maltose and glucose levels detectedin a dialysis system were derived from a-amylase cleavage.

After digestion with a-amylase in a dialysis system for 15 min,MNG-containing breads showed significantly reduced amounts ofmaltose by 38% of control (Table 3) and decreased glucose by 37e

Table 4Glucose contents in dialysate (mmol/L) of in vitro digestion in a bread e a-amylase-dieta

Bread Glucose content in dialysate (mmol/L)

15 min 30 min

Control 3.6 � 0.15a 3.8 � 0.05a

MNG extracted with 0.05 mol/L NaOH0.5 g/100 g concentration 2.0 � 0.01bc 2.3 � 0.03bc

1.0 g/100 g concentration 1.9 � 0.01c 2.1 � 0.01c

MNG extracted with 0.1 mol/L NaOH0.5 g/100 g concentration 2.3 � 0.13b 2.4 � 0.06bc

1.0 g/100 g concentration 2.2 � 0.05bc 2.3 � 0.01bc

MNG extracted with 0.2 mol/L NaOH0.5 g/100 g concentration 2.3 � 0.07b 2.5 � 0.01b

1.0 g/100 g concentration 2.2 � 0.15bc 2.3 � 0.17bc

Data present as mean � S.E. of three independent replicates.aec different letters following means within the same column indicate a significant diffe


46% of control (Table 4). Maltose and glucose levels of 1 g/100 gMNG-containing breads were slightly lower than that of 0.5 g/100 gMNG-containing breads although there was no statistical signifi-cance (p > 0.05). At the end of study period (at 180 min), MNG-containing breads showed significantly lower amounts of maltose(by 23e39%) and glucose (by 33e40%) than did control bread.

3.6. Scanning electron microscopy

The scanning electron microscopy of fresh control bread showedtwo types of starch granules, spherical and oval shapes, protrudingfromglutenmatrix (Fig. 3). In contrast, freshMNG-containing breadsshowed smooth surface with starch granule adhesion in the glutenmatrix. Among MNG-containing breads, breads containing MNG

ry fiber system.

60 min 120 min 180 min

4.1 � 0.11a 4.3 � 0.17a 4.6 � 0.13a

2.5 � 0.10bc 2.6 � 0.09bc 2.9 � 0.07bc

2.3 � 0.03c 2.4 � 0.01c 2.7 � 0.03c

2.7 � 0.12b 2.9 � 0.07b 3.0 � 0.10b

2.5 � 0.15bc 2.7 � 0.18bc 2.9 � 0.03bc

2.8 � 0.09b 2.9 � 0.13b 3.0 � 0.10b

2.5 � 0.10bc 2.6 � 0.11bc 2.8 � 0.13bc

rence at the p < 0.05 level.


Fig. 3. Scanning Electron Micrographs (1000�) of control and MNG-containing breads. (A) control bread; (B) bread containing 0.5 g/100 g MNG extracted with 0.05 mol/L NaOH; (C)bread containing 1 g/100 g MNG extracted with 0.05 mol/L NaOH; (D) bread containing 0.5 g/100 g MNG extracted with 0.1 mol/L NaOH; (E) bread containing 1 g/100 g MNGextracted with 0.1 mol/L NaOH; (F) bread containing 0.5 g/100 g MNG extracted with 0.2 mol/L NaOH; (G) bread containing 1 g/100 g MNG extracted with 0.2 mol/L NaOH.


extracted with 0.05 mol/L NaOH had smooth surfactant with lessstarchprotruding from thematrix,with a less densematrix than thatof bread containing MNG extracted with 0.1 and 0.2 mol/L NaOH.

After in vitro digestion for 3.5 h, control bread had much porousappearance with less starch granule in the matrix indicating that a-amylase had high ability to digest starch granules (Fig. 4). Thisfinding is consistent with the highest amount of maltose andglucose after a-amylase digestion for 180 min in a dialysis system(Tables 3 and 4). MNG-containing breads had less porosity andmore compact appearance with retention of undigested starch


granules than that of control. Specifically, 1 g/100 g MNG-containing breads had undigested starch granules remainedintact with the matrix more than that of 0.5 g/100 g MNG-containing bread after a-amylase digestion for 180 min (Fig. 4).

4. Discussion

Physical properties of hydrocolloid-containing breads dependon the type and level of hydrocolloids added, as well as the level ofwater incorporation. Skendi, Biliaderis, Papageorgiou, and


Fig. 4. Scanning Electron Micrographs (1000�) of control and MNG-containing breads digested with porcine pancreatic a-amylase for 180 min in a dialysis system. (A) controlbread; (B) bread containing 0.5 g/100 g MNG extracted with 0.05 mol/L NaOH; (C) bread containing 1 g/100 g MNG extracted with 0.05 mol/L NaOH; (D) bread containing 0.5 g/100 g MNG extracted with 0.1 mol/L NaOH; (E) bread containing 1 g/100 g MNG extracted with 0.1 mol/L NaOH; (F) bread containing 0.5 g/100 g MNG extracted with 0.2 mol/LNaOH; (G) bread containing 1 g/100 g MNG extracted with 0.2 mol/L NaOH.


Izydorczyk (2010) reported that addition of b-glucan in wheat flourled to a decrease in loaf specific volume, in which the extent ofdecrease depending on b-glucan level. Other reports studying theeffect of xanthan gum-containing bread showed that adding gum athigh concentration exhibited too high resistance and consistencybatter contributed to a limited gas cell expansion during proofing(Lazaridou, Duta, Papageorgiou, Belc, & Biliaderis, 2007; Peressini,Pin, & Sensidoni, 2011). In the present study, MNG-containingbreads had more open crumb cells led to significantly higher loafvolume and loaf specific volume compared to that of control (Fig. 1


and Table 1). These results reflected that extracted MNGs enhancedincorporation of gases during mixing or increased CO2 retentionduring proofing. The results were in agreement with other reportsstudying the effect of hydrocolloids on bread properties; an in-crease in batter viscosity improves dough development and gasretention, thereby increasing loaf volume (Sciarini, Ribotta, Leon, &Perez, 2010).

Specific volume of both 0.5 g/100 g and 1 g/100 g MNG-containing breads was not significantly different. These resultsindicated that extracted MNGs at 1 g/100 g concentration might



bind a larger volume of water until breads was not fully expanded.However, the specific volume of 1 g/100 g MNG-containing breadswas significantly higher than that of control. This indicated thatMNG did not tightly bind water until gluten was not properly hy-drated. The results were opposite to other scientific studiesshowing that b-glucan has high water affinity and limits theavailable water within the paste mixture for the development ofthe gluten network, which contributed to reduced height, reducedloaf volume and increased crumb firmness (Cleary, Anderson, &Brennan, 2007; Gaosong & Vasanthan, 2000; Gill et al., 2002;Symons & Brennan, 2004). From the structure point of view, thedifferent characteristic of extracted MNGs may be beneficial forapplication of food product development.

After 24 h of storage, the moisture content of 1 g/100 g MNG-containing bread was significantly higher than that of 0.5 g/100 gMNG-containing bread (Table 2). This difference, however, was notfound on day 2 and day 3 of storage. These results indicate thatincreased concentration of MNG increased the ability of gum tohold the freewater but molecules were not tightly bound, thereforeexcess water was lost in long term.

Generally, hydrophilic gums tightly bind the free watercontributing to increased water retention, therefore bread crumbstays soft longer (Sharadanant & Khan, 2003). Changes in crumbsoftness and moisture loss are factors to indicate staling process ofbaked products during storage (Shittu, Aminu, & Abulude, 2009).The ideal moisture level of baked product related to the softness isbetween 35 and 40% (Shah, Shah, & Madamwar, 2006). The presentstudy showed that the rate of increased crumb firmness of MNG-containing breads was significantly lower than that of control.The moisture contents of MNG-containing breads during three-daystorage were higher than the ideal moisture level. Taken these re-sults together, it indicates that the water binding capacity ofextracted MNGs could prevent water loss during bread storage. Itwas proposed that viscous fiber has a larger water-holding capacitythan starch, thereby affecting decreased starch retrogradation andconsequently decreased crumb firmness (Purhagen, Sjoo, &Eliasson, 2012). The results in this study were in agreement withthat of Shittu et al. (2009) who reported that moisture loss andcrumb firmness during bread storage were best reduced when 1 g/100 g xanthan gum was added to bread formulation.

SEM of fresh control bread had starch granules that were pre-dominant within protein matrix (Fig. 3). Addition of extractedMNGs provided a continuous structure of starch granulesembedded into the protein matrix. The results were in agreementwith that of Brennan et al. (1996) who reported that gal-actomannan dispersed and mixed intimately with the starchgranules and protein matrix to become a continuous structureappearance.

The SEM of in vitro digestibility with a-amylase of MNG-containing breads showed more undigested starch granules thanthat of control (Fig. 4). In accordance with the results shown inTables 3 and 4, MNG-containing breads had significantly lowerlevels of maltose and glucose than did control. Taken together,these results suggest that extracted MNGs acted as a barrier toprevent a-amylase to contact starch granules. Plasma glucose levelsrise about 10 min after a meal as a result of the absorption of car-bohydrates ingested in the meal (Sudhir & Mohan, 2002). Accord-ing to oral glucose tolerance test pattern, the highest peak ofplasma glucose levels after carbohydrate consumption is at 30e60 min and gradually reduces to normal plasma level within120 min. In order to determine the durable ability of extractedMNGs to interfere a-amylase activity, bread e dietary fiber e a-amylase in a dialysis systemwas continuously run for 180 min. Thisstudy showed that the extracted MNGs in bread effectively pre-vented starch digestion contributing to less change of glucose and


maltose levels in a dialysate during 180 min. In contrast, a controlbread had gradually increased levels of glucose and maltose up to180 min. This finding is consistent with the previous report thatextracted MNGs interfered a-amylase activity in a starch solution e

a-amylase e dietary fiber system causing lower glucose content indialysate (Srichamroen & Chavasit, 2011b). The results of the pre-sent study were in agreement with a study indicated that hydro-colloid galactomannan may form a layer around starch granules,which could then shield the starch granules from enzyme attack(Slaughter et al., 2002). Brennan et al. (1996) also reported a lowerrate in the in vitro starch digestibility of guar galactomannan-containing bread when incubated with porcine pancreatic a-amylase compared to that of wheat bread.

5. Conclusion

Alkaline-extracted MNG added in bread formulation signifi-cantly increased loaf volume and specific volume. This is correlatedwith increased number of gas cells of the MNG-containing breads.Addition of extracted MNGs in bread formulation significantlyreducedmoisture loss and firmness of bread crumb after storage forthree days. The SEM of in vitro digestibility with a-amylase of MNG-containing breads showed less porosity and more undigestedstarch granules remained intact with the matrix. This finding wasconsistent with the low level of glucose and maltose. Specifically,MNG extracted with 0.05 mol/L NaOH had high potential to inter-fere a-amylase activity in starch digestion process. The significanceof this study indicates that the durable ability of extracted MNGs tointerfere a-amylase activity in solid matrix was up to 180 minregarding the time-experimental design.

Acknowledgments

The financial support, funding number R2553C194, from Nar-esuan University Fund, Thailand is gratefully acknowledged. Theauthor would like to thank Mrs. Prakaytip Kot-asa, Faculty of Sci-ence, Naresuan University for her SEM technical support.

References

Abu-Ghoush, M., Herald, T. J., Dowell, F., Xie, F., Aramouni, F. M., & Walker, C. (2008).Effect of antimicrobial agents and dough conditioners on the shelf-life exten-sion and quality of flat bread, as determined by near-infrared spectroscopy.International Journal of Food Science and Technology, 43, 365e372.

American Association of Cereal Chemists (AACC). (2000). Approved methods of theAACC (10th ed.). St Paul, MN: The Association (Method 44e15A).

Anderson, J. W., Akanji, A. O., & Randles, K. M. (2001). Treatment of diabetes withhigh-fibre diets. In G. A. Spiller (Ed.), CRC handbook of dietary fibre in humannutrition (3rd ed.) (pp. 373e400). New York: CRC Press.

Blackburn, N. A., Redfern, J. S., & Jarjis, H. (1984). The mechanism of action of guargum in improving glucose tolerance in man. Clinical Science, 66(3), 329e336.London.

Brennan, C. S., Blake, D. E., Ellis, P. R., & Schofield, J. D. (1996). Effects of guar gal-actomannan on wheat bread microstructure and on the in vitro and in vivodigestibility of starch in bread. Journal of Cereal Science, 24, 151e160.

Brownlee, I. A. (2011). The physiological roles of dietary fibre. Food Hydrocolloids, 25,238e250.

Ceriello, A. (2005). Postprandial hyperglycaemia and diabetes complications: is ittime to treat? Diabetes, 54, 1e7.

Cleary, L. J., Anderson, R., & Brennan, C. S. (2007). The behaviour and susceptibilityto degradation of high and low molecular weight barley b-glucan in wheatbread during baking and in vitro digestion. Food Chemistry, 102, 889e897.

Czuchajowska, Z., Pomeranz, Y., & Jeffers, H. C. (1989). Water activity and moisturecontent of dough and bread. Cereal Chemistry, 66, 128e132.

Gaosong, I., & Vasanthan, T. (2000). Effect of extrusion cooking on the primarystructure and water solubility of b-glucan from regular and waxy barley. CerealChemistry, 77, 396e400.

Gill, S., Vasanthan, T., Ooraikul, B., & Rossnagel, B. (2002). Wheat bread quality asinfluenced by the substitution of waxy and regular barley flours in their nativeand extruded forms. Journal of Cereal Science, 36, 219e237.

Heine, R. J., & Dekker, J. M. (2002). Beyond postprandial hyperglycaemia: metabolicfactors associated with cardiovascular disease. Diabetologia, 45, 461e475.


http://refhub.elsevier.com/S0023-6438(14)00251-5/sref1













































Huttner, E. K., & Arendt, E. K. (2010). Recent advances in gluten-free baking and thecurrent status of oats: a review. Trends in Food Science & Technology, 21, 303e312.

Lazaridou, A., Duta, D., Papageorgiou, M., Belc, N., & Biliaderis, C. G. (2007). Effects ofhydrocolloids on dough rheology and bread quality parameters in gluten-freeformulation. Journal of Food Engineering, 79, 1033e1047.

Peressini, D., Pin, M., & Sensidoni, A. (2011). Rheology and breadmaking perfor-mance of rice-buckwheat batters supplemented with hydrocolloids. Food Hy-drocolloids, 25, 340e349.

Purhagen, J. K., Sjoo, M. E., & Eliasson, A. C. (2012). Fibre-rich additives e the effecton staling and their function in free-standing and pan-baked bread. Journal ofthe Science of Food and Agriculture, 92, 1201e1213.

Rainbird, A. L., Low, A. G., & Zebrowska, T. (1984). Effect of guar gum on glucose andwater absorption from isolated loops of jejunum in conscious growing pigs.British Journal of Nutrition, 52(3), 489e498.

Rosell, C. M., Rojas, J. A., & Benedito de Barber, C. (2001). Influence of hydrocolloidson dough rheology and bread quality. Food Hydrocolloids, 15, 75e81.

Sabanis, D., & Tzia, C. (2011). Selected structural characteristics of HPMC-containinggluten free bread: a response surface methodology study for optimizing quality.International Journal of Food Properties, 14, 417e431.

Sciarini, L. S., Ribotta, P. D., Leon, A. E., & Perez, G. T. (2010). Influence of gluten freeflours and their mixtures on batter properties and bread quality. Food andBioprocess Technology, 3, 577e585.

Shah, A. R., Shah, R. K., & Madamwar, D. (2006). Improvement of the quality ofwhole wheat bread by supplementation of xylanase from Aspergillus foetidus.Bioresource Technology, 97, 2047e2053.

Sharadanant, R., & Khan, K. (2003). Effect of hydrophilic gums on the quality offrozen dough: II bread characteristics. Cereal Chemistry, 80(6), 773e780.


Shittu, T. A., Aminu, R. A., & Abulude, E. O. (2009). Functional effects of xanthangums on composite cassava wheat dough and bread. Food Hydrocolloids, 23(8),2254e2260.

Skendi, A., Biliaderis, C. G., Papageorgiou, M., & Izydorczyk, M. S. (2010). Effects oftwo barley b-glucan isolates on wheat flour dough and bread properties. FoodChemistry, 119(3), 1159e1167.

Slaughter, S. L., Ellis, P. R., Jackson, E. C., & Butterworth, P. J. (2002). The effect of guargalactomannan and water availability during hydrothermal processing on thehydrolysis of starch catalysed by pancreatic a-amylase. Biochimica et BiophysicaActa, 1571, 55e63.

Srichamroen, A., & Chavasit, V. (2011a). Rheological properties of extracted malvanut gum (Scaphium scaphigerum) in different conditions of solvent. Food Hy-drocolloids, 25(3), 444e450.

Srichamroen, A., & Chavasit, V. (2011b). In vitro retardation of glucose diffusion withgum extracted from malva nut seeds produced in Thailand. Food Chemistry, 127,455e460.

Sudhir, R., & Mohan, V. (2002). Postprandial hyperglycaemia in patients with type 2diabetes mellitus. Treatments in Endocrinology, 1(2), 106e116.

Symons, L. J., & Brennan, C. S. (2004). The influence of (1-3) (1-4)-b -D glucan-richfractions from barley on the physicochemical properties and in vitro reducingsugar release of white wheat breads. Journal of Food Science, 69(6), C463eC467.

Torsdottir, I., Alpsten, M., Anderson, H., & Einansson, S. (1989). Dietary guar gumeffects on postprandial blood glucose, insulin and hydroxyproline in humans.Journal of Nutrition, 119, 1925e1931.

Woolnough, J. W., Monro, J. A., Brennan, C. S., & Bird, A. R. (2008). Simulating humancarbohydrate digestion in vitro: a review of methods and the need for stan-dardization. International Journal of Food Science and Technology, 43, 2245e2256.












































































physical quality and in vitro starch digestibility of bread as affected by addition of extracted...

Documents