research article extrudability and consolidation of blends

Research ArticleExtrudability and Consolidation of Blends betweenCGM and DDGS

C J R Verbeek1 and Kurt A Rosentrater2

1School of Engineering University of Waikato Hamilton New Zealand2Department of Agricultural and Biosystems Engineering Iowa State University Ames IA USA

Correspondence should be addressed to C J R Verbeek jverbeekwaikatoacnz

Received 30 March 2016 Accepted 16 November 2016

Academic Editor Philip Eisenlohr

Copyright copy 2016 C J R Verbeek and K A Rosentrater This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

During the last decade the global biofuels industry has experienced exponential growth By-products such as high protein corngluten meal (CGM) and high fibre distillers dried grains with solubles (DDGS) have grown in parallel CGM has been shown to besuitable as a biopolymer the high fibre content of DDGS reduces its effectiveness although it is considerably cheaper In this studythe processing behaviour of CGM and DDGS blends was evaluated and resulting extrudate properties were determined Prior toprocessing urea was used as a denaturant DDGS CGM ratios of 0 33 50 66 and 100 were processed in a single screw extruderwhich solely used dissipative heating Blends containing DDGS were less uniformly consolidated and resulted in more dissipativeheating Blends showedmultiple glass transitions which is characteristic of mechanically compatible blends Transmission electronmicroscopy revealed phase separation on a microscale although distinct CGM or DDGS phases could not be identified On amacroscale optical microscopy suggested that CGM-rich blends were better consolidated supported by visual observations of amore continuous extrudate formed during extrusion Future work should aim to also characterize the mechanical properties ofthese blends to assess their suitability as either bioplastic feedstock or pelletized livestock feed

1 Introduction

Traditionally the motivations behind sustained researchin reducing dependence on polymers from petrochemicalsources were similar to those in energy research a decreasingfossil fuel supply with a corresponding price increase and awidespread awareness of sustainability [1] However todaythe focus may be more on the environmental side in light ofcurrent low oil prices

Polysaccharides and proteins could partially replacepetrochemical polymers and are often biodegradable [2]although this does not necessarily mean that they arerenewable Agropolymers are extracted from either plantsor animals and their use has long been recognised andmay be an innovative and sustainable approach to reducereliance on petrochemical polymers [2] Some of these poly-mers can be processed directly into thermoplastic materialshowever most require chemical modification to accountfor deficiencies such as brittleness water sensitivity and

low strength Common characteristics of agropolymers aretheir hydrophilicity fast degradation rate and sometimesunsatisfactory mechanical properties particularly in wetenvironments [3]

The benefit of agropolymers could be even greater if theyare by-products of other industries or processes One of themost frequently used materials for bioenergy production iscorn starch [4] Two main techniques are used to produceethanol wet milling and dry-grind processing For wetprocessing the primary end products are corn starch cornoil and ethanol obtained from separating the starch from therest of the kernel after milling [5] Additional end productsinclude corn gluten feed (CGF) corn gluten meal (CGM)corn germ meal and condensed fermented corn extractives(obtained after fermentation) [6] Dry grinding on theother hand has become the primary method for ethanolproduction in the US and uses the entire corn kernel [7]After fermentation the nonfermentable materials are usuallycombined dried and sold as ldquodistillers dried grains with

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2016 Article ID 4159258 11 pageshttpdxdoiorg10115520164159258

2 Advances in Materials Science and Engineering

solublesrdquo or DDGS Because of its high protein content CGMcan be used to produce thermoplastic materials [8] DDGSon the other hand is less expensive but is less likely to form athermoplastic

A major challenge for the development of thermoplas-tics from proteins is to rearrange protein structure duringprocessing this occurs in three steps [9 10] disruptingprotein-protein interactions plasticization and fixation Pro-tein secondary structures include 120572-helices 120573-sheets turnsand random coils [11] and chemical interactions such asdisulphide bonds hydrogen bonds van der Waals forcesand hydrophobic and electrostatic interactions maintainthe folded structures [12] During extrusion a considerableamount of mechanical energy is added to the materialwhich may affect final product properties The vast amountof possible chemical interactions combined with their heatsensitivity leaves a small window of feasible conditions forprocessing [13]

During extrusion material is conveyed through theextruderrsquos heated barrel inducing shear forces and increasingpressure along the barrel Feed composition screw speedbarrel temperature profile and feed rate as well as die sizeand shape are important process variables All of these willaffect screw fill specific mechanical energy (SME) torquepressure at the die residence time and product temperatureExtrusion requires transforming the protein into a melt-likestate implying processing above the proteinrsquos softening point(or glass transition temperature) which is often very highfor dehydrated proteins To avoid degradation additives arerequired for thermoplastic extrusion Furthermore high pro-cessing temperatures and specific mechanical energy inputcan cause excessive degradation and cross-linking [13 14]

Di Gioia et al studied the effectiveness of various addi-tives on CGM processing using batch mixing and com-pression moulding but found that processing CGM witheither water or glycerol resulted in materials that were notvery cohesive [15ndash17] Aqueous urea is a well-known proteindenaturant unfolds protein structures and is an effectiveadditive to promote protein consolidation [8] It disruptsprotein secondary structure which could ultimately affecthow chains interact with each other as well as with water [18ndash22]

The chemical composition of DDGS and CGM is vastlydifferent with CGM being much richer in protein (sim67versus 34 resp)The higher carbohydrate content of DDGS(mainly cellulose) may impede the formation of a thermo-plastic material however it is favourable to include someDDGS to reduce cost [23] The objective of this research wasto assess the effect of partially replacing CGMwith DDGS bymonitoring processability consolidation thermal propertiesand morphology of the blends

2 Materials and Methods

21 Materials Corn gluten meal was obtained from Con-sumers Supply Distributing (Sioux City IA USA) whileDDGS was procured from VeraSun Energies (Aurora SDUSA) after having the lipids removed by solvent extraction

Table 1 Composition of the raw protein sources used in the studylowast

CGM DDGSDry matter () 908 980Crude protein ( db) 674 340Crude lipid ( db) 22 27Carbohydrate ( db) 281 585Neutral detergent fiber ( db) 57 501Starch ( db)lowast 15 5

Ash ( db) 23 48lowastAnalysis performed at Servitech Laboratories Hastings NE USA

[24] Composition of each of these protein meals is providedin Table 1

22 Protein Modification Prior to processing CGM andDDGS were mixed with 10 g urea (dissolved in 50 g water)per 100 g of protein meal Materials were thoroughly mixedfor 30min in a rotating mixer and then sealed in plasticcontainers and left over night to equilibrate

23 Experimental Design Both the DDGS and the CGMprotein meals were modified by combining 100 parts proteinmeal 50 parts water and 10 parts urea 24 h prior to pro-cessing Blends were formulated (on a mass basis) to consistof DDGS CGM ratios of 0 1 1 2 1 1 2 1 and 1 0 Tworeplicate extrusion runs per each of the five blends were usedfor a total of 10 extrusion runs

24 Extrusion Processing After modification the proteinsources were blended at the specified ratios and wereextruded in a single screw extruder (Rietz Extructor BepexInternational LLC Minneapolis MN USA) using frictionalheating aloneThe screw configuration is shown in Figure 1(a)and the extruder has an LDof 376Thedie plate (Figure 1(b))consisted of 6 2mm diameter orifices equally spaced witha total open area of 189mm2 The extruderrsquos barrel hasthree sections of which the front section was fitted with twothermocouples at the entry (1198792) and the die (1198791) Powerconsumption was continuously monitored using a powermeter from HIOKI (Model 3196 HIOKI EE CorporationNagano Japan) [25]

Extrusions were carried out in duplicate for each blendcombination (ie 119899 = 2 for each treatment) followinga completely randomized order The input feed rate wasset to ensure steady state operation of the extruder Afterprocessing the extrudates were cooled to room temperaturedried at 40∘C for 24 h and then stored in sealed polyethylenebags at room temperature until further analysis

25 Analysis Particle size of the raw andmodified blendswasdetermined using a particle size analyser (Camsizer HoribaInstruments Irvine CA USA)

Heat flows and glass transition temperatures were deter-mined using a differential scanning calorimeter (DSC 822e

Advances in Materials Science and Engineering 3

DieZone 2 Zone 1

(a)

typical of 6 holes

3025

25

2mm diameter hole

16 cm diameter6 cm diameter

60∘

(b)

Figure 1 (a) Extruder barrel configuration (b) die plate schematic

Mettler-Toledo Inc Columbus OH USA) using hermeti-cally sealed pans and scanning between 20 and 140∘Cat a scanrate of 50∘C under nitrogen gas

Consolidationwas assessed based on optical images at 10xmagnification Optical images were collected using a digitalmicroscope (Digital Blue QX5) fitted with a digital cameraEach image was adjusted for brightness and contrast usingImageJ software ImageJ was used for edge detection usingcolour images after which they were converted to binaryimages Based on a circular section of the image the per-centage black and white areas can be calculated correspond-ing to consolidated and nonconsolidated areas

Transmission electron microscope images were takenusing a JEOL JEM2100F field emission instrument Sampleswere imbedded in epoxy after osmium tetroxide and glu-taraldehyde fixation

Moisture contents of all materials were determined bydrying in a laboratory oven at 60∘C for 24 h

3 Results and Discussion

31 Raw Materials DDGS had a larger average particle size(071mm) compared to CGM (051mm) and blending themin any proportion let CGM take up the void space betweenDDGS particles At larger magnification the more irregularshaped particles were evident in DDGS (Figure 2)

DDGS was low in starch but very high in fibre (watersoluble cellulose) whereas CGM had very little fibre bothhad similar lipid content CGM had about double the proteincontent and one would expect it to be processed into athermoplastic easier while DDGSrsquo high cellulose contentwould likely require more energy for processing

Both materials were effectively already a blend (mor-phology shown later) and blending them further changedthe overall of proportion of protein starch and celluloseFor example in a 1 2 ratio CGM DDGS blend the proteincontent drops to about 45 with nearly the same amount ofcarbohydrates

The proteinmeals considered here are composed not onlyof corn protein but also of lipids fibres and other carbo-hydrates which all may have different thermal events RawCGM and DDGS both showed an endothermic event at 86∘Cand was not melting of any crystalline regions (Figure 3)The endotherm at 86∘C is probably due to amorphous chainstightly packing over time [26]When heated chain relaxationoccurs leading to an endothermic event Adding urea andwater had the same effect as heating and no endotherm wasobserved in the denatured raw materials due to the addedchain mobility brought about the plasticizing effect of waterin addition to the effect of urea

Untreated and unprocessed proteins typically have a veryhigh glass transition temperature in the order of 200∘CLiterature suggests that CGM has a 119879119892 of 178∘C whichwill overlap with water evaporation (endothermic peak) andis better detected using DMA Urea is a strong proteindenaturant disrupting hydrogen bonding between proteinchains After denaturing (and plasticization) the 119879119892 of CGMdropped to 109∘C and 60∘C for DDGS (Table 2) Dry DDGShas been shown to have a 119879119892 in the region of 136∘C anddepends strongly on water content [27] Although it appearsthat DDGS has a second transition at about 120 it is morelikely part of water evaporation

32 Extrusion After denaturing and plasticization the119879119892 (orsoftening point) of the materials is low enough to allow forextrusion and consolidation Power consumption curves foreach blend generally followed similar trends with distinctchanges after each chamber became completely filled (Fig-ure 4) After the third chamber filled completely peak powerwas reached after which the power consumption decreasedas the first barrel started emptying again All blends showedpower consumption increasing over time due to frictionalheating Providing enough heat could lead to structuralmodification of the protein and if plasticized may lead tomore power required for flow (as opposed to individualparticles moving for compressed powders)


CGM

DDGS

times10 times60

1 2

1 1

2 1

Figure 2 Optical images of CGM and DDGS particles at times10 and times60 magnification before denaturing or extrusion

Hea

t flow

(Wg

)

DDGSCGM

Raw

Denatured

40 60 80 100 120 14020Temperature (∘C)

minus3

minus25

minus2

minus15

minus1

minus05

0

05

1

15

2

Figure 3 DSC thermograms of CGM and DDGS before and after denaturing


Friction

Fillingzone 1

Fillingzone 2

Fillingzone 3

Barrelempty

Start oftrial

Barrelemptying

Peakpower

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

Figure 4 Generalized power consumption curve indicating different regions of power consumption during extrusion

Table 2 Thermal events for CGM DDGS and blends thereof

Blend 119879endo 1198791198921 1198791198922(∘C)

CGM raw 86DDGS raw 86CGM denatured 109DDGS denatured 60CGM DDGS 2 1 raw 89CGM DDGS 2 1 denatured 110CGM DDGS 2 1 extruded 60 108CGM DDGS 1 1 raw 89CGM DDGS 1 1 denatured 110CGM DDGS 1 1 extruded 53 100CGM DDGS 1 2 raw 92CGM DDGS 1 2 denatured 112CGM DDGS 1 2 extruded 56 102

For CGM the rise in power consumption during thefilling of each barrel section was much faster compared toDDGSAlthough the time it took for each barrel to fill was notexactly the same the time it took to reach maximum powerwas approximately the same (Figure 5) The higher proteinfraction in CGM is probably the cause for the more rapidpower increase as a viscoelastic melt is formed Howeverif this melt is pseudoplastic (most thermoplastics are) adrop in power consumption will be observedThis behaviourwas very evident in CGM and much less so for DDGS asexpected

The difference between blends wasmuch less pronouncedwith the rate of power increase being very similar in the firsttwo zones It should be noted that these curves have not beencorrected for mass flow (ie SME) and the absolute value ofpower consumption is therefore insignificant in these figures

What is evident from these curves however is that atthe end of each zone filling stage there is a drop in powerrequirement and thiswas ascribed to the pseudoplastic nature

of the formed melt It was observed that DDGS had a rela-tively smaller drop in power consumption at the end of zonesone and two Furthermore blends with increasing DDGSalso showed less pseudoplasticity This could be explainedby the fact that DDGS contains significantly more cellulosicmaterial which cannot be plasticized as the protein fraction

Integrating the power consumption data to determinethe area under each power curve provided total energy con-sumed Dividing total energy consumption (accounting forfriction) by mass flow rate provided the specific mechanicalenergy consumption (SME)The greater the SME the greaterthe power input per unit of product some of this power wasconverted into frictional heating between the extruder screwand the material

DDGS required more than twice the average power perkilogram of material than CGM (715 kJkg versus 335 kJkg)for extruding (Figure 6) This would indicate that DDGSdid not form a semicontinuous pseudoplastic melt This wasalso supported by morphology observations presented laterThe peak power requirement per kilogrammaterial showed asimilar trend with increasing maximum power with increas-ing DDGS content One would conclude that DDGS partiallyacts as a filler and disrupts the formation of amelt if includedin a too great proportion

Temperature rise in the extruder barrel both zone 1 (cen-tral extruder chamber) and zone 2 (chamber at which thematerial exited the die) increased over time (Figure 7)Zone 2 always had a much higher temperature responsebecause that was the chamber where themajority of frictionalenergy was imparted to the dough zone 1 was primarily azone for material transfer (Figure 1) CGM appeared to heatmore rapidly than did DDGS As DDGS level in the blendincreased the maximum temperature in the extruder (bothzone 1 and zone 2) had a curvilinear response so that asDDGS level increased processing temperatures in generaldeclined

The modest temperature increase associated with DDGSprocessing is indicative of its lack of melt formation effec-tively requiring less dissipative heating However processing


CGM

DDGS

1 2

1 1

2 1

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

Figure 5 Power consumption during extrusion of CGM and DDGS blends

0

200

400

600

800

1000

1200

1400

Pow

er (k

Jkg)

50 1000Percentage DDGS ()

R2= 07619

R2= 07619

Figure 6 Power consumption during extrusion of CGM and DGS as a function of DDGS content ◻ peak power I average power

DDGS required more power suggesting that in the caseof CGM where less power (lower viscosity) was required apseudoplastic melt had formed

33 Consolidation Figure 8 shows longitudinal and radialimages of the extrudate as well as images from the materialdirectly behind the die Relatively poor consolidation wasachieved even from pure CGM which is slightly at oddswith previous work However these materials were notinjection moulded into test pieces but analysed directly afterextrusion Furthermore the extruder setup precluded highpressure build up typically required for consolidation Thecross-sectional images were used to quantify the degree ofconsolidation by using image analysis assuming black areascorresponded to consolidated material (Figure 9) Completesubstitution of DDGS for CGM reduced the consolidation

from about 60 to between 40 and 45 It was thought thatthe nonprotein fraction in DDGS would be the main reasonfor this reduction as the fibre content will not be able tobe consolidated as part of the polymer matrix Despite thisa semicontinuous extrudate still formed suggesting enoughconsolidation required for bioplastic formation

Pure DDGS consolidated poorly compared to CGMalthough all the longitudinal images had a rather roughsurface appearance getting progressively worse from 100CGM to 100 DDGS The poor surface appearance is likelydue to the sudden pressure drop and high temperature at theextruder die causing some degree of separation due to steamevaporation Considering the images of the material behindthe die they appeared to be much better consolidated How-ever adding DDGS to CGM did decrease the consolidatedappearance of the material


50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)

20 40 60 80 1000Percentage DDGS

(c)

Figure 7 Temperature of zone 1 (1198791) and zone 2 (1198792) over time for extruding (a) CGM and (b) DDGS (c) Maximum temperature duringextrusion for blends (I zone 1 998779 zone 2)

These results are consistent with the power consumptiondata which indicated that extruding CGMor blends contain-ing more CGM than DDGS required less power because ofthe formation of a pseudoplastic melt It would follow thatthis happens in parallel to consolidation

It is important to remember that neither CGM norDDGS are pure substances and are blends of proteins andcarbohydrates (Table 1)Themorphology of CGMandDDGSafter denaturing and extrusion are still heterogeneous at amicroscale For TEM analysis samples were stained withosmium tetroxide which preferentially stains carbohydratesover proteins (Figure 10) CGM appears to have more thread-like features compared to DDGS DDGS had comparablydarker regions that would be consistent to its higher carbo-hydrate content For both materials circular (or spherical)regions were present surrounded with a thin layer of whatappears to be protein

In the 1 1 blend the morphology appears to be muchmore homogenous with a distinct absence of the sphericalinclusions It would appear that extrusion has led to somedegree of dispersion of the various polymeric phases Theblend is clearly still phase separated on a microscale but noevidence of poor interfacial adhesionwas foundWith TEM itwas difficult to assess consolidation as the magnification wastoo high

34Thermal Properties Blending polymers typically leads tospecific thermal properties an immiscible blend will showa glass transition temperature akin to each phase while amiscible blend will only have one 119879119892 (assuming both phasesare amorphous) proportional to the composition of the blendFor a partially miscible system or a compatible blend morethan one 119879119892 is still observed but the two 119879119892s move closertogether as compatibility is increased


Longitudinal Radial Extruder internal

CGM

DDGS

1 2

1 1

2 1

Figure 8 Optical images at times60 magnification of CGM and DDGS and their blends in the ratios shown

The thermal properties of CGM and DDGS are complexas both these materials are in fact blends of different proteinfractions as well as carbohydrates each of these could giverise to a distinct 119879119892 (Figure 11) CGM and DDGS bothshowed thermal transitions thought to be associated withthermal transitions of differentmaterials in each feed proteinFor CGMDDGS blends before any modification the sameendotherm at approximately 86∘C was observed Because of

water evaporation (endotherm obscuring other events) noglass transition was observed That is not to say that therewere none but it is likely that the 119879119892s for CGM and DDGSare both closer to 200∘C After adding water and urea as adenaturant the endothermic peak thought to be an agingpeak disappears because of the increased chain mobility Forthe same reason a glass transition at around 110∘C is observedfor all the denatured blends before extrusion


30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)

20 40 60 80 1000Percentage DDGS ()

R2= 07261

Figure 9 Percentage consolidation as a function of DDGS content

Table 3 Moisture content of CGM and DDGS before and afterextrusion based on adding water and urea in the amounts shownper 100 g CGM or DDGS

CGM DDGSDry matter (g)lowast 908 98Initial water (g)lowast 92 2Added water (g)lowast 50 50Urea (g)lowast 10 10Moisture ()

Before extrusion 37 325After extrusion 298 260

lowastPer 100 g CGM or DDGS

Extrusion led to further changes in the thermal behaviourof the blends In all cases two 119879119892s were observed one atsim60 and one at sim100∘C Extrusion will lead to disruptionof existing chain interactions and to the formation of newinteractions Both these processes will lead to changes inthermal behaviour of the blend For the CGMDDGS blendsit would appear that the observed 119879119892s represent the 119879119892s ofCGM and DDGS respectively suggesting that these form anincompatible blend Based on the morphology one wouldconclude that the blends are certainly not miscible on amolecular scale but interfacial adhesion is probably adequatefor the blend to behave as a compatible blend Based on theseresults it is likely that the properties of these blends could befurther improved with the incorporation of other additivesthat would promote miscibility

Another factor not considered explicitly here is moisturecontent It is well known that water is a plasticizer forboth proteins and carbohydrates The apparent indifferencebetween the 119879119892 values of the blends could be due to water(Table 3) Increasing water content will reduce the 119879119892 signif-icantly and for the current work extruding CGM led to aslightly highermoisture loss compared toDDGS Blends withmore CGM could therefore have a slightly higher 119879119892 than ifall the blends had the same moisture content

4 Conclusions

Corn-based protein sources consist of a blend of carbohy-drates and protein CGMhas a higher proportion protein andis easier to consolidate into a monolithic material comparedto DDGS which contains almost twice as much celluloseas CGM while CGM is rich in protein a requirement forsuccessful thermoplastic processing This study has shownthat thermoplastics based on CGM can be made cheaper byfilling with DDGS Since both thesematerials are corn-baseda semicompatible blend is formed but using a majority ofDDGS led to higher power requirements for processing andwas detrimental to consolidation

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

The authors would like to thank the following people forthe invaluable contribution to completing the experimental


(a) (b) (c)

Figure 10 TEM Images of (a) CGM (b) DDGS and (c) CGM DDGS 1 1 Scale bar represents 10 120583m

After processingBefore processingRaw blend

40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)

Figure 11 DSCThermograms of blends between CGM and DDGS (a) minus2 1 (b) minus1 1 (c) minus1 2


work Sharon Nichols Christine Wood Kamal Mjoun andTony Nielson Also the authors wish to acknowledge help ofChris van der Merwe from the Laboratory for Microscopyand Microanalysis University of Pretoria for his technicalassistance on the TEM

References

[1] A Gandini ldquoPolymers from renewable resources a challengefor the future of macromolecular materialsrdquo Macromoleculesvol 41 no 24 pp 9491ndash9504 2008

[2] F Chivrac E Pollet and L Averous ldquoProgress in nano-bio-composites based on polysaccharides and nanoclaysrdquoMaterialsScience and Engineering R Reports vol 67 no 1 pp 1ndash17 2009

[3] C J RVerbeek and JM Bier ldquoSynthesis and characterization ofthermoplastic agro-polymersrdquo inHandbook of Applied Biopoly-mer Technology S K Sharma andAMudhoo Eds pp 197ndash242RSC Publishing 2011

[4] K Liu and K A Rosentrater Distillers Grains ProductionProperties and Utilization Taylor and FrancisCRC Press BocaRaton Fla USA 2011

[5] L A Johnson and J BMay ldquoWetmilling the basis for corn bio-refineriesrdquo inCorn Chemistry and Technology P JWhite and LA Johnson Eds pp 449ndash495 American Association of CerealChemists St Paul Minn USA 2003

[6] D D Loy and K NWright ldquoNutritional properties and feedingvalue of corn and its by-productsrdquo in Corn Chemistry andTechnology P J White and L A Johnson Eds pp 571ndash604American Association of Cereal Chemists Saint Paul MinnUSA 2003

[7] R J Bothast and M A Schlicher ldquoBiotechnological processesfor conversion of corn into ethanolrdquo Applied Microbiology andBiotechnology vol 67 no 1 pp 19ndash25 2005

[8] K L Pickering C J R Verbeek and C Viljoen ldquoThe effectof aqueous urea on the processing structure and properties ofCGMrdquo Journal of Polymers and the Environment vol 20 no 2pp 335ndash343 2012

[9] L A De Graaf ldquoDenaturation of proteins from a non-foodperspectiverdquo Journal of Biotechnology vol 79 no 3 pp 299ndash306 2000

[10] J K Sears and J R Darby ldquoMechanism of plasticiser actionrdquo inThe Technology of Plasticizers J K Sears and J R Darby Edspp 33ndash77 John Wiley amp Sons New York NY USA 1982

[11] J S Richardson ldquoThe anatomy and taxonomy of protein struc-turerdquo Advances in Protein Chemistry vol 34 pp 167ndash339 1981

[12] D Whitford Proteins Structure and Function John Wiley andSons Chichester UK 2005

[13] C J R Verbeek and L E Van Den Berg ldquoExtrusion processingand properties of protein-based thermoplasticsrdquoMacromolecu-lar Materials and Engineering vol 295 no 1 pp 10ndash21 2010

[14] H C Huang T C Chang and J Jane ldquoMechanical andphysical properties of protein-starch based plastics produced byextrusion and injection moldingrdquo Journal of the American OilChemistsrsquo Society vol 76 no 9 pp 1101ndash1108 1999

[15] L di Gioia B Cuq and S Guilbert ldquoEffect of hydrophilic plas-ticizers on thermomechanical properties of corn gluten mealrdquoCereal Chemistry vol 75 no 4 pp 514ndash519 1998

[16] L Di Gioia B Cuq and S Guilbert ldquoPlasticization of corngluten meal and characterization of the blendsrdquo Macromolec-ular Symposia vol 144 no 1 pp 365ndash369 1999

[17] L Di Gioia and S Guilbert ldquoCorn protein-based thermoplasticresins effect of some polar and amphiphilic plasticizersrdquo Jour-nal of Agricultural and Food Chemistry vol 47 no 3 pp 1254ndash1261 1999

[18] L A Danzer H Ades and E D Rees ldquoThe helical content ofzein a water insoluble protein in non-aqueous solventsrdquo Bio-chimica et Biophysica Acta (BBA)mdashProtein Structure vol 386no 1 pp 26ndash31 1975

[19] A Esen ldquoA proposed nomenclature for the alcohol-solubleproteins (zeins) of maize (Zea mays L)rdquo Journal of CerealScience vol 5 no 2 pp 117ndash128 1987

[20] H C Nielsen J W Paulis C James and J S Wall ldquoExtractionand structure studies on corn glutelin proteinsrdquo Cereal Chem-istry Journal vol 47 no 5 pp 501ndash512 1970

[21] J S Wall L A Cooker and J A Bietz ldquoStructure and origin ofmaize endosperm alcohol-insoluble glutelinrdquo Journal of Agri-cultural and Food Chemistry vol 36 no 4 pp 722ndash728 1988

[22] S Sanchez Del Angel E Moreno Martınez and M A ValdiviaLopez ldquoStudy of denaturation of corn proteins during storageusing differential scanning calorimetryrdquo Food Chemistry vol83 no 4 pp 531ndash540 2003

[23] K A Rosentrater and C J R Verbeek ldquoProcessibility of cornprotein blends and resulting properties of the extrudatesrdquo inProceedings of the Quality of Life Through Chemical Engineer-ing (Chemeca rsquo12) pp 1127ndash1136 Wellington New ZealandSeptember 2012

[24] J A Saunders and K A Rosentrater ldquoProperties of solventextracted low-oil corn distillers dried grains with solublesrdquo Bio-mass and Bioenergy vol 33 no 10 pp 1486ndash1490 2009

[25] K Mjoun and K A Rosentrater ldquoExtruded aquafeeds contain-ing distillers dried grains with solubles effects on extrudateproperties and processing behaviourrdquo Journal of the Science ofFood and Agriculture vol 91 no 15 pp 2865ndash2874 2011

[26] J M Bier C J R Verbeek and M C Lay ldquoThermal transitionsand structural relaxations in protein-based thermoplasticsrdquoMacromolecular Materials and Engineering vol 299 no 5 pp524ndash539 2014

[27] A R P Kingsly and K E Ileleji ldquoGlass transition behavior ofcorn distillers dried grains with solubles (DDGS)rdquo Journal ofCereal Science vol 54 no 3 pp 332ndash338 2011

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Journal ofNanomaterials


solublesrdquo or DDGS Because of its high protein content CGMcan be used to produce thermoplastic materials [8] DDGSon the other hand is less expensive but is less likely to form athermoplastic

A major challenge for the development of thermoplas-tics from proteins is to rearrange protein structure duringprocessing this occurs in three steps [9 10] disruptingprotein-protein interactions plasticization and fixation Pro-tein secondary structures include 120572-helices 120573-sheets turnsand random coils [11] and chemical interactions such asdisulphide bonds hydrogen bonds van der Waals forcesand hydrophobic and electrostatic interactions maintainthe folded structures [12] During extrusion a considerableamount of mechanical energy is added to the materialwhich may affect final product properties The vast amountof possible chemical interactions combined with their heatsensitivity leaves a small window of feasible conditions forprocessing [13]

During extrusion material is conveyed through theextruderrsquos heated barrel inducing shear forces and increasingpressure along the barrel Feed composition screw speedbarrel temperature profile and feed rate as well as die sizeand shape are important process variables All of these willaffect screw fill specific mechanical energy (SME) torquepressure at the die residence time and product temperatureExtrusion requires transforming the protein into a melt-likestate implying processing above the proteinrsquos softening point(or glass transition temperature) which is often very highfor dehydrated proteins To avoid degradation additives arerequired for thermoplastic extrusion Furthermore high pro-cessing temperatures and specific mechanical energy inputcan cause excessive degradation and cross-linking [13 14]

Di Gioia et al studied the effectiveness of various addi-tives on CGM processing using batch mixing and com-pression moulding but found that processing CGM witheither water or glycerol resulted in materials that were notvery cohesive [15ndash17] Aqueous urea is a well-known proteindenaturant unfolds protein structures and is an effectiveadditive to promote protein consolidation [8] It disruptsprotein secondary structure which could ultimately affecthow chains interact with each other as well as with water [18ndash22]

The chemical composition of DDGS and CGM is vastlydifferent with CGM being much richer in protein (sim67versus 34 resp)The higher carbohydrate content of DDGS(mainly cellulose) may impede the formation of a thermo-plastic material however it is favourable to include someDDGS to reduce cost [23] The objective of this research wasto assess the effect of partially replacing CGMwith DDGS bymonitoring processability consolidation thermal propertiesand morphology of the blends

2 Materials and Methods

21 Materials Corn gluten meal was obtained from Con-sumers Supply Distributing (Sioux City IA USA) whileDDGS was procured from VeraSun Energies (Aurora SDUSA) after having the lipids removed by solvent extraction

Table 1 Composition of the raw protein sources used in the studylowast

CGM DDGSDry matter () 908 980Crude protein ( db) 674 340Crude lipid ( db) 22 27Carbohydrate ( db) 281 585Neutral detergent fiber ( db) 57 501Starch ( db)lowast 15 5

Ash ( db) 23 48lowastAnalysis performed at Servitech Laboratories Hastings NE USA

[24] Composition of each of these protein meals is providedin Table 1

22 Protein Modification Prior to processing CGM andDDGS were mixed with 10 g urea (dissolved in 50 g water)per 100 g of protein meal Materials were thoroughly mixedfor 30min in a rotating mixer and then sealed in plasticcontainers and left over night to equilibrate

23 Experimental Design Both the DDGS and the CGMprotein meals were modified by combining 100 parts proteinmeal 50 parts water and 10 parts urea 24 h prior to pro-cessing Blends were formulated (on a mass basis) to consistof DDGS CGM ratios of 0 1 1 2 1 1 2 1 and 1 0 Tworeplicate extrusion runs per each of the five blends were usedfor a total of 10 extrusion runs

24 Extrusion Processing After modification the proteinsources were blended at the specified ratios and wereextruded in a single screw extruder (Rietz Extructor BepexInternational LLC Minneapolis MN USA) using frictionalheating aloneThe screw configuration is shown in Figure 1(a)and the extruder has an LDof 376Thedie plate (Figure 1(b))consisted of 6 2mm diameter orifices equally spaced witha total open area of 189mm2 The extruderrsquos barrel hasthree sections of which the front section was fitted with twothermocouples at the entry (1198792) and the die (1198791) Powerconsumption was continuously monitored using a powermeter from HIOKI (Model 3196 HIOKI EE CorporationNagano Japan) [25]

Extrusions were carried out in duplicate for each blendcombination (ie 119899 = 2 for each treatment) followinga completely randomized order The input feed rate wasset to ensure steady state operation of the extruder Afterprocessing the extrudates were cooled to room temperaturedried at 40∘C for 24 h and then stored in sealed polyethylenebags at room temperature until further analysis

25 Analysis Particle size of the raw andmodified blendswasdetermined using a particle size analyser (Camsizer HoribaInstruments Irvine CA USA)

Heat flows and glass transition temperatures were deter-mined using a differential scanning calorimeter (DSC 822e


DieZone 2 Zone 1

(a)

typical of 6 holes

3025

25

2mm diameter hole


60∘

(b)














CGM

DDGS

times10 times60

1 2

1 1

2 1


Hea

t flow

(Wg

)

DDGSCGM

Raw

Denatured

40 60 80 100 120 14020Temperature (∘C)

minus3

minus25

minus2

minus15

minus1

minus05

0

05

1

15

2



Friction

Fillingzone 1

Fillingzone 2

Fillingzone 3

Barrelempty

Start oftrial

Barrelemptying

Peakpower

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)



Blend 119879endo 1198791198921 1198791198922(∘C)











CGM

DDGS

1 2

1 1

2 1

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)


0

200

400

600

800

1000

1200

1400

Pow

er (k

Jkg)


R2= 07619

R2= 07619







50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)


(c)








CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




DieZone 2 Zone 1

(a)

typical of 6 holes

3025

25

2mm diameter hole


60∘

(b)














CGM

DDGS

times10 times60

1 2

1 1

2 1


Hea

t flow

(Wg

)

DDGSCGM

Raw

Denatured

40 60 80 100 120 14020Temperature (∘C)

minus3

minus25

minus2

minus15

minus1

minus05

0

05

1

15

2



Friction

Fillingzone 1

Fillingzone 2

Fillingzone 3

Barrelempty

Start oftrial

Barrelemptying

Peakpower

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)



Blend 119879endo 1198791198921 1198791198922(∘C)











CGM

DDGS

1 2

1 1

2 1

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)


0

200

400

600

800

1000

1200

1400

Pow

er (k

Jkg)


R2= 07619

R2= 07619







50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)


(c)








CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




CGM

DDGS

times10 times60

1 2

1 1

2 1


Hea

t flow

(Wg

)

DDGSCGM

Raw

Denatured

40 60 80 100 120 14020Temperature (∘C)

minus3

minus25

minus2

minus15

minus1

minus05

0

05

1

15

2



Friction

Fillingzone 1

Fillingzone 2

Fillingzone 3

Barrelempty

Start oftrial

Barrelemptying

Peakpower

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)



Blend 119879endo 1198791198921 1198791198922(∘C)











CGM

DDGS

1 2

1 1

2 1

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)


0

200

400

600

800

1000

1200

1400

Pow

er (k

Jkg)


R2= 07619

R2= 07619







50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)


(c)








CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Friction

Fillingzone 1

Fillingzone 2

Fillingzone 3

Barrelempty

Start oftrial

Barrelemptying

Peakpower

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)



Blend 119879endo 1198791198921 1198791198922(∘C)











CGM

DDGS

1 2

1 1

2 1

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)


0

200

400

600

800

1000

1200

1400

Pow

er (k

Jkg)


R2= 07619

R2= 07619







50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)


(c)








CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




CGM

DDGS

1 2

1 1

2 1

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)

50 100 150 200 2500Time (s)

0

500

1000

1500

2000

2500

3000

3500

Pow

er co

nsum

ptio

n (W

)


0

200

400

600

800

1000

1200

1400

Pow

er (k

Jkg)


R2= 07619

R2= 07619







50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)


(c)








CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

100Te

mpe

ratu

re (∘

C)

(a)

50 100 150 200 250 3000Time (s)

0

10

20

30

40

50

60

70

80

90

Tem

pera

ture

(∘C)

(b)

0

20

40

60

80

100

120

140

Tem

pera

ture

(∘C)


(c)








CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





CGM

DDGS

1 2

1 1

2 1





30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




30

35

40

45

50

55

60

65

70

Con

solid

atio

n (

)


R2= 07261








4 Conclusions


Competing Interests


Acknowledgments



(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)



40 60 80 100 120 14020Temperature (∘C)

minus3

minus2

minus1

0

1

2

3

Hea

t flow

(Wg

)

(a)


40 60 80 100 120 14020Temperature (∘C)

minus2

minus15

minus1

minus05

0

05

1

15

2

25

Hea

t flow

(Wg

)

(b)


40 60 80 100 120 14020Temperature (∘C)

minus4

minus3

minus2

minus1

0

1

2

Hea

t flow

(Wg

)

(c)




References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





References



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article extrudability and consolidation of blends

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