Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Traditional instruments used to evaluate dough and/or gluten rheological properties do not provide unambiguous separation of elastic and viscous behaviors. Thus, it has been difficult to determine intercultivar variations in the pure elastic properties of gluten and in turn how these variations are related to dough physical properties and breadmaking performance. Recovery after shear creep and cyclic large deformation tensile testing are two ways to decouple elastic and viscous effects. A large variation in the recoverable shear strain preceding creep (~ 7.2% to ~28%) was seen for Glutomatic-obtained glutens from 15 U.S. popular wheat cultivars with varying HMW subunits. Zeleny sedimentation values ranged from 29 to 57 ml for 12 hard wheat cultivars and from 15 to 22 ml for three soft wheat cultivars. The recoverable strain ranged from 71 to 93% of the creep deformation. The tensile force at 500% deformation ranged from 0.12 to 0.67 N for hard wheat glutens and from 0.10 to 0.20 for soft wheat glutens. The recoverable strain was inversely correlated to the maximum force for the hard wheat glutens. However, the recoverable work dropped to < 40% for all of these glutens in the cyclic tensile test, but was positively correlated to the total work of extension. PARTICIPANTS: D. Zhao (1), B. Allvin (2), P. Rayas-Duarte (3), R. Chinnaswamy (4), S. J. MULVANEY (1) (1) Cornell University, Ithaca, NY, USA; (2) Perten Instruments AB, Huddinge, Sweden; (3) Oklahoma State University, Stillwater, OK, USA; (4) USDA GIPSA, Kansas City, MO, USA TARGET AUDIENCES: The target audience are people involved in wheat quality. In particular, exposing them to rheology as a tool for wheat quality. The work is designed to show how rheology is very sensitive to differences in the network structures of wheats with overall good quality. PROJECT MODIFICATIONS: Small deformation rheological measurements did not really differentiate well between soft and hard wheat glutens. It is possible that the mechanism for small deformation elasticity of gluten is different from large scale elasticity. we have shown before that hydrtaed gliadin itself is viscoelastic. Thus, future work will focus on large deformation compressive deformation to make sure we are looking at long range elasticity.
Impacts
These results highlight the important role that elasticity plays in explaining the large deformation rheological properties of gluten. This in turn, may be related to important functional properties such as gluten extensibility and "snap back". Additional testing of ten blended flours indicated that the elastic properties of gluten could be varied in a predictable manner by manipulating the weight percent of the individual cultivars in the blend. Good to excellent bread volume was obtained for several cultivars from this sample set. This suggests that by adjusting the flour blending and optimizing the breadmaking process compensated for the differences in elastic behaviors of these glutens. This work defines those ranges objectively using creep-recovery and tensile testing.
Publications
- No publications reported this period
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: The tensile force at 500% deformation varied by a factor of 5 for 12 hard wheat glutens and a factor of two for 3 soft wheat glutens. The recoverable strain was inversely correlated to the maximum force for the hard wheat glutens. However, not all of the work of extension was recovered in the retraction of the gluten. The tensile test allows for the determination of the relative contribution of elastic forces to the total force during large deformation. This in turn, may be related to important functional properties such as gluten extensibility and "snap back". Results were disseminated at the Annual Meetings of the Institute of Food Technologists and the American Associaton of Cereal Chemists.
PARTICIPANTS: Individuals were S.J. Mulvaney and Dongjun Zhao of Cornell. Partner organizations were Grain Inspection Packers and Stockyard Administration and Perten Instruments. Patricia Rayas-Duarte is a collaborator from Oklahoma State University. Dongjun Zhao is an MS student.
TARGET AUDIENCES: Target Audiences include wheat breeders, grain inspection and classification services, milling industry and flour end-users,
Impacts
The combination of a large rubber-like extensibility and energy loss during extension shows that gluten has properties intermediate between a polymer melt and an elastomeric polymer. This was shown using a combination of small stress creep-recovery and large deformation tensile testing. A single rheological test is needed that captures both aspects of gluten rheological behavior.
Publications
- Zhao, D., Allvin, B., Rayas-Duarte, P., Chinnaswamy, R. and Mulvaney, S. 2007. Separation of plastic and elastic rheological behaviors of gluten and relationship to breadmaking performance. Cereal Foods World Supplement. 52:A72.
- Yeap, P., Mulvaney, S.J. and Rayas-Duarte, P. 2007. Dough extensibility ranges on U.S. wheat cultivars and advanced lines. Cereal Foods World Supplement. 52:A70
- Liang, H., Zhao, D., Allvin, B., Rayas-Duarte, P., Chinnaswamy, R. and Mulvaney, S.J. 2007. Evaluation of methods for separation of plasticity and elasticity in gluten: A step towards possible standard methods. Pages 254-258 in Gluten Proteins 2006. Eds. George L. Lookhart and Perry K.W. Ng. AACC International, Inc. St. Paul, MN.
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Progress 01/01/06 to 12/31/06
Outputs
Work continues on characterization of the viscoelastic properties of gluten. The focus now is on development of a possible standard creep-recovery method to assess the strength and extensibility of wheat gluten in fundamental rheological units. Creep-recovery data is being obtained for glutens from 16 wheat cultivars representing all 6 US wheat classes. In addition, large deformation tensile testing is being used to assess the strength of gluten from these cultivars. Together, these two tests are being designed with recovery cycles to allow separation of viscous and elastic behaviors. Creep-recovery is now preferred over stress relaxation for characterization of the viscoelasticity of wheat gluten.
Impacts
Increased consideration of use of fundamental rheological techniques for assessment of wheat gluten strength and extensibility.
Publications
- Liang, H., Lee, C.C., Rayas-Duarte, P. and Mulvaney, S.J. 2006. Characterization of intercultivar variation on the linear viscoelasatic network properties of wheat gluten II: Effects of temperature and L-Cysteine. Pages 123-136 IN Advances in Biopolymes: Molecules, Clusters, Networks and Interactions. M.L. Fishman, P.X. Qi and L. Wicker (Eds.). ACS Symposium Series 935. American Chemical Society, Washington, DC.
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Progress 01/01/05 to 12/31/05
Outputs
Major work continues in the area of integrating viscoelastic properties of gluten into the broader context of assessment of wheat quality. An article in press in an ACS Symposium series book out this spring (Advances in Biopolymer Systems, Molecules, Clusters and Networks) reports the effects of added L-cysteine and an increase in temperature on the stress relaxation behavior of three glutens with different high molecular weight subunit composition. An increase in temperature up to 40 C decreased the apparent network strength for all of the glutens, but the decrease in viscoelasticity varied between the glutens with different subunit composition. Stronger glutens at 25 C lost more strength with increased temperature than did weaker glutns at 25 C. It was also found that addition of 250 ppm L-cysteine at 25 C to these glutens eliminated most evidence of a network structure in their stress relaxation patterns, even though the protein 'quality' based on HMW glutenin
subunits would remain the same. Thus, it was suggested that the assessment of the rheological 'solid state' quality of wheat should be considered separately from the conventional 'solution' chemistry quality of wheat cultivars. Direct measurement of the viscoelastic properties of gluten eliminate the need to hypothesize how the various solution chemistry wheat fractions may interact in the hydrated state to give rise to viscoelasticity. Also, only certain kinds of rheological measurements can allow for separation of the viscous and elastic components of stresses or strains obtained for gluten.
Impacts
Work is proceeding to develop standard procedures for determining the viscoelastic properties of gluten as part of wheat quality. This includes sample size and geometry, testing conditions, and parameterization of fundamnetal rheological tests.
Publications
- Mulvaney, S. J. 2005. Linear viscoelastic measurements and network structures: General comments and relevance to molecular structures, pp. 219-223. In Chung, O. K. and Lookhart, G. L. (eds.). Third International Wheat Quality Conference, Manhattan, KS. Grain Industry Alliance. Manhattan, KS 66505 (Proceedings)
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Progress 01/01/04 to 12/31/04
Outputs
The effect of moisture content (MC) on the linear viscoelastic properties (LVP) of gliadin hydrated to 30 and 40 percent MC (gliadin(30 percent) and gliadin(40 percent)), respectively) in the terminal zone was determined using frequency-temperature-superposition of the elastic modulus and viscous modulus. These two MC bracketed the equilibrium MC (MCe) of gliadin, which was determined to be 37.6 percent. Smooth master curves were obtained for gliadin (30 percent) and gliadin (40 percent), but the patterns of the master curves for the elastic and viscous moduli, tan delta and the dynamic viscosity for the two gliadin samples were very different than those of poly(dimethylsiloxane) (PDMS), a linear synthetic flexible polymers. These differences were attributed to the dominant effect of non-covalent secondary associations on the LVP of hydrated gliadin in the terminal zone. The energy of activation decreased dramatically for the gliadin 40 percent for temperatures
between about 45 C and 55 C relative to the temperature range 25 C to 45 C and for temperatures between about 55 C up to 70 C relative to the temperature range 25 C to 55 C for gliadin 30 percent. In addition, the master curves for the dynamic moduli for the gliadins showed a power law (PL) dependency on frequency in the terminal zone, which was similar to that of physical and chemical gels near the gel point. Thus, it is concluded that hydrated gliadin cannot be considered to be a simple viscoelastic liquid. Current work involves evaluating the rheological properties of cereal protein fractions (gliadin, low molecular weight glutenin subunits and high molecular weight subunits) and their mixtures.
Impacts
The patterns of the linear viscoelastic functions in the terminal zone of gliadin hydrated to 30 and 40 percent MC suggests that the molecular basis for gliadin viscoelasticity arises from intermolecular, reversible (non-permanent) secondary interactions similar to what is observed for synthetic associating polymers. Master curves for the elastic and viscous moduli indicated that if hydrated gliadin does contain entanglements, they only become evident at frequencies greater than about 1 rad/s at 30 percent MC, and at even higher frequencies for gliadin at 40 percent MC, and so may not be relevant to the slow flow processes involved in the fermentation and oven rise portions of breadmaking. Also, since the linear viscoelastic properties of associating polymers in general do not exhibit the same universal form of linear viscoelasticity in the rubbery plateau and terminal zones as do linear flexible polymers, the linear viscoelastic properties must be determined
separately for each associating polymer of interest, at least until some recognizable pattern emerges for that particular class of associating polymer.
Publications
- Martling, S.E., Mulvaney S.J. and Cohen C. 2004. The Effect of Moisture Content on the Viscoelastic Properties of Hydrated Gliadin. Cereal Chem. 81(2): 207-219.
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Progress 01/01/03 to 12/31/03
Outputs
Recent work has focused more on developing fruit-based functional foods. The goal of this new project is to develop value-added fruit-based snack foods that are rich in natural phytochemicals and have high antioxidant activity from fruit syrups that are by-products of producing dried sweetened fruits. A prototype fruit-jel product has been made from cranberry syrup using modified starch as the gelling agent. It has all natural color, flavor and acidity from cranberries. This prototype will form the basis of developing a class of fruit-based functional foods that maximize nutrition per calories consumed and also pay attention to other nutritional factors such as glycemic index and glycemic load. Biopolymers such as pectin and agar will also be used as gelling agents.
Impacts
The combination of gelatin replacement with other biopolymers, high phytochemical content, natural color, flavor and acidity and higher fiber content could dramatically change the nutritional profile and perhaps the image of gummi-type artificial fruit-based snack products to something more along the lines of dried fruit. However, for the latter the nutritional value can be no better than the starting fruit(except its concentrated), while for the functional food the nutritional profile can be improved. So, "natural" might not always be better, it depends on the objective of the food manufacturer. In our case, the focus will be on developing healthier processed foods that deliver the tastes and textures consumers are used to and have shown they will purchase.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Previously, dispersions of corn starch (CS) and whey protein isolate (WPI) were heated in a RVA-4 at temperatures of 75, 85, and 95 C and pH's of 5, 7,and 9 at total solids contents of 15 and 30 percent. The resultant gels were characterized by their linear viscoelastic properties, large strain mechanical properties and scanning electron microscopy of the dehydrated gels. It was found that mixed gels thermalized at pH 9 showed a compatible starch-WPI network and unusual textural properties. In this work, gels were prepared in the same way at pH 9, but dehydrated to obtain a pregelatinized flour, containing reacted starch and WPI. Doughs were then made form this pregelatinized flour. Doughs containing WPI showed increased stress relaxation and lower DSC melting enthalpies after 7 days of storage at 4 C.
Impacts
This work shows that the interesting and unusual reaction between starch and WPI that occurs during thermalization at pH 9 can be put into a shelf stable dry powder form by dehydration of the resultant gels. This opens up larger possibilities for applications of the starch-whey protein biopolymer, particularly in starch-based foods.
Publications
- Shim, J. and Mulvaney, S. J. 2002. Effects of Pregelatinization Conditions and Added Whey Protein Isolate on Corn Starch Dough Properties. Cereal Foods World. 47(9):440-446.
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Progress 01/01/01 to 12/31/01
Outputs
Dispersions of corn starch (CS) and whey protein isolate (WPI) were heated in a RVA-4 at temperatures of 75, 85, and 95 C and pH's of 5, 7, and 9 at total solids contents of 15 and 30%. The resultant gels were characterized by their linear viscoelastic properties, large strain mechanical properties and scanning electron microscopy of the dehydrated gels. Surprisingly, WPI gels showed extensive stress relaxation (SR) indicative of a viscoelastic liquid , even though these gels are often considered elastic based on small amplitude oscillatory testing. On the other hand, CS gels relaxed very little in 2,000 s. Based on SR results and SEM, WPI/CS mixed gels with 25% and 50% CS formed unique compatible network structures under some conditions of temperature and pH. The corresponding gels combined the elasticity of CS and the internal stress dissipation of WPI. This in turn led to unusual synergies in the fracture stress and strain of these mixed gels not seen before.
Additional work has been started with gelatin/corn syrup/sugar systems as a model for non-chocolate confectionery foods. See NYC-143332 for progress report related to cereals.
Impacts
Possible new uses for whey proteins as gelling agents in confectionery and snack food products. Potential for replacing gelatin. Control of gel properties via control of process conditions rather than chemical additives.
Publications
- Shim J. and Mulvaney, S.J. 2001. Effect of heating temperature, pH, concentration, and starch/whey-protein ratio on the viscoelastic properties of corn starch/whey protein mixed gels. J. Sci. Food and Agriculture. 81:1-12.
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