Progress 10/01/04 to 09/30/10
Outputs
OUTPUTS: Results from research conducted under this project the subject of over 30 submitted scientific presentations and 26 keynoted/invited presentations. Some key presentations are listed below: National Foegeding, E.A. 2005. Chemistry and Functionality of Whey Proteins. Food Chemistry Divisional Lecture, Annual Meeting of the Institute of Food Technologists, New Orleans, LA. Foegeding, E.A. 2005. Factors Determining Flavor and Stability of Acidic Whey Protein Beverages. 4th International Whey Conference, Chicago, IL. Foegeding, E.A. 2006. Chemistry and Functionality of Whey Proteins. 20th J. R. Brunner Protein Symposium, Michigan State University, East Lansing, Michigan. Foegeding, E.A. 2007. Expanding the Functionality of Whey Ingredients in Beverages and Foods. DMI Innovation Symposium, Scottsdale, AZ. Foegeding, E.A. 2008. Opportunities and Challenges with Whey Protein Beverages. Invited Speaker. Dairy Ingredient Symposium, March 18-19, San Francisco, CA. Foegeding, E.A. 2009. Design of successful performing interfaces: Examples in foams and cheese. Food Structure and Functionality Forum, 100th AOCS Annual Meeting and Expo. Orlando, FL. Foegeding, E.A. 2010. Maximizing the functional properties of dairy proteins in beverages applications. 12th Annual Dairy Ingredient Symposium, March 2-3, San Francisco, CA. International Foegeding, E.A. 2004. Factors Determining the Physical Properties of Protein Foams. Invited keynote speaker, 7th International Hydrocolloids Conference, Melbourne, Australia. Foegeding, E.A. 2005. Protein Responses to High Heat Treatment. World Dairy Summit, Vancouver, Canada. Foegeding, E.A., Vardhanabhuti, B. and Yong, Y.H. 2008. Controlling protein aggregation through interactions with polysaccharides and chaperone proteins. Invited Keynote Speaker. International Hydrocolloids Conference, Singapore. Foegeding, E.A. and Daubert, C.R. 2008. Sensory texture based on rheological properties: Applications in model foods and cheese. Invited Keynote Speaker, 16th Nordic Rheology Conference, Copenhagen, Denmark. Foegeding, E.A. 2008. Impact of protein modification: Designed functionalities as food ingredients. Invited Speaker, 5th International Whey Conference, Paris, France. Foegeding, E.A. 2009. Using dairy ingredients to alter the texture of foods. 6th NIZO Dairy Conference. Dairy Ingredients: Innovations in Functionality. Papendal, the Netherlands. Industry Foegeding, E.A. 2004. Whey Protein-Containing Beverages: Factors determining Stability and Flavor. PepsiCo, New York. Foegeding, E.A. 2007. From Acrylamide Gels to Cheese. Kraft Foods, Chicago, IL. Foegeding, E.A. 2007. From Acrylamide Gels to Cheese. NIZO, The Netherlands. Foegeding, E.A. 2007. Whey Protein And Egg White Foams: The function of sugar and copper. 50th Thematic Meeting, DMV International, The Netherlands. PARTICIPANTS: E. Allen Foegeding (PI) and Paige Luck. Ms. Luck is a research specialist who has conducted experiments. TARGET AUDIENCES: Food processors and manufacturers of whey protein ingredients. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
One of the main functional properties of whey proteins is heat stability - the resistance to form phase-separated aggregates after a thermal process. The heat stability of beta-lactoglobulin was investigated regarding stabilizing effects of dextran sulfate and destabilizing effects of NaCl. At pH values between 5.6 and 6.0, beta-lactoglobulin interacts with dextran sulfate and increases heat stability. Each pH value has an optimum ratio of dextran sulfate to beta-lactoglobulin where aggregation is inhibited. As the molecular weight of dextran sulfate increases, the concentration range that decreases aggregation narrows. These data can be explained by two mechanisms. When solution pH is between 5.8 and 6.0, there is an interaction between native beta-lactoglobulin and dextran sulfate that alters the denaturation and aggregation process such that smaller aggregates are formed. Polymer-polymer phase incompatibility occurs at higher polymer concentrations and this mechanism is increased as the molecular weight of the dextran sulfate polymer increases. Another approach to increase whey protein thermal stability is by using caseins as molecular chaperones to alter the aggregation process of unfolded whey proteins. We examined the effect of beta- and alpha-casein on the thermal denaturation and aggregation of beta-lactoglobulin and alpha-lactalbumin. Beta-casein is able to inhibit the aggregation of beta-lactoglobulin and alpha-lactalbumin at temperatures between 60 and 90 C. In contrast, alpha-casein is only effective up to 70 to 75 C. The presence of caseins does not alter denaturation of beta-lactoglobulin; thermal stability increases by altering the size and shape of the aggregates. A second investigation looked at the chaperone-effect over a wider range of solvent conditions and temperatures above 100 C. The ability of beta-casein to alter the aggregation of whey proteins is observed at temperatures up to 145 C, validating this approach for use in whey protein beverages manufactured at neutral pH by aseptic processing. The chaperone effect is lost when electrostatic conditions do not favor inter-protein electrostatic repulsion. The casein chaperone mechanism appears to be providing an alternative path for aggregation. This research demonstrates a new, unique way to alter protein functionality without chemically modifying proteins. Another functional property of whey proteins is foam formation and stabilization. Foaming properties of whey protein isolate and egg white were evaluated to determine if physical chemical models could account for differences in foam stability and rheology (yield stress). Foam drainage rate was explained for both proteins by changes in average bubble size, suggesting that disproportionation and coalescence were coupled with drainage rate. A combination of continuous phase viscosity and interfacial elasticity formed a master curve explaining foam drainage rate. In contrast, foam yield stress could not be explained by physical parameters alone (interfacial elasticity, bubble size and bubble phase volume); suggesting that there are protein-specific effects.
Publications
- Yang, X., and Foegeding, E.A. 2010. Effects of sucrose on egg white protein and whey protein isolate foams: factors determining properties of wet and dry foams (cakes). Food Hydrocolloids 24:227-238.
- Vardhanabhuti, B., Kayankarn, W., and Foegeding, E.A. 2010. Formation of elastic whey protein gels at low pH by acid equilibration. J. Food Science 75:E305-E313.
- Rogers, N.R., McMahon, D.J., Daubert, C.R., Berry, T.K. and Foegeding, E.A. 2010. Rheological properties and microstructure of Cheddar cheese made with different fat contents. Journal of Dairy Science 93:4565-4576.
- Vardhanabhuti, B. and Foegeding, E. A. 2010. Evidence of interactions between whey proteins and mucin: their implication on the astringency mechanism of whey proteins at low pH. In Gums and Stabilisers for the Food Industry 15. P.A. Williams and Glyn O. Phillips editors, pp. 137-146
- Foegeding, E. A., Vardhanabhuti, B., and Luck, P.J. 2010. Whey protein products. In Encyclopedia of Dairy Sciences, 2nd edition, J. W. Fuquay, P. F. Fox, and P. L. H. McSweeney (eds.). New York: Academic Press.
- Foegeding, E.A., Vardhanabhuti, B., and Yang, X. 2010. Dairy Systems. In Practical Food Rheology-An interpretive approach, Norton, I.T, Spyropoulos, F. and Cox, P. (eds). Wiley.
- Kelly, M., Vardhanabhuti, B., Luck, P., Drake, M.A., Osborne, J., and Foegeding, E.A. 2010. Role of protein concentration and protein-saliva interactions in the astringency of whey proteins at low pH. J. Dairy Science 93:1900-1909.
- Leksrisompong, P. Barbano, D.M., Foegeding, E.A., Gerard, P.D. and Drake, M.A. 2010. The roles of fat and pH on the detection thresholds and partition coefficients of three compounds: diacetyl, -decalactone, and furaneol. J. Sensory Studies 25:347-370.
- Barden, L., Cakir, E., Leksrisompong, P.N., Ryan, K.N., Foegeding, E.A. and Drake, M.A. 2010. Effect of flavor on perceived texture of whey protein isolate gels. J. Sensory Studies 25:447-462.
- Vardhanabhuti, B., Kelly, M., Luck, P., Drake, M.A., and Foegeding. E.A. 2010. Roles of charge interactions on astringency of whey proteins at low pH. Journal of Dairy Science 93:1890-1899.
- Yong, Y.H. and Foegeding, E.A. 2010. Caseins: Utilizing molecular chaperone properties to control protein aggregation in foods. J. Agricultural and Food Chemistry 58, 685-693.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Results from research conducted under this project were presented at the following events: Foegeding, E.A. 2009. Linking mechanical and sensory aspects of texture: Advances and challenges. Presented at the international symposium on Rheology and Fracture to honor Dr. Ton van Vliet on his retirement. Wageningen, the Netherlands. Foegeding, E.A. 2009. Using dairy ingredients to alter the texture of foods. 6th NIZO Dairy Conference. Dairy Ingredients: Innovations in Functionality. Papendal, the Netherlands. Foegeding, E.A. 2009. Design of successful performing interfaces: Examples in foams and cheese. Food Structure and Functionality Forum, 100th AOCS Annual Meeting and Expo. Orlando, FL. PARTICIPANTS: E. Allen Foegeding (PI) and Paige Luck. Ms. Luck is a research specialist who has conducted experiments. TARGET AUDIENCES: Food processors and manufacturers of whey protein ingredients. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
We have previously established that the so-called molecular chaperone properties of caseins can be used to control aggregation of beta-lactoglobulin and alpha-lactalbumin. This was established under restricted conditions of pH, ionic strength and temperature. The investigation was extended to solvent conditions that were less favorable for electrostatic repulsion among proteins and temperatures above 100 C. The ability of beta-casein to alter the aggregation of whey proteins, as seen by a decrease in turbidity and aggregate size, is observed at temperatures up to 145 C, validating this approach for use in whey protein beverages manufactured at neutral pH by aseptic processing. The chaperone effect is lost when electrostatic conditions do not favor inter-protein repulsion (i.e., pH approaching isoelectric point increased solvent ionic strength). Differential scanning calorimetry results showed that the presence of caseins did not alter the denaturation process and the kinetics of loss of native whey proteins was not changed or slightly increased in the presence of beta-casein. The casein chaperone mechanism appears to be providing an alternative path for aggregation. When electrostatic repulsion is low, whey proteins form intra-protein aggregates in preference to aggregating with beta-casein. Alternatively, with sufficient electrostatic repulsion, beta-casein interacts with denatured whey proteins and this aggregation pathway produces smaller aggregates. We have established that beta-casein has the potential to improve clarity and stability in protein-containing beverages made at near-neutral pH requiring thermal processing at temperatures above 100 C. This research demonstrates a new, unique way to alter protein functionality without chemically modifying proteins. Foaming properties of whey protein isolate and egg white were evaluated to determine if physical chemical models could account for differences in foam stability and rheology (yield stress). Foam drainage rate was explained for both proteins by changes in average bubble size, suggesting that disproportionation and coalescence were coupled with drainage rate. A combination of continuous phase viscosity (related to drainage) and interfacial elasticity (related to disproportionation) formed a master curve explaining foam drainage rate. In contrast, foam yield stress could not be explained by physical parameters alone (interfacial elasticity, bubble size and bubble phase volume); suggesting that there are protein-specific effects. While the nature of these effects was not determined, it was postulated that interactions of the proteins in the continuous phase may be involved.
Publications
- Vardhanabhuti, B, Yucel, U., Coupland, J.N., and Foegeding, E.A. 2009. Interactions between β-lactoglobulin and dextran sulfate at near neutral pH and their effect on thermal stability. Food Hydrocolloids 23:1511-1520. Harrington, J.C., Foegeding, E.A., Mulvihill, D.M. and Morris, E.R. 2009. Segregative interactions and competitive binding of Ca2+ in gelling mixtures of whey protein isolate with Na+ kappa-carrageenan. Food Hydrocolloids 23:468-489.
- Mudgal, P., Daubert, C.R. and Foegeding, E.A. 2009. Cold-set thickening mechanism of beta-lactoglobulin at low pH: Concentration effects. Food Hydrocolloids 23:1762-1770.
- Yang, X., Berry, T.K. and Foegeding, E.A. 2009. Foams prepared from whey protein isolate and egg white protein: 1. Physical, microstructural and interfacial properties. J. Food Science 74:E259-E268.
- Berry, T.K. Yang, X. and Foegeding, E.A. 2009. Foams prepared from whey protein isolate and egg white protein: 2. Changes associated with angel food cake functionality. J. Food Science 74:E269-E227
- Rogers, N.R., Drake, M.A., Daubert, C.R., McMahon, D.J., Bletsch, T.K. and Foegeding, E.A. 2009. The effect of aging on low, reduced and full fat Cheddar cheese texture. J. Dairy Sci. 92:4756-4772.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Results from research conducted under this project were presented at the following events: Foegeding, E.A. 2008. Opportunities and Challenges with Whey Protein Beverages. Invited Speaker. Dairy Ingredient Symposium, March 18-19, San Francisco, CA. Foegeding, E.A., Vardhanabhuti, B. and Yong, Y.H. 2008. Controlling protein aggregation through interactions with polysaccharides and chaperone proteins. Invited Keynote Speaker. International Hydrocolloids Conference, Singapore. Foegeding, E.A. 2008. Impact of protein modification: Designed functionalities as food ingredients. Invited Speaker, 5th International Whey Conference, Paris, France. PARTICIPANTS: E. Allen Foegeding (PI) and Paige Luck. Ms. Luck is a research specialist who has conducted experiments. TARGET AUDIENCES: Food processors and manufacturers of whey protein ingredients. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Recent investigations have implicated caseins as being molecular chaperones in that they can alter the aggregation process of unfolded proteins. This biological function could be very important to food applications where excessive protein aggregation is considered a detriment to quality, such as in protein-fortified beverages. Previous investigations were conducted under very dilute solutions conditions (generally 1% w/w protein or less), which are far from the concentrations observed in many food applications (3 - 10% w/w protein); therefore, we examined the effect of beta- and alpha-casein on the thermal denaturation and aggregation of beta-lactoglobulin and alpha-lactalbumin at higher concentrations and over a broader range of temperatures. Beta-casein was able to inhibit the aggregation of beta-lactoglobulin and alpha-lactalbumin at temperatures between 60 and 90 C as shown by a dramatic decrease in turbidity. In contrast, alpha-casein was only effective up to 70 to 75 C. Differential scanning calorimetry results showed that the presence of caseins did not alter the denaturation process of beta-lactoglobulin. Likewise, the rate of loss of soluble monomer/dimer beta-lactoglobulin could not explain the difference in turbidity. Analysis of heat-induced aggregates by static light scattering showed that the caseins were altering the size and shape of the aggregates. Interestingly, this was similar to what has been previously observed in our laboratory regarding the effect of dextran sulfate on heat-induced aggregation. Based on these results, it appears that beta- and alpha-casein are altering the thermal stability of proteins by steering the aggregation process such that aggregate size and diameter are decreased. This has implications to beverage applications, where a low degree of turbidity is desired, and to gelation, where altering the aggregation process will produce different gel network structures. Therefore, caseins have the potential to improve clarity in protein-containing beverages and to direct gel network formation thereby altering molecular entrapping, textural and water-binding properties. This research demonstrated a new, unique way to alter protein functionality. It suggests that protein aggregation can be controlled by the proper mix of proteins. This has implications to stability of proteins in beverages; utilization of protein nano- or micro-gel particles for encapsulation; and to designing specific textures in foods.
Publications
- Vardhanabhuti, B. and Foegeding, E. A. 2008. Effects of dextran sulfate, NaCl, and initial protein concentration on thermal stability of beta-lactoglobulin and alpha-lactalbumin at neutral pH. Food Hydrocolloids: 22:752-762.
- Luck, P.J. and Foegeding, E.A. 2008. The role of copper in protein foams. Food Biophysics 3:255-260.
- Beecher, J.W., Drake, M.A., Luck, P.J. and Foegeding, E.A. 2008. Factors regulating astringency of whey protein beverages. Journal of Dairy Science 91:2553-2560.
- Zhang, J., Daubert, C.R., Mulligan, J. and Foegeding, E.A. 2008. Additive effect on the rheological behavior of alginate gels. J. Texture Studies 39:582-603.
- Yong, Y.H. and Foegeding, E.A. 2008. Effects of caseins on thermal stability of bovine beta-lactoglobulin. J. Agric. Food Chem. 56:10352-10358.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: The effect of dextran sulfate (ranging in molecular weight from 5,000 to 500,000 Da) on the heat stability of pH 5.6 to 6.2 beta-lactoglobulin solutions was investigated. At pH values between 5.6 and 6.0, beta-lactoglobulin interacted with dextran sulfate as demonstrated by the development of large soluble aggregates and alteration in denaturation temperature and enthalpy. When heated at 85 C for 15 min, each pH value showed an optimum ratio of dextran sulfate to beta-lactoglobulin where aggregation was inhibited, with lower pH requiring higher amounts of dextran sulfate. Increasing dextran sulfate above the optimal ratio caused an increase in aggregation. As the molecular weight of dextran sulfate increased, the concentration range that decreased aggregation narrowed. These data can be explained by two mechanisms. When solution pH is between 5.8 and 6.0, there is an interaction between native beta-lactoglobulin and dextran sulfate. This interaction alters the denaturation
and aggregation process such that smaller aggregates are formed. The interaction is due to electrostatic attraction, as adding 30 mM NaCl contributes enough counter ions that the interaction is prevented and aggregation is not altered. Polymer-polymer phase incompatibility occurs at higher polymer concentrations and this mechanism is increased as the molecular weight of the dextran sulfate polymer is increased. Overall, this suggests that an optimum of pH, polymer concentration and polymer size exists where association between beta-lactoglobulin and dextran sulfate inhibits heat-induced aggregation. The contribution of microstructure to yield stress and heat stability of whey protein isolate and egg white foams was also investigated. Foam structure was determined using confocal microscopy. Egg white foams had smaller, more numerous bubbles that showed greater stability over time compared to whey protein isolate foams. A linear correlation was observed between foam yield stress and the
product of bubble count/area and surface tension of the foaming solution. This supports existing models that predict that yield stress is related to the surface tension and total surface area. Once heated, egg white foams showed signs of network formation at 45 C, while whey protein isolate foams continued to expand at temperatures higher than 55 C. Moreover, when comparing foam expansion in batters (foam plus flour and sugar), whey protein isolate foams had large bubbles indicating rapid destabilization, while egg white foams formed a uniform structure of small bubbles that maintained their integrity up to 85 C. These data clearly show that egg white foams set into a network structure around 45 C and this structure helps maintain stability upon further heating. A similar transition was not observed with foams made from whey protein isolate.
PARTICIPANTS: E. Allen Foegeding - PI Paige Luck - Research analysist Tristan Berry - Graduate Student Xin Yang - Graduate Student
TARGET AUDIENCES: People using food proteins to improve the quality of existing products and develop new products.
Impacts
This research demonstrated to key factors regarding protein functionality. First, the ability of charged polysaccharides to inhibit heat-induced protein aggregation depends on a limited interaction of native molecules. The precise conditions for this interaction will depend on the protein charge, as influence by pH, and the molecular size of the protein and polysaccharide. In a different application, protein foams, low temperature thermal transitions of the foam structure appear to be essential for overall baking stability.
Publications
- Rosell, C.M. and Foegeding, E.A. 2007. Interaction of hydroxypropylmethylcellulose with gluten proteins: Small deformation properties during thermal treatment. Food Hydrocolloids 21:1092-1100.
- Zhang, J., Daubert, C.R. and Foegeding, E.A. 2007. A proposed strain-hardening mechanism for alginate gels. Journal of Food Engineering 80:157-165.
- Davis, J.P. and Foegeding, E.A. 2007. Comparisons of the foaming and interfacial properties of whey protein isolate and egg white proteins. Colloids and Surfaces B: Biointerfaces 54:200-210.
- Foegeding, E.A. and Drake, M.A. 2007. Sensory and mechanical properties of cheese texture. J. Dairy Science 90:1611-1624
- Childs, J.L., Foegeding, E.A., Daubert, C.R. and Stefanski, L 2007. Factors regulating shreddability of cheese. J. Dairy Science 90:2163-2174.
- McGuffey, M.K., Otter, D.E., van Zanten, J.H. and Foegeding, E.A. 2007. Aggregation of alpha-lactalbumin isolate in a neutral pH nutritional beverage mineral salt environment. International Dairy Journal 17:1168-1178.
- Carunchia Whetstine, M.E. Luck, P.J., Drake, M.A., Foegeding, E.A., Gerard, P.D. and Barbano, D.M. 2007. Characterization of Flavor and Texture Development within 291 kg Blocks of Milled and Stirred Curd Cheddar Cheese. J. Dairy Science 90:3091-3109.
- Foegeding, E.A. 2007. Rheology and sensory texture of biopolymer gels. Current Opinion in Colloid and Interface Science 12:242-250.
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Progress 10/01/05 to 09/30/06
Outputs
The heat stability of beta-lactoglobulin was investigated as it relates to making whey protein-containing beverages. The effect of dextran sulfate, NaCl and initial protein concentration on the loss of native dimers and the molecular weight of aggregates formed during heating were studied. Heating beta-lactoglobulin (3-6%, 0 or 60 mM NaCl and 0-0.1 dextran sulfate/protein ratio, pH 7.0) at 85oC for 15 min resulted in the loss of more than 94% of the dimers. The soluble aggregates resulting from heating were studied using a multi-angle laser light scattering detector. Heated beta-lactoglobulin samples (3-6% protein) without the addition of NaCl remain soluble after heating and centrifugation. However, heating in the presence of 60 mM NaCl caused a major loss in solubility. Dextran sulfate, at the proper level, increased the stability of heated beta-lactoglobulin in the presence of 60 mM NaCl by decreasing the average aggregate molecular weight. The interaction between
-lactoglobulin and dextran sulfate in the presence of 60 mM NaCl was studied. After heat treatment, samples were centrifuged and the amount of soluble hexose was determined to indicate the amount of soluble dextran sulfate. When dextran sulfate was present at 0.01:1 w/w ratio with beta-lactoglobulin, there was an increase in the amount of soluble dextran sulfate. This increase in soluble dextran sulfate coincided with the increase in soluble protein (from 30.9 to 45.4%), suggesting that there was an interaction between beta-lactoglobulin and dextran sulfate. At high ratios of dextran sulfate to protein there was phase separation. It was concluded that, when combined at the proper ratio with beta lactoglobulin, dextran sulfate aids heat stability by reducing aggregate size. In another investigation, a trained sensory panel evaluated the viscosity and pH effects on astringency of whey protein-fortified model drinks. Increasing viscosity (1.6 mPa s - 7.7 mPa s) did not reduce
astringency, however there were significant differences across the pH range investigated (pH 2.6 - 6.8). Acidic drinks were higher in astringency and sourness compared to the drink at neutral pH. Changes in optical density of saliva and drink mixtures before and after centrifugation were investigated in an attempt to correlate aggregation and precipitation with astringency. Saliva and drink mixtures showed that aggregation and precipitation was taking place, and the degree of precipitation correlated with perceived astringency. The data suggests that electrostatic interactions between positively charged whey proteins at low pH and saliva proteins with low isoelectric points are responsible for aggregation and precipitation, resulting in the perception of astringency.
Impacts
This research shows two important facts relative to making beverages containing whey proteins. First, when making beverages at neutral pH, certain polysaccharides may help by preventing too much aggregation. Second, the astringency of whey protein drinks is highly dependent on pH.
Publications
- Foegeding, E.A., Luck, P.J. and Davis, J.P. 2006. Factors determining the physical properties of protein foams. Food Hydrocolloids 20:284-292.
- Barrangou, L.M, Daubert, C.R. and Foegeding, E.A. 2006. Textural properties of agarose gels. I. Rheological and fracture properties. Food Hydrocolloids 20:184-195.
- Barrangou, L.M, Daubert, C.R. and Foegeding, E.A. 2006. Textural properties of agarose gels. II. Relationship between fracture properties, small-strain rheology, and sensory texture. Food Hydrocolloids 20:196-203.
- Foegeding, E.A. 2006. Food biophysics of protein gels: a challenge of nano and macroscopic proportions. Food Biophysics 1:41-50.
- Zhang, J. Daubert, C.R. and Foegeding, E.A. 2006. Polyacrylamide gels as elastic models for food gels: Fracture properties affected by dextran and glycerol. J. Texture Studies 37:200-220.
- Barrangou, L.M., Drake, M.A., Daubert, C.R. and Foegeding, E.A. 2006. Sensory texture related to large-strain rheological properties of agar/glycerol gels as a model food. Journal of Texture Studies 37:241-262.
- Zhang, J., Daubert, C.R. and Foegeding, E.A. 2007. A proposed strain-hardening mechanism for alginate gels. Journal of Food Engineering 80:157-165.
- Hamann, D.D., Zhang, J., Daubert, C.R., Foegeding, E.A.,Diehl K.C. 2006. Analysis of compression, tension and torsion for testing food gel fracture properties. Journal of Texture Studies 37:620-639.
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Progress 10/01/04 to 09/30/05
Outputs
The foaming properties of egg white, a modified egg white (sodium laurel sulfate added) and whey protein isolated were compared in the presence and absence of sucrose. All three protein ingredients produced foams with similar overrun, which is consistent with previous findings. In contrast, egg white protein foams were stronger (higher yield stress) and more stable (longer half life) than whey protein isolate foams. Moreover, addition of sucrose to foaming solutions increased yield stress of egg white foams, while it decreased the yield stress of whey protein isolate foams. One possible reason for the differences could be in the interfacial properties. Without sucrose, egg white decreases surface tension at a much faster rate than whey protein isolate. Addition of sucrose to the foaming solutions caused an increase in surface tension; however, egg white and whey protein isolate were similarly affected. More information was obtained by determining the viscoelastic
properties of the interface. The dilatational interfacial elasticity was measured in the presence and absence of sucrose. As was observed for the bulk property of yield stress, the addition of sucrose alters the properties of the protein-air interface. As sucrose concentration was increased, the interfacial film elasticity decreased for whey protein isolate, and increased for egg white. This is also seen in the phase angle data, where increasing sucrose concentration made whey protein isolate films more viscous, and egg white films more elastic. The data for egg white showed a clear correlation between increased foam yield stress and increased interfacial elasticity. In other words, a strong interface makes for a strong foam. Adding sucrose increased interfacial elasticity and foam yield stress. The opposite results were seen for whey protein isolate. Adding sucrose decreased yield stress and interfacial elasticity. These results clearly demonstrate that one of the major differences
between egg white and whey proteins is the way they interact with sucrose. This is, to the best of our knowledge, the first data showing a clear difference between egg white and whey proteins on how sucrose alters foaming properties. This is significant because sugar is included in the foaming solution for many food products, such as angel food cakes and various confections.
Impacts
Our results clearly show that adding sucrose to egg white foaming solutions causes an increase in interfacial elasticity and foam yield stress. In contrast, sucrose causes a decrease in whey protein isolate interfacial elasticity and foam yield stress. These observations strongly suggest that one way to improve the functional properties of whey proteins is to make them more compatible with sucrose.
Publications
- Doucet, D. and Foegeding, E.A. 2005. Gel formation of peptides produced by extensive enzymatic hydrolysis of beta-lactoglobulin. Biomacromolecules 6:1140-1148.
- McGuffey, M.K., Epting, K.L., Kelly, R.M. and Foegeding, E.A. 2005. Denaturation and aggregation of three alpha-lactalbumin preparations at neutral pH. J. Agric. Food Chem. 53:3182-3190.
- Davis, J.P., Doucet, D. and Foegeding, E.A. 2005. Foaming and interfacial properties of hydrolyzed beta-lactoglobulin. Journal of Colloid and Interface Science 288:412-422.
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