Whey Research Sponsored by CDRF

Establishing Uniqueness of Dairy Proteins Against Competitive Soy Protein Products*

MaryAnne Drake, North Carolina State University, Raleigh, NC
Allen Foegeding, North Carolina State University, Raleigh, NC

Project Objectives

1. Identify and compare descriptive sensory properties of whey protein products to soy protein products

2. Compare functional properties of whey and soy protein products

Tremendous flavor variability was observed among whey and soy proteins indicating that flavor varies widely among different suppliers for each product. Additionally, different sensory attributes distinguished whey proteins from soy proteins. Whey proteins were primarily characterized by cardboard, brothy, and soapy flavors while the three primary flavors observed in soy proteins were flour, roasted, and cereal. These results indicate that soy and whey proteins have distinctive flavor differences.

Most participants purchased granola bars (69%) and cereal bars (47%) versus sports/nutritional bars (29%). Forty-nine percent of participants did not consume protein bars and/or meal replacement bars. However, 24% of consumers stated that they consumed protein bars at least once per month. Fifty-three percent of the consumers felt they had a moderate level of knowledge about the use and function of protein in foods. The majority of the consumers polled (68%) did not purchase food and/or beverages with added protein. Instead, dairy products (61%) and meat products (69%) were most likely to be consumed and purchased if choosing a product high in protein.

Key health claims that positively influenced consumers were “develops and maintains healthy bones”, “decreases chances of heart disease”, “decreases cancer risk”, “increases mental alertness”, and “prevents tooth decay” . Weight control, immune system enhancement, development of lean muscle mass, and appetite reduction were not as important as these other health claims. Of the 147 consumers polled, the results indicated that consumer knowledge of health benefits and product claims of soy products centered on the high protein value of soy-based foods and/or beverages (65%). Fifty-eight percent indicated that products with soy protein were low fat/fat-free and forty-five percent indicated that soy products were cholesterol free. In contrast, consumer perception of health benefits and product claims of dairy products were that they provide/develop and maintain healthy bones (88%) and contain calcium (80%). Sixty-three percent of the consumers agreed that dairy products have a great taste. The majority of the consumers polled indicated that “cow’s milk is a healthy food” (85% strongly agree and agree) and that “soy milk is a healthy food” (70% strongly agree and agree). Eighty-four percent (strongly agree and agree) of the consumers polled felt “cow’s milk tastes good”. However, for the statement “soy milk tastes good”, eighty-two percent of the consumers strongly disagreed, disagreed, or did not know if soy milk tastes good.

Soy proteins were much less soluble in water and exhibited significantly higher turbidity readings as compared to whey proteins. The protein solubility of WPI and WPC80 solutions was ~38 mg/mL and ~34 mg/mL, respectively. SPI solubility was variable (12-28 mg/mL) while SPC solutions exhibited more uniformity (~25 mg/mL). Electrophoretic analyses revealed several unique differences among WPI protein banding patterns. Protein banding patterns for WPC80, SPI, and SPC70 were consistent within each prototype vs. protein type, respectively. Heat stability studies indicated that each commercial powder exhibited unique properties that were likely determined by the specific manufacturing process under which it was made. In general, WPI solutions were more sensitive to heat denaturation than WPC solutions over the entire testing range, 70°C-90°C. SPI and SPC solutions, prepared in 100 mM NaCl, pH 7.0, were much more likely to precipitate especially at higher temperatures. Color analyses revealed that the WPI powders were the lightest, followed in most cases by SPI>WPC>SPC. Color variability was greatest among the WPC powders. Data analysis for functional properties is still underway.

The significance and industry benefit from this work
Soy protein products are currently very competitive with whey protein products. The proposed research will provide side-by-side comparisons of flavor and functional properties of whey and soy proteins. This information will provide crucial knowledge for strategic and competitive marketing, promotion, and positioning of whey proteins and whey protein products.

Conclusions
Both whey and soy proteins exhibit flavor, and specific flavors are associated with each type of protein. Additionally, each protein type exhibits different functional properties, but there is also significant variability within each protein type. Consumers perceived soy and dairy products as healthy foods, but different health benefits were associated with each product. Further, dairy products were generally perceived as better tasting than soy products.


Bioactive Compound Incorporation in Protein Films
and Coatings*

John M. Krochta, UC Davis

Project Objectives
The overall objective of this project is to apply the whey protein film and coating concept to the commercial opportunity of food protection by incorporation of bioactive compounds to increase the safety and quality of food systems. The specific objectives are 1) to increase microbial food safety of foods by inhibiting Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica using whey protein edible films and coatings incorporating lactoferrin, lactoperoxidase systems, and lysozyme and 2) extend the chemical shelf life of foods by inhibiting lipid oxidation using whey protein edible coatings incorporating natural a-tocopherol and/or ascorbyl palmitate.

Progress
Lysozyme (LZ) inhibited the pathogen L. monocytogenes and the lactoperoxidase system (LPOS) inhibited the pathogens L. monocytogenes, S. enterica, and E. coli O157:H7, in both broth and on agar microbial media. However, lactoferrin (LF) did not exhibit antimicrobial activity against these pathogens.

LZ and LPOS, which showed the antimicrobial activity, were incorporated into whey protein isolate (WPI)-based films and coatings, and the antimicrobial activity of the films and coatings were studied. WPI films incorporating LZ inhibited the growth of L. monocytogenes and WPI films incorporating LPOS completely inhibited S. enterica and E. coli O157:H7 on an agar medium.

Incorporation of LZ in WPI films increased film stiffness and decreased film stretchability and oxygen permeability (OP), but did not significantly alter film strength and color. Incorporation of LPOS at low levels did not affect these film properties. High levels of LPOS reduced film stiffness and strength, but had no effect on film color and reduced the OP. Overall, the presence of the LZ and LPOS antimicrobials in WPI films and coatings did not affect film mechanical, barrier or visual properties sufficiently to influence their usefulness.

WPI coatings prepared with LZ inactivated L. monocytogenes, total aerobes and yeasts/molds on smoked salmon samples. WPI coatings prepared with LPOS inactivated L. monocytogenes on smoked salmon and S. enterica and E. coli O157:H7 on roasted turkey. WPI coatings prepared with LZ and LPOS retarded growth of L. monocytogenes at both 4 and 10°C. Significant inhibitions of the growth of S. enterica and E. coli O157:H7 were observed in coated roasted turkey stored at both 4 and 10°C.

LPOS-incoporated WPI film coatings were more effective than spreading water-based LPOS solutions on roasted turkey to inhibit the growth of S. enterica and E. coli O157:H7. The antimicrobial activity of the coatings with LZ and LPOS was more noticeable when coating was applied before inoculation with the pathogens than when coating was applied after inoculation. Whey protein coatings incorporating LZ and LPOS inhibited not only L. monocytogenes, S. enterica, and E. coli O157:H7, but also total aerobic microorganisms including molds. Thus, microbial safety and stability of smoked salmon and roasted turkey were significantly improved by inhibiting the pathogens and endogenous aerobic microorganisms, using WPI coatings incorporating LZ and LPOS systems.

Two methods of incorporating ascorbyl palmitate or tocopherol antioxdant into WPI film-forming solutions were developed. One method introduces the antioxidants as dry powders. The other method solubilizes the antioxidants in ethanol before adding to the WPI solution.
The method of antioxidant incorporation had no significant difference on viscosity of WPI film-forming solutions. There was a small effect on WPI film-forming solution turbidity. However, the mixing methods did not produce any difference in the film transparency or oxygen permeability. The antioxidant-incorporated WPI film transparencies and oxygen permeabilities were not different from the control WPI film without any antioxidants. Thus, incorporation of antioxidants
in WPI films and coatings will have no detrimental effects.

Significance and industry benefit
The large production of whey in the U.S., particularly in California, has made identifying uses for whey proteins an important goal of the dairy industry. The concept of whey protein films and coatings incorporating bioactive compounds, a specific whey application developed by this research, has potential for providing a significant opportunity for whey processors. Demonstration of the effectiveness of the concept in this research can lead to high-value commercial use of whey protein. Achievement of the objective will generate significant new uses of whey protein as the concept of bioactive-incorporated whey protein films and coatings is applied to improve existing food products and develop new food products.

Conclusions
Incorporating the milk-derived antimicrobial compounds lysozyme (LZ) and lactoperoxidase (LPOS) in whey protein isolate (WPI) films and coatings is more effective than direct application of these antimicrobials to food surfaces. By inhibiting the diffusion of antimicrobial away from the food surface into the food interior, incorporation of these antimicrobials in WPI films and coatings maintains their presence at the food surface where they are effective.

WPI films and coatings incorporating LZ and LPOS show potential for inhibiting microorganisms already present on ready-to-eat (RTE) fish and meat products, as well as inhibiting microorganisms that contaminate previously film-wrapped or coated products. Thus, incorporation of these bioactive compounds into whey protein films and coatings has been shown to be a feasible procedure for extending the safety and stability of foods. Additional information to be obtained in the second year of the project will allow prediction of food shelf life as influenced by WPI film and coating thickness and amount of bioactive compound incorporated into the films and coatings.

Incorporation of antimicrobials or antioxidant into WPI film-forming solutions has little effect on their viscosities. Thus, there will be no negative effects on commercial film-or coating formation processes. In addition, incorporation of antimicrobials or antioxidant has no significant effect on resulting film of coating mechanical, barrier or visual properties. Thus, the other functions that the films or coatings can serve will not be compromised.

Publications (Submitted or in preparation)
Min, S., L.J. Harris, J.H. Han, J.M. Krochta. Lysozyme incorporation in whey protein isolate films and coatings for inhibition of Listeria monocytogenes. Journal of Food Protection.

Min, S., L.J. Harris, J.M. Krochta. Listeria monocytogenes inhibition by whey protein films and coatings incorporating lactoperoxidase systems. Journal of Food Science.

Min, S., L.J. Harris, J.M. Krochta. Inhibition of Salmonella enterica and Escherichia coli O157:H7 by lactoferrin, lysozyme, and lactoperoxidase systems and by edible whey protein films incorporating lactoperoxidase systems. J. of Food Science

Min, S., L.J. Harris, J.M. Krochta. Inhibition of Salmonella enterica and Escherichia coli O157:H7 inoculated on roasted turkey by edible whey protein coatings incorporating lactoperoxidase systems. Journal of Food Protection.

* Indicates continuing project