Characterization and application of a derivatized whey ingredient
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Date
2004-04-01
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Abstract
Whey protein is a nutritious ingredient that is manipulated to impart texture in many foods. Thermal treatment is commonly used as a means of inducing whey protein aggregation, which under suitable conditions may form gels. Unfortunately, many foods cannot or should not withstand the temperatures required to induce protein gelation, thereby limiting native whey as a thickening agent. A process for manufacturing cold-gelling whey proteins has been developed, and the resulting derivatized whey ingredient provides the food industry with more alternatives in product formulation, including superior nutritional value when compared with carbohydrate-based stabilizing systems.
The current cold-gelling whey protein derivatization procedure involves protein hydration, pH adjustment, thermal treatment, and spray drying. This process yields an easily dispersed protein powder that does not require heat or addition of salts to function as a thickening agent. Dispersions containing 9% protein (w/w) of the derivatized ingredient in deionized water display apparent viscosities of approximately 1.0 Pa s at shear rates of 50 s⁻¹. For comparison, the viscosity of a 9% protein (w/w) solution of unmodified whey is approximately 0.002 Pa s. Therefore, the derivatization process yields an ingredient with an apparent viscosity approximately 3 orders of magnitude greater than unmodified whey protein.
The derivatized whey ingredient could potentially serve a number of different functions in food systems: thickening agent, stabilizer, fat-mimicker, emulsifier, and texturizer. To test this potential, a basic understanding of ingredient interactions was needed; hence the modified whey ingredient was characterized under conditions generally encountered in food systems. The effects of protein concentration, pH, and salt on the modified whey protein ingredient were determined using model systems prepared as dispersions or solutions at controlled pH, temperature, and salt concentration. Water holding and viscosity imparted by the modified whey ingredient were dependent on protein concentration, pH, and salt concentration. The effective concentration, or the concentration at which dilute dispersions enter a concentrated regime, was approximately 7% (w/w) protein. Effective concentration increased, and water holding and viscosity decreased as the pH of modified protein dispersions approached the isoelectric point (pI) of whey protein (~5.2). Furthermore, water holding and viscosity decreased as salt concentration of modified whey protein dispersions increased.
Additional studies characterized the emulsifying and foaming properties of the modified whey protein ingredient. Emulsifying capacity, or the amount of oil a protein can adsorb, of the modified whey protein ingredient was similar to that of unmodified whey at pH 3.4 and 6.8. However, the modified whey ingredient created a more stable emulsion than unmodified whey at an equivalent pH. The modified whey protein ingredient created more stable foams that had lower overrun than unmodified whey protein foams. Unlike unmodified whey protein foams, stiffness of modified whey protein foams was improved through pH adjustment.
Dairy food applications traditionally stabilized with starch were targeted for application of the modified whey protein ingredient because the modified ingredient had proven to hold water and add viscosity similar to modified starch. Comparisons of yogurt containing 2% (w/w) unmodified whey protein and yogurt containing 2% (w/w) of the derivatized whey ingredient showed the modified ingredient improved yogurt water holding capacity. Yogurt in which starch was completely replaced with modified protein displayed higher yield stress than yogurt formulated with starch. The derivatized whey ingredient's ability to stabilize sour cream was also investigated. Increasing the level of modified whey protein from 2% (w/w) protein to 4% (w/w) protein in sour cream resulted in increased yield stress, and viscosity. However, neither modified whey protein formulation achieved yield stress or syneresis results similar to sour cream formulated with 2% (w/w) starch. Although preliminary results were promising, further optimization of yogurt and sour cream formulations with the modified whey ingredient is needed.
Based on this research, derivatized whey ingredients are likely to prove an extremely useful ingredient in dairy food applications. Replacing non-protein stabilizers with a derivatized whey protein ingredient may provide food processors the opportunity to tailor ingredient labels for diet conscious consumers. For example, replacing carbohydrate-based thickeners with protein thickeners would provide a more appealing label for low-carbohydrate dieters. Furthermore, substituting stabilizers with the derivatized whey protein ingredient will give dairy food manufacturers the option of claiming an 'all-dairy' product.
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Keywords
whey protein, rheology, derivatization
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Degree
MS
Discipline
Food Science
