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Enzymatic deamidation reduces flavor binding problems in high protein-containing products.

Food protein functional properties are determined by how the proteins are arranged structurally in food systems. Altering the chemistry of food proteins can improve such functional properties as solubility, viscosity, gelation, fat emulsification and foaming ability.

The conversion of protein amide groups to carboxyl groups by deamidation improves solubility and other physical properties of proteins under mildly acidic conditions. And, optimizing the solubility, emulsifying or foaming properties of edible proteins enhances their use as functional ingredients in beverages, pourable and nonpourable dressings, whipped toppings, frozen desserts, confections, baked goods and meat.

An enzymatic approach to protein deamidation has advantages over a chemical approach, including speed of reaction. Also, reactions take place under mild conditions, such as neutral pH and room temperature, and are highly specific. The mild conditions reduce energy costs. The high specificity increases processing efficiency and minimizes the need for downstream processing.

Scientists at the University of Illinois studied how enzymatic deamidation by protein-glutaminase would affect the protein solubility and flavor binding potential of soymilk. Their work can facilitate development of technology to produce protein-containing foods with improved functional properties, especially protein solubility, and potentially decreased flavor fade problems associated with flavor-protein interactions.

Treating soymilk with protein-glutaminase for two hours at 44 C, using an enzyme-to-substrate ratio of 40 U per gram of protein, resulted in a high degree of protein deamidation--66.4%--and a relatively low degree of protein hydrolysis--4.25%.

The deamidated and control soymilks did not differ with respect to aroma. But they differed in taste characteristics as examined by sensory evaluation. Protein solubility in the deamidated samples was enhanced at weakly acidic conditions--pH 5.0--but did not differ from non-deamidated soymilk at pH values of 3.0 and 7.0.

Odor detection thresholds for the flavor compounds vanillin and maltol were approximately five- and three-fold lower, respectively, in the deamidated samples compared with the control soymilks. The deamidated samples had a lower flavor binding potential than did the control soymilks. So, it appears that protein-glutaminase deamidation can reduce flavor binding problems encountered in high protein-containing foods and beverages.

Further information. Keith R. Cadwallader, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 1302 West Pennsylvania Ave., Urbana, IL 61801; phone: 217-244-4498; email:
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Publication:Emerging Food R&D Report
Date:Jun 1, 2013
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