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J. J. RESCH, C. R. Daubert, and E. A. Foegeding. Dept. of Food Science, North Carolina State Univ., Box 7624, Raleigh, NC 27695-7624 A derivatization process consisting of protein hydration, thermal gelation under acidic conditions, and drying was established to modify whey proteins into an ingredient offering instant thickening and cold gelling functionality similar to starches and hydrocolloids. Acidulant selection and pH adjustment are crucial, albeit poorly understood, elements of this procedure. Preliminary data suggested different food acidulants may produce modified ingredients with a range of functional attributes. The objectives of this study were 1) to examine how different acidulant systems impact the rheological properties of heat-induced whey protein gels and the powders derived from these gels and 2) to use these results to manipulate the effectiveness of the modification process. The established derivatization procedure was applied to a commercial beta-lactoglobulin ingredient using hydrochloric, lactic, phosphoric, and citric acids. Large and small strain rheological techniques and electron microscopy studies were used to characterize the gel structures formed during the initial stage of the derivatization process. The functionality of the powders rendered by freeze-drying and milling of these gels was described with rotational viscometry and small amplitude oscillatory rheology. Acidulant type had a dramatic effect on gel properties and derivatized powder functionality. Translucent, fine-stranded gels made with hydrochloric and lactic acid yielded effective instant thickening powders upon drying. Citric acid usage led to rapidly-formed opaque, particulate gels unsuitable for creating instant thickeners. Gels made with phosphoric acid were very weak and formed slowly at 80 °C. Analysis of the acidulant effects revealed ion specific abilities to alter protein aggregation, denaturation, and gelation. The results enabled processing conditions to be manipulated to improve gel characteristics and derivatized powder functionality for systems using phosphoric, lactic and hydrochloric acids. This information permits selection of an acidulant that would give the best functionality and sensory attributes for a specific application while meeting cost, labeling, and marketing restrictions.
Session 64, Dairy Foods: Milk proteins
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