Processing parameter effects on the functional properties of derivatized whey protein ingredients
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2004-03-12
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Abstract
Processing parameters, including protein starting material, drying technique, acidulant selection, and heating conditions, were investigated to improve and better understand a novel procedure for the modification of whey proteins into an ingredient capable of cold-set thickening, water holding, and weak gelling. The derivatization procedure, consisting of protein hydration, pH adjustment, thermal gelation, drying, and milling, was made more cost effective by applying the process to whey protein concentrates (WPC) with protein contents of 86, 74, and 64 %. Although the composition of the starting materials influenced the functionality of the final derivatized powders, all samples exhibited a dramatic increase in thickening and water holding ability and were able to form cold-set weak gel structures suitable for contributing viscosity and texture to a wide range of food systems.
Further improvements to the derivatization process were made by developing a modification to the procedure utilizing spray drying in place of the original freeze drying operation. Rheological characterization revealed the modified derivatization procedure yielded an ingredient with cold-set thickening and gelling abilities similar to the original derivatized powder. The modified whey proteins were also able to achieve, at higher usage levels, textural properties comparable to several polysaccharide thickeners. Incorporation of spray drying created a more economical process for the expanded production of an instant thickening whey protein ingredient.
Investigation of hydrochloric, lactic, citric, and phosphoric acids revealed acidulant selection is an important processing parameter that may modify β-lactoglobulin (β-Lg) gelation and the functional properties of derivatized thickening ingredients. Dramatic acid-specific effects on the rheological and microstructural properties of β-Lg gels and the functionality of derivatized β-Lg powders were in general agreement with classical Hofmeister series behavior. Maximum viscosity and water holding were observed in the derivatized ingredients derived from the strong, translucent gels created in systems utilizing lactic and hydrochloric acids. Use of citric acid resulted in a brittle, opaque coagulum which created a derivatized ingredient with very poor functionality. Protein solutions treated with phosphoric acid were most resistant to gelation at 80 °C and led to limited thickening ability of the derivatized powder.
Characterization of acidulant effects and their relative influence on the stability of protein conformation enabled heating conditions to be manipulated to improve attributes of β-Lg gels and instant thickening powders. As isothermal gelation temperature was increased from 75 to 85 °C, gels made with hydrochloric and lactic acid showed more rapid gel formation and increased stress at gel fracture. Thickening and water holding properties of powders derived from these gels also increased with temperature. Gels and derivatized powders prepared with phosphoric acid exhibited attributes similar to samples prepared with hydrochloric and lactic acid at lower temperatures. The ion specific ability of phosphate to increase denaturation temperature was responsible for the shift in properties of gels made with phosphoric acid. By heating to a temperature of 90 °C, systems made with phosphoric acid achieved gelation and derivatized powder performance similar to systems utilizing hydrochloric or lactic acids. Acid selection and gelation temperature offer alternatives to control β-Lg gel strength and the functional properties of instant thickening protein ingredients.
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Keywords
heating rate, freeze drying, spray-drying, acidulants, derivatization, gelation, beta-lactoglobulin, whey protein
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Degree
PhD
Discipline
Food Science
