The effects of acidulant type on the rheological properties of beta-lactoglobulin gels and powders derived from these gels

Heat-induced beta-lactoglobulin (β-Lg) gels and instantly-thickening protein powders derived from these gels were rheologically characterized to identify how acid selection and pH adjustment impact whey protein gelation and derived powder properties. An established procedure for the production of an instant-thickening whey protein ingredient, consisting of protein hydration, pH adjustment to 3.35, thermal gelation at 80 °C, and drying, was applied to β-Lg. Hydrochloric, lactic, citric, and phosphoric acids were evaluated in the critical pH adjustment step. Acidulant selection clearly impacted β-Lg gelation and derived powder properties. Ion specific effects were in general agreement with classical Hofmeister series behavior. Maximum viscosity and water holding were observed in the 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 an ingredient with very poor thickening functionality. Protein solutions treated with phosphoric acid were most resistant to gelation at 80 °C and led to limited thickening ability of the derived powder. Acidulant selection is an important processing parameter that may be manipulated to modify β-Lg gelation and the functional properties of derived thickening ingredients.