Starch gelatinization inside a whey protein gel formed by cold gelation

Native potato starch (PS) granules were trapped within a whey protein network formed by cold gelation. Heat treatment of these composite gels induced PS gelatinization inside the protein network, which was studied with a DSC/hot-stage system and confocal laser scanning microscopy. Gelatinization inside the protein network was also indirectly followed by rheological measurements and mechanical properties of the composite gels measured before and after heat treatment. The presence of the protein network shortened the gelatinization by 3 degrees C, reduced the gelatinization enthalpy by 42% and significantly restricted granules swelling. The rheological and mechanical properties of the gels were influenced by PS swelling, depending on starch concentration. After reheating to 90 degrees C, the addition of 1% PS resulted in a weakening of the gel. However, the addition of 9% PS led to a reinforcement of the gel, probably due to the formation of an interpenetrating network between whey proteins and the gelatinized PS.