Stability of emulsions containing highly hydrolyzed whey protein and starch during retort treatments

The influence of added unmodified amylopectin starch and modified amylopectin starch on the stability of oil-in-water emulsions (4 wt% corn oil), formed with a highly hydrolyzed commercial whey protein (WPH) product, during retort treatment (121 degrees C for 16 min), was examined. The creaming, coalescence, and flocculation of the emulsions were studied by determining changes in the droplet size and the microstructure of the emulsions after retorting. At a low starch concentration (<= 1.5%), the extent of coalescence was higher in the emulsions containing modified amylopectin starch than in those containing unmodified amylopectin starch. All emulsions containing moderate levels of unmodified or modified amylopectin starch showed flocculation of oil droplets by a depletion mechanism. The degree of flocculation, which was dependent on the molecular weight and the radius of gyration of the amylopectin molecules, was considered to correlate with the extent of coalescence of the oil droplets in these emulsions. At high levels of added starch (>1.5%a), the degree of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase.