Manufacture of a Dairy Dessert from Ultra-High Temperature Milk Concentrate

The purpose of this project was to initiate development of a nonrefrigerated dairy dessert product. Milk was concentrated by pressure-driven filtration and then sterilized using ultra-high temperature (UHT) processing. Following sterilization, samples were aseptically inoculated with rennet to coagulate the milk, which was then stored at room temperature. These processing steps produced a dairy dessert that did not require refrigeration. I investigated the influence of total solids, milk fat, rennet dosage, storage temperature, and storage time on curd firmness and syneresis. I investigated the effect on curd firmness and syneresis of giving the concentrate a heat treatment prior to UHT processing. Chocolate and vanilla dairy desserts were prepared, and a taste panel was conducted to compare the dairy dessert with a ready-to- eat starch-based pudding. Milk concentrate obtained by reverse osmosis did not form a gel, whereas concentrate obtained by ultrafiltration did gel. Increasing the solids content of the milk concentrate increased curd firmness, but increasing the fat content of the concentrate decreased curd firmness. Curd firmness and syneresis increased as the concentration of rennet was increased. Products stored at 21°C yielded firmer gels with more syneresis than products stored at 4°C. Moreover, products stored for longer periods of time produced firmer gels and greater amounts of syneresis. Concentrate that received a batch heat treatment prior to sterilization reduced syneresis. The addition of cocoa to the concentrate inhibited coagulation. Taste panelists preferred the commercial pudding over the dairy dessert. Increasing the sugar content of the dairy dessert may improve its sensory properties. To produce a commercially viable product, additional work is required on flavor development