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Aggregation and gelation characteristics of high protein dairy ingredient powders
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University College Cork
Milk protein-containing dairy ingredient powders are used extensively in the formulation of a wide range of foods and beverages. Protein is an essential component in such food systems, where it provides nutrition and a range of functionalities including rennet gelation, heat stability, ethanol stability and acid gelation, which influence the manufacture and stabilization of the foods. The protein dispersed in water is typically subjected to various processes, including concentration, homogenization, heating, acidification, in the presence of other formulation constituents (e.g., salts, sugars, ethanol, and acids) during food processing. The exposure of proteins to different processing steps and other constituents can significantly alter their aggregation behaviour, and hence, stability. The current study investigated the changes in compositional, physico-chemical and functional properties of skim milk and protein-based dispersions such as reconstituted skim milk, protein-fortified milk, and reconstituted milk protein concentrate, which resulted from seasonal variations, fortification of milk with different high protein ingredients, processing operations (heat treatment, evaporation and spray-drying) during the manufacture of skim milk powder, at pH during milk heat treatment followed by restoration of pH after heat treatment. Seasonal variations in proportion of spring- and autumn-calving milk in mixed-herd milk and in milk composition were characterized. Key factors influencing the functionality of the milk protein included the calcium-phosphate content, heat treatment of milk during powder manufacture, pH adjustment prior to heat treatment, and the composition of the solvent. These factors exerted their effects by altering one or more physicochemical parameters of the reconstituted ingredients, including denaturation of whey protein, complexation of denatured whey proteins with dissociated κ-casein or casein micelles, partitioning of individual caseins and minerals between the serum and the casein micelle, casein micelle size and charge. The results of the current studies have expanded our knowledge of the factors affecting key functional parameters of reconstituted milk protein powders, and provide mechanistic bases for understanding how these factors exert their effects.
Rennet gelation , Heat stability , Ethanol stability , Milk protein
Lin, Y. 2017. Aggregation and gelation characteristics of high protein dairy ingredient powders. PhD Thesis, University College Cork.