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D. S. BANAVARA and S. A. Rankin. Dept. of Food Science, Univ. of Wisconsin, Madison, 1605 Linden Dr., 218 Babcock Hall, Madison, WI 53706-1519 Sweet whey powder (SWP), a valuable byproduct of cheese industry is used in food industry for its functionality. High lactose in SWP contributes to browning while proteins participate in foaming, gelling and emulsifying. Results of previous studies demonstrated that foaming capacities varied greatly; this variation is hypothesized to be influenced by the availability of amphiphilic proteins and peptides. Our objective was to characterize the protein composition of SWP as related to foaming properties. SWP samples with high, medium and low foaming capacities were selected. Protein composition was studied using SDS-PAGE. SWP samples (1%) were purified/enriched using centrifugal ultrafiltration (3KDa cut-off) and characterized for protein composition by both reducing and non-reducing SDS-PAGE using 4-20% Tris-HCl gels. The foams formed were drained separately and the draining liquid was further purified/enriched and electrophoresed. Polypeptides profiles of samples and foams were also studied using Tris-tricene gels. Similar experiments were performed on heat treated samples. Non-reducing SDS-PAGE showed the presence of protein aggregates and b-lactoglobulin (b-lg) octamers (144KDa) in low foaming and medium foaming samples. High foaming samples did not show prominent bands of b-lg octamer or protein aggregates. Densitometric study of gels revealed that high foaming samples were found to contain b-lg and a-lactalbumin in higher proportions with negligible amounts of protein aggregates, b-lg octamers and albumin. Heat treatments of low foaming samples improved foaming in some cases. However, the protein composition was not altered from native samples. There were no differences in the protein compositions of sample and respective foam. The results suggest that degree of polymerization, proportion of b-lg and protein-protein interactions may have a role in foaming properties of SWP. Understanding the concepts related to foaming will help in modifying the manufacturing process to obtain SWP of desired foaming character.
Session 64, Dairy Foods: Milk proteins
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