Polymerization, other interactions influence whey powder foaming.

Sweet whey powder (SWP), a valuable byproduct of cheese processing, is used for its functionality. SWP is produced by drying fresh whey from which the milkfat has been removed during the preparation of Cheddar, Mozzarella, Swiss or other cheeses manufactured principally with rennet type enzymes--casein-coagulating enzyme preparations. SWP contains all of the constituents, except water, in the same relative proportion as in liquid whey. Its pH in a 10% solution should be greater than 5.6.

High levels of lactose in SWP contribute to browning, while proteins participate in various foaming, gelling and emulsifying processes. Scientists have learned that the foaming capacity of SWP can vary greatly. This variation may be influenced by the availability of amphiphilic proteins and peptides.

University of Wisconsin researchers characterized the protein composition of SWP as it related to its foaming properties. Investigators studied the protein composition of SWP samples with high-, medium- and low-foaming capacities. They purified and enriched the 1% samples using centrifugal ultrafiltration. The proteins were characterized for protein composition.

Foams were formed and were drained separately. The scientists further purified and enriched the draining liquid, which was then electrophoresed. Investigators studied the polypeptide profiles of samples and foams using Tris-tricene gels. Similar experiments were performed on heat-treated samples.

Researchers found the presence of protein aggregates and beta-lactoglobulin (beta-1g) octamers (144 KDa) in low-foaming and medium-foaming samples. High-foaming samples did not show prominent bands of beta-1g octamer or protein aggregates. High-foaming samples contained beta-1g and alpha-lactalbumin in higher proportions, with negligible amounts of protein aggregates, beta-1g octamers and albumin. Heat treatments of low-foaming samples improved foaming in some cases. However, the protein composition did not change from that found in native samples. There were no differences in the protein compositions of the sample and respective foam.

It appears that the degree of polymerization, proportion of beta-1g and protein-protein interactions may have a role in establishing the foaming properties of SWP. Understanding the concepts related to the foaming process will help in modifying manufacturing processes to obtain SWP of desired foaming character.

Further information. Dattatreya Banavara, Department of Food Science, University of Wisconsin-Madison, 1605 Linden Dr., 204 Babcock Hall, Madison, WI 53706; phone: [phone]; email: [e-mail].