71A-50 |
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E. J. HOOG, L. H. Choi, and K. D. Hayes. Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009 Lipolysis in milk can originate from lipase enzymes native to milk or from bacteria. Most bacterial lipases survive both heat treatment and drying methods used to process whey protein concentrates and isolates. The use of whey protein powders as ingredients may be a source of off-flavors produced due to lipase synthesis of free fatty acids from triglycerides. The production of mono- and diglycerides also can have an effect on frothing and cream separation. The objective was to quantify the concentration of lipoprotein lipase (LPL) present in commercial whey protein concentrates (WPC) and isolates (WPI). LpL activity was measured using the synthetic substrate p-nitrophenylbutyrate (PNPB). The substrate was added to the whey protein samples and incubated at 37 °C. The reaction was stopped by the use of phenylmethanesulfonyl, a known inhibitor of LpL. A spectrophotometer was used to measure the color produced from PNPB and the results were compared to an LpL standard curve. Samples were obtained from eight different companies, of which there were nine samples of WPCs and thirteen samples of WPIs. The results showed that there was LpL activity in WPC and WPI. WPIs had significantly (P=0.0023) more LpL activity than the WPCs. Although all samples had LpL activity, WPC samples were not significantly (P=0.7644) different from each other, while there were four WPI samples that were significantly (P < 0.0001) different from each other. Since native LpLs are destroyed by pasteurization, remaining LpL activity would likely be attributed to bacteria. Therefore, the bacterial quality of the milk would have a significant effect on whey protein powders. Since whey proteins are used as functional ingredients in baked goods, processed meats, and yogurt, serious consideration should be given to potential unwanted lipolysis, especially with WPIs.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |