17B-15 |
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A. DATTATREYA and S. A. Rankin. Dept. of Food Science, Univ. of Wisconsin, Madison, 1605 Linden Dr., 218 Babcock Hall, Madison, WI 53706-1519 Color of freshly dried whey powder is white with slight yellowish-green hue. During storage, it may acquire an undesirable brown color. Dried wheys show considerable variation in the rate at which they darken and this has been attributed to various factors. Alkaline pHs have been reported to increase the rate of browning in model sugar- amino acid buffer systems. It is possible that the liquid whey may be subjected to various holding times and temperatures before drying, which might cause a change in pH, thus affecting the browning potential of whey powders during storage. The objective of this study was to determine the effect of pH on the browning of whey powders. Spray-dried whey powders of pHs’ typical of manufacturing, were subjected to storage at various temperatures in open and sealed containers. The pH of dry whey powders was modified by exposure to vaporous acetic acid. Also, liquid whey was acidified with lactic acid to different pHs, then freeze dried. Browning was studied at various time-temperature conditions as measured using a colorimeter. The results showed that the whey powders present in sealed containers browned faster than in open. At 100°C, all dry whey samples browned within 24h. The extent of color formation was potentiated by acidic conditions. In general, browning was increased by higher temperatures; longer storage times. Similar results were obtained for the freeze dried powders. These results suggest that lowering the pH of whey powders increases the rate of browning. Understanding these effects will help in modifying the processing/handling conditions to obtain high quality whey powders which are stable to browning.
Session 17B, Dairy Foods: General
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