71A-26 |
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A. DATTATREYA and S. A. Rankin. Dept. of Food Science, Univ. of Wisconsin-Madison, 1605 Linden Dr., 110 Babcock Hall, Madison, WI 53706-1519 High-quality sweet whey powder (SWP) is a free-flowing, slightly yellowish-green ingredient. During storage, SWP can darken, acquiring an undesirable brown color. There are a number of factors which affect the browning of SWP. Our previous study showed that lowering the pH of SWP increased the rate of browning. In another study, it was observed that though the pH of a number of commercial SWPs did not vary, the degree of browning varied dramatically. The industry practice of retaining liquid whey in extended storage, followed by pH adjustment immediately before processing, may alter the browning potential of SWP. Our objective was to determine the effect of pH history on the browning of SWP. Liquid whey was subjected to three treatments before freeze-drying: (1) control (pH of 6.3), wherein the sample was freeze-dried immediately; (2) whey pH was monitored at 50 °F and maintained at 6.3 using sodium hydroxide; and (3) pH was allowed to drop to 5.2 at 50 °F and finally raised to native pH. Samples were incubated at 80 °C; the extent of browning was determined with a colorimeter. Amadori compound content and total aerobic plate count were also determined. Color measurements showed that the third treatment had the highest browning extent, followed by the second, while the control had the least. These results paralleled Amadori compound formation. The total aerobic count for both the second and third treatments increased approximately tenfold over the control. These results suggest that pH history has an effect on the browning potential of SWP. Though all the powders had the same final pH and color, the extent of browning varied as a function of pH history. Improved pH control of liquid whey may be a major factor in preserving the white appearance of SWP in storage.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |