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Lowering pH of whey powder increases rate of browning.

The color of freshly dried whey powder is white with a slight yellowish-green hue. During its storage, the powder may acquire an undesirable brown color. Dried whey shows considerable variation in the rate at which it darkens.

The material's ability to darken is caused by various factors. Alkaline pH appears to increase the rate of browning in model sugar-amino acid buffer systems. One possible cause: the liquid whey may be subjected to various holding times and temperatures before it is dried, which might cause a change in pH. This would affect the browning potential of whey powders when they are stored.

The objective of research at the University of Wisconsin was to determine the effect of pH on the browning of whey powders. Spray-dried whey powders of the pH often used in manufacturing were stored at various temperatures in open and sealed containers. Scientists found that lowering the pH of whey powders increases the rate of browning.

In their work, the researchers modified the pH of dry whey powders by exposing them to vaporous acetic acid. Also, liquid whey was acidified with lactic acid to different pHs, then freeze-dried. The investigators studied browning at different time-temperature conditions as measured using a colorimeter. The results showed that the whey powders in sealed containers browned faster than those in open containers. At 100 C, all dry whey samples browned within 24 hours. The extent of color formation was increased by acidic conditions.

In general, browning increased with higher temperatures and longer storage times. Similar results were obtained for the freeze-dried powders. Understanding the process involved here will help in modifying processing and handling conditions to obtain high-quality whey powders that are stable to browning.

Loaded with essential amino acids, whey is one of the best sources of protein for consumers. Whey is rich in branched-chain amino acids, components that provide energy for those undergoing intense or prolonged periods of exercise. But there is more to whey ingredients than nutritional appeal. Formulators are taking advantage of whey's functional properties, such as whipping and foaming, emulsification, gelation and high water-binding capabilities, to improve the taste and mouthfeel of new products or to replace fat.

Further information. Scott Rankin, Department of Food Science, University of Wisconsin, Madison, 1605 Linden Dr., A203B Babcock Hall, Madison, WI 53706; phone: 608-263-2008; fax: 608-262-6872; email:
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Publication:Emerging Food R&D Report
Date:Jan 1, 2007
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