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E. A. FOEGEDING, Dept. of Food Science, North Carolina State Univ., Schaub Hall, Box 7624, Raleigh, NC 27695-7624 A common concern with whey protein-containing drinks is the level of astringency. This problem is most pronounced in drinks made at pH values less than or equal to 3.0. As defined, astringency is a drying and/or puckering sensation brought on by stimulants such as alums or tannins. Moreover, with polyphenols, astringency is caused by polyphenols forming complexes with proline-rich proteins from saliva, producing large aggregates. This begs the question of what do polyphenols, alum, and whey proteins have in common that would cause astringency? The common mechanism could be forming a complex with proline-rich proteins from saliva. This is accomplished with hydrophobic interactions, in the case of polyphenols, and electrostatic interactions with the trivalent aluminum cation in alum. In whey proteins, the precise mechanism is not known, but it is possible that combinations of electrostatic and hydrophobic interactions are involved. Astringency of whey protein-containing drinks was investigated by comparing 3% w/v protein drinks made from either whey protein isolate, alpha-lactalbumin, or beta-lactoglobulin. The drinks were adjusted to pH 3.0 or 7.0, and either heated (80°C for 30 min) or not heated. The results showed that astringency was related to the pH, and not the type of protein. At pH 3.0, the net charge on the majority of whey proteins would be positive, similar to the charge on aluminum in alum. Therefore, we speculated that the cause of astringency in low pH, whey protein-containing beverages is complex formation between positively charged whey proteins and the proline-rich proteins from saliva. Ongoing studies aimed at proving this mechanism will be discussed.
Session 47, Sensory analysis of texture in dairy products
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |