Effects of Salts on the Properties of Sols and Gels Prepared from Whey Protein Isolate and Process Whey Protein

¹ Research Institute for Food Science, Kyoto University, Uji, Kyoto 611-0011, Japan
² Daiichi-Kasei Co., Ltd., Okanonishi-cho 7-1, Kawata, Yamashina-ku, Kyoto 607-8323, Japan

Process whey protein was prepared by heat treatment of whey protein isolate under salt-free conditions. Addition of sodium chloride, trisodium cit-rate, potassium chloride, or calcium chloride to a process whey protein solution increased the viscosity and resulted in gelation at 25°C. In contrast, the viscosity of whey protein isolate solutions was not changed. The properties of whey protein isolate and process whey protein gels prepared by heating at 80°C for 60 min with 25 different salts were measured and compared. Although process whey protein produced gels with the addition of any of the salts examined, whey protein isolate solution did not gel with some salts. The tendency of both protein solutions to gel apparently depended on the lyotropic nature of the cation. Inorganic salts produced firmer gels than did organic salts. The gel strength and water-holding capacity of both proteins decreased as salt concentration increased. When the transparent gels prepared from process whey protein were heated again, the gel firmness increased, adhesiveness decreased, and transparency and cohesiveness slightly decreased, depending on the temperature and duration of the second heating.

Key Words: whey protein isolate • process whey protein • gelation

Submitted on May 2, 1996
Accepted on August 20, 1997

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