INTERFACIAL BEHAVIOR OF SECALIN AND RYE FLOUR-MILLING STREAMS IN COMPARISON WITH GLIADIN

Secalin was extracted from rye flour and analysed by sodium dodecyl su lphate-polyacrylamide gel electrophoresis (SDS-PAGE). The SDS-gel patt ern showed that some proteins were composed of disulphide linked polyp eptide chains. However, a gliadin sample contained more polymeric prot ein. The behaviour of gliadin and secalin at the air-water interface w as compared using the surface balance technique. It was found that sec alin was more surface,active than gliadin, spreading faster and to a h igher surface pressure. The influence of pH on the interfacial behavio ur was also studied. The surface pressure after 15 min equilibrium of both gliadin and secalin decreased with decreasing pH. The effect was independent of the acid (hydrochloric acid, lactic acid or ascorbic ac id) when compared at the same pH. The behaviour at the gas-liquid inte rface of five different rye hour-milling streams together with the who le (straight run) flour was also investigated. The fraction with highe st protein content spread fastest and reached the highest surface pres sure value. When spread on ascorbic acid at pH 3.7 the surface pressur e of the flour stream with lowest protein content decreased to the gre atest extent, whereas the fraction with the highest protein content wa s not affected. It was thus found that, although secalin showed an int erfacial behaviour similar to gliadin, this behaviour was not necessar ily shown by the total protein mixture in a rye flour. (C) 1997 Academ ic Press Limited.