Isolation of lactic whey proteins in the form of complexes with apple -pectin A. V. SEROV, Yu. A. A h i o w v and V. B. TOLSTOGUZOV The possibility of isolating lactic whey proteins (LWP) in the form of insoluble complexes (IC) with apple pectin was studied. The effect of pH, ionic strength (p, NaCI), temperature (T "C), pectin weight fraction ( X , 76) and the total concentration of macromolecular components in the system (W,) on isolation has been considered. The process has been characterized by L W P yield in the composition IC -P, percentage and the extent of protein concentration in the concentrated phase (IC) -F. The mixing of lactic whey with a pectin solution usually yielded an IC (10 "/, 5 X, 90 %). The dependence of P on X , is of an extreme nature with a maximum of 85 % at X , = 60%. The following conditions correspond to the maximum L W P yield (90",) in the complex composition: pH 3.4, p = 0.01, T = 5-20 "C, X , = 6076, W, = 0.5%. At compositions of the system corresponding to the maximum P value ( X , = 60 x) practically all the L W P fractions are present in the concentrated phase. If X , p 60 p: or X , < 60 "/, cc-lactalbumin is practically absent in the concentrated phase. Usually, minimum F values (2.5-4.0) correspond to maximum protein yield at X, = 60%. At X, > 70 and X , < 50 % F values may be considerably higher (20 times and more). A decrease in the pectin methylation degree from 56.7% down to 15.4% does not affect F. The maximum protein yield (94%) occurs when low methylated pectin is used. The character of the dependence of F on X , is explained according to similar processes of complex gel formation and the processes of gel formation in polymer solutions.