Optimization of protein precipitation in acid whey obtained from small ruminant's milk

Attempts to maximize the precipitation yield of the major proteins via thermal processing of whey obtained from milks of Portuguese native breeds of ewes and goats was done using heating time, heating temperature, and stirring rate as independently manipulated variables. The experiments were planned according to afull factorial design with eight cornerpoints, six axial points, and three replicated center points. Assessment of the fractions of P-lactoglobulin and a-lactalbumin removed by precipitation was done by gel filtration chromatography. The loci of the values of each manipulated variable (when the remaining two arehed) which lead to critical points were obtained for both proteins, and the nature of such points was found. Comparative evaluation of the various loci has indicated that maxima for the precipitation of a-lactalbumin and p-lactoglobulin from both whey sources exist. However, a maximum value for the selectivity of precipitation of P-lactoglobulin relative to that of a-lactalbumin (within physically realizable conditions and without extrapolation from the experimental range covered) exists only for goat’s whey (at a temperature of ca. 92C, heating time of ca. 46 min, and stirring rate of ca. 79 r.p.m.1.