Optimization of thermal protein precipitation from acid whey

Optimum conditions were determined for protein precipitation from acid whey derived from Oaxaca-type cheese production. Protein precipitation was thermally treated at 93C, with three pH levels (4.60, 4.95 and 5.30) and three heating times (30.00, 37.50 and 45.00 min). The composition of protein concentrate was the response variable and a fourth-order model was used for the response surface analysis. The results of fit model showed an R2 = 0.784 and the heating time quadratic term had the greatest effect on the amount of protein extracted. The precipitation pattern was a seat point with two zones of high-protein extraction at 37.5C: pH 5.3?5.4 and 4.5?4.6. Both points correspond to the isoelectric points of the two main protein fractions in the acid whey, indicating protein coprecipitation.