Detección de suero de quesería en leches ultrapasteurizadas mexicanas mediante la cuarta derivada del espectro de absorción

presence of rennet whey solids in ultrapasteurized milk (uht) commercialized in mexico city was determined using fourth derivative of absorption spectrum method, which allows to know the variation in whey protein/total protein ratio (wp/tp). the quantification of wp/tp ratio was used as an indicator of adulteration with rennet whey solids. the method was standardized to evaluate the accuracy, linearity and repeatability by rennet whey addition in concentrations between 0-15%, in raw milk. thirty samples of skim ultrapasteurized milk were analyzed during september, october and november; found values were compared to the ones of raw milk added with rennet whey solids (0-15%, in levels of 2.5%). a marginal difference was found in the wp/tp ratio for the 0% concentration between the two types of milk, while the rest of the concentrations showed a high significance (p < 0.01). values above 13.5% of wp/tp showed rennet whey solids addition; 36.7% of the uht milk samples were between 5% and 12% positive to rennet whey solids addition. the results indicated that fourth derivative of the absorption spectrum of the wp/tp ratio was a sensitive indicator to rennet whey solids additions.