Changes in the Quality of Plain Yogurt Made From Cow’s, Goat’s, and Sheep’s Milk Within the Shelf Life

Abstract

Abstract The aim of this study was to compare selected physicochemical properties, the fatty acid profile, and the content of vitamins A and E in plain yogurt (Y) made from cow’s (YC), goat’s (YG), and sheep’s milk (YS), and to monitor changes in these parameters within the shelf life of the analyzed products. The products were supplied by three manufacturers. Each group consisted of yogurts from three different batches, and each batch was represented by two products. The quality of the first product was analyzed in the middle of shelf life, and the quality of the second product was analyzed at the end of shelf life (E, last day). The products were stored at a temperature of 4○C until analysis. An analysis performed at date M demonstrated that YC had the highest (p ≤ 0.05) values of yellowness (b*) and titratable acidity, and the lowest (p ≤ 0.05) content of vitamins A and E; YG had the highest (p ≤ 0.05) values of redness (a*) and the lowest (p ≤ 0.05) value of b*; YS had the highest (p ≤ 0.05) values of lightness (L*) and pH, the highest (p ≤ 0.05) content of vitamins A and E, and the lowest (p ≤ 0.05) values of a* and titratable acidity. YC and YS were characterized by higher (p ≤ 0.05) values of chroma (C*) than YG. YC and YG were characterized by higher (p ≤ 0.05) values of UFA/SFA, MUFA/SFA, DFA/OFA, and n-6/n-3 PUFA ratios, compared with YS. The n-6/n-3 PUFA ratio was also higher (p ≤ 0.05) in YG than in YC. In comparison with YC, YG and YS had higher (p ≤ 0.05) values of the PUFA/SFA ratio and EFA concentrations, and the highest (p ≤ 0.05) values were noted in YS. Measurements conducted at date E revealed a decrease (p ≤ 0.05) in the value of a* and vitamin E content in YC, an increase in the value of L* in YG, and an increase in the value of a*, a decrease in the values of b*, C* and pH, and a decrease in vitamin E content in YS. Titratable acidity increased (p ≤ 0.05) in all types of Y. Changes in the nutritional value of fat (a decrease in the values of UFA/SFA, MUFA/SFA, and PUFA/SFA ratios, a decrease in EFA concentrations, and an increase in the n-6/n-3 PUFA ratio) were significant (p ≤ 0.05) only in YC. The results of the study indicate that YG was characterized by the highest stability, and YC was characterized by the lowest stability during storage.