The effect of storage time and temperature on the quality of natural yoghurt
Małgorzata Jakubowska, T. Karamucki
Abstract
Cooling temperature and storage time have a significant effect on the quality of natural yogurts and their durability in retail. The aim of the study was to perform a physicochemical, microbiological and organoleptic assessment of commercial yogurt, immediately after purchase and during 3 weeks of storage at 2C and 8C. The following physicochemical parameters were measured: pH, titratable acidity, color (CIEL a*, b*) and basic chemical composition. The organoleptic assessment included the general appearance and color, consistency, aroma and taste and desirability of yogurt. Microbiological tests have determined the amount of Lactobacillus, Streptococcus, Enterobacteriaceae bacteria, and checked the presence of mold and fungi. We have observed a significant effect of storage time on titratable and active acidity in the tested samples. No statistically significant effect of storage time on color of yogurt was observed. As the storage time increased, the number of yogurt microorganisms was decreasing. The minimum normative total amount of lactic acid bacteria was recorded on the day of purchase and after one week of storage at 8C. As the storage time and the storage temperature increased, the taste and aroma of yogurt was decreasing significantly.