Effect of Lactobacillus paracasei ALAC-4 with fungal inhibitory effect on the quality of yogurt during storage

In order to improve the quality of yogurt during storage and prolong the shelf-life of yogurt, using traditional fermented yogurt as the control group, the Lactobacillus bulgaricus L-14 was substituted for Lactobacillus paracasei ALAC-4 with a broad-spectrum inhibition effect, good fermentation performance, and no antagonism to Streptococcus thermophilus L-1, and was used to ferment yogurt with inoculation 1∶1 (experimental group). The effect of L. paracasei ALAC-4 on the quality of yogurt during storage was explored by determining physicochemical indexes, texture, microbiological indexes, flavor, and sensory evaluation of yogurt in two groups during storage (0-28 d) after fermentation. The results showed that L. paracasei ALAC-4 instead of L. bulgaricus L-14 could delay the decline of sensory scores, water holding capacity, viscosity, post-acidification and flavor quality during the storage period (0-28 d), inhibit the growth of fungi, and prolong the shelf-life, but the effect on the texture was small. After 28 d of storage, the sensory score of yogurt in the experimental group was 82.61, the pH, titratable acidity, water holding capacity, and viscosity were 4.6, 117 °T, 73.33% and 2 622.35 mPa·s, respectively, and the elasticity, resilience, gelatinization, hardness, cohesion and chewiness were 2.73, 0.018, 1.955 N, 10.445 N, 0.188 and 0.537 N, respectively. The logarithmic value of viable Lactococcus and Lactobacillus counts was 8.5 and 8.6, respectively during sealed storage at room temperature, no molds and yeasts were detected, and the flavor quality was good.