(3) Lb:St = 1:2, the effect ofxylo-oligosaccharideson the growth and acid production of yogurt fermentation strains
As can be seen from Figure 3, 0 to 1.5 h is the adaptation period of the strain and the initial stage of entering the logarithmic growth phase. The strain does not grow quickly, the pH value decreases slowly, and the acidity and lactic acid increase rapidly. When the xylo-oligosaccharide concentration is 0.8%, the total bacteria The maximum value is 1.16×108 CFU/mL (the control is 1.09×108 CFU/mL), and the pH, acidity and lactic acid content are similar to the control; between 1.5 h and 3.5 h, the strain enters the logarithmic growth phase and grows rapidly. The pH dropped rapidly, and the acidity and lactic acid content increased rapidly. When the xylo-oligosaccharide concentration was 0.8%, the maximum total bacterial count was 5.31×108 CFU/mL (the control was 5.12×108 CFU/mL). The pH, acidity, and lactic acid content They were 5.54, 57 and 5.03 respectively, and the control pH, acidity and lactic acid content were 5.68, 58 and 5.0. From 3.5 h to 4.5 h, the total bacterial count gradually decreased, the pH continued to decrease, reaching the lowest level of 5.10, and the acidity and lactic acid content gradually increased. The maximum are 63 and 5.68 respectively.
From the comparison of Figures 1 to 3, it can be seen that when the ratio of Lactobacillus bulgaricus and Streptococcus thermophilus is 1:2 or 2:1, the pH will decrease slowly and the acidity will be low, while the ratio of Lactobacillus bulgaricus and Streptococcus thermophilus is At 1:1, the addition of xylo-oligosaccharides can promote the growth of yogurt fermentation strains and promote acid production, thus shortening the fermentation time.
Test Conclusions
This article studied the effect of prebiotic xylo-oligosaccharide and yogurt strain ratio on the total bacterial count, pH and acidity during yogurt fermentation. The mass fraction of xylo-oligosaccharide was 0, 0.5%, 0.6%, 0.7%, 0.8%, 0.9 %, 1.0%, the ratios of Lactobacillus bulgaricus and Streptococcus thermophilus (Lb:St) were 2:1, 1:1 and 1:2 respectively. The results showed that the optimal ratio of Lb:St was 1:1, low The optimal addition amount of xylose is 0.8%. After fermentation at 42°C for 3.5 hours, the total bacterial count reaches the maximum value of 7.14×108 CFU/mL (the control is 5.92×108 CFU/mL), and the pH value is 4.51 (the control is 5.09). ), the acidity reaches 72°T (the control is 64°T), and the lactic acid content is 6.45 mg/mL (the control is 5.77 mg/mL). Therefore, the addition of xylo-oligosaccharides can promote the growth of yogurt fermentation strains, acid production and Shorten fermentation time.
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Post time: Nov-14-2023
