Unveiling the Potential of Probiotic-Enriched Yogurt via Bacterial Fermentation

Yogurt has a jelly-like structure with consistent viscosity. It is made by using lactic starter culture which lactic acid bacteria ferments lactose, or milk sugar, through its enzymes. Common starter culture includes combination of Streptococcus thermophilus and Lactobacillus bulgaricus. The pasteurized milk and yogurt starter culture was poured into 4 styrofoam cups. One of the four styrofoam cup was put used for pH and TSS monitoring. The pH of yogurt changed from 6.5 down to 4.23 indicating yogurt has become acidic and gave a sour acidic flavor with a light taste. The sugar content of the yogurt changed from 11 and went up to 12 upon adding the starter culture then went down to 8 after the fermentation. The texture of the yogurt changed from watery to smooth, pudding-like. Moreover, the appearance of the yogurt went from creamy to a thick, slightly firm with a dripping consistency. While the color of the yogurt changed from naturally white to yellowish white. In conclusion, a yogurt can be made from the live bacteria out of a commercial regular yogurt. Therefore, it is possible that a homemade yogurt can be made locally and economically.酸奶呈胶状结构，黏度均匀稳定。其制备采用乳酸菌发酵剂，乳酸菌通过自身酶系发酵乳糖（又称乳糖）。常用发酵剂包含嗜热链球菌（Streptococcus thermophilus）与保加利亚乳杆菌（Lactobacillus bulgaricus）的混合菌株。将巴氏杀菌乳与酸奶发酵剂倒入4个泡沫塑料杯中，其中1个泡沫塑料杯用于pH值与总可溶性固形物（Total Soluble Solids, TSS）的监测。酸奶的pH值从6.5降至4.23，表明其已呈酸性，带有清爽的酸味风味。添加发酵剂后，酸奶的糖含量由11升至12，发酵完成后降至8。酸奶的质地由稀水样变为顺滑的布丁状。此外，酸奶的外观由乳脂状变为浓稠、略带紧实且具有滴落性的质地，其色泽则由天然乳白色变为米黄色。综上，可利用市售普通酸奶中的活性菌株制备酸奶，因此可在本地以经济可行的方式自制酸奶。