In this experiment, citrus fiber, beet fiber and agar were used to develop a low-sugar, high-fiber room-temperature fermented yogurt, and the texture and sensory quality of yogurt samples made with their combinations in different proportions were evaluated. Lactase and Sweety T-1, a mixed commercial starter culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were used to completely decompose lactose in milk to produce glucose with higher sweetness, thereby improving the sweetness of low-sugar yogurt. The results showed that adding 3% citrus fiber, 0.2% agar and 1% beet fiber imparted good stability and high sensory score to low-sugar, high-fiber room-temperature fermented yogurt. Raw milk was inoculated 200 U/L Sweety T-1 with the addition of 1 600 BLU/L lactase and without the addition of any sugar or sweetener and was fermented at 42 ℃. After 12 h, lactose was completely decomposed, producing 2.5% glucose.

In the manufacturing process of long shelf-life yogurt, there are many factors that may affect its quality, including pasteurization temperature and time, the homogenization degree of stirred mixtures, and filling temperature. The shelf life of yogurt can be extended by choosing a proper pasteurization temperature and time taking the product quality into account, and its texture can be improved by selecting a suitable homogenization approach, which is also beneficial to more uniformly heating yoghurt during sterilization, avoiding the collapse of the system. The recovery of yogurt viscosity can be affected by filling temperature. A proper filling temperature should be selected to reach the requirements of quality design during the manufacturing of yogurt.