Study on Dynamic Changes of Microorganisms in Freshly-made Black Milk Tea after Opening

In order to explore the dynamic changes of microorganisms during the drinking process of freshly-made commercial black milk tea, this paper took iced and hot black milk tea of 3 different brands on the market as the research object. They were placed at room temperature (25 ℃) and natural humidity for 6 h to determine the total contents of mold, yeast, coliform and bacterial colonies in the freshly-made black milk tea according to the national standard method. The results showed that compared with the 0 h, the contents of yeast, coliform and total colonies of iced black milk tea placed at 25 ℃ for 6 h significantly increased (p < 0.05). The contents ranged from 1.2×10²~2.8×10³ CFU/mL, 3.0×10²~1.4×10⁵ CFU/mL, 6.4×10⁴~2.7×10⁵ CFU/mL, respectively. No significant changes were found in the contents of mold (p > 0.05), and the contents ranged from 0 to 15 CFU/mL. When the hot black milk tea was at 25 ℃ for 6 h, no mold and yeast were detected, and the total contents of coliforms and colonies ranged from 0~9.9×10⁴ CFU/mL and 0~1.6×10⁵ CFU/mL, respectively. In conclusion, the total number of bacterial colonies and coliform groups increased after the black milk tea was unsealed. Coliform groups, bacteria and yeasts were more likely to breed after opening iced black milk tea than hot. This study provides a theoretical basis for the hygienic quality control of freshly-made milk tea, and provides guidance for consumers to drink freshly-made milk tea scientifically.