Effects of Co-fermentation with Lacticaseibacillus paracasei ProSci-92 and Lactiplantibacillus plantarum P-8 on the Quality Characteristics and Storage Stability of Fermented Milk

In this study, two probiotics, Lacticaseibacillus paracasei ProSci-92 and Lactiplantibacillus plantarum P-8, which had good probiotic properties were used as a mixed starter culture for fermented milk. For comparison, a commercial starter culture was used to prepare yogurt as a control. After completion of the fermentation at 37 ℃, fermented milk was stored at 4 ℃ for 21 days. The microrheological properties of samples during fermentation were measured, and the titratable acidity, viable count, water-holding capacity, and viscosity etc. were were measured and analyzed during the storage period.The results showed that the co-fermented sample exhibited a more pronounced increase in viscosity index and a better solid-liquid balance at the late stage of fermentation, indicating that it finally formed a tougher and more stable gel structure, although the process was slower. During storage, it maintained moderate acidity, smooth texture, good water-holding capacity and high sensory evaluation scores, which all met the requirements for fermented milk. During storage, the viable counts of both probiotics remained higher than 9.1 (lg (CFU/mL)), effectively ensuring the probiotic activity.