Effect of Lacticaseibacillus paracasei on the Stability of Fermented Milk

To investigate the effect of five strains of Lacticaseibacillus paracasei on the stability of fermented milk, the changes in stability during storage were determined by whey precipitation rate, rheology, texture, Zeta potential, particle size and Lumisizer analysis of fermented milk made by different strains. The results showed that Lacticaseibacillus paracasei BDII had the lowest whey precipitation rate during storage, 24.62% at 1 d, 29.44% at 4 d, and 28.73% at 7 d, and then J4 exhibited the highest whey precipitation rate, reaching 43.75% at 1 d, 42.55% at 4 d, and 38.55% at 7 d. Lacticaseibacillus paracasei BDII significantly improved the rheological and textural properties of fermented milk, the storage modulus and loss modulus of BDII fermented milk during the storage period showed the same trend as those of J4, STI-13, which were slower, while the storage modulus of BDII increased from 67.20 to 88.80 Pa, and the loss modulus increased from 23.60 to 42.90 Pa. The hardness of BDII fermented milk increased from 68.00 to 85.00 g·sec, the viscosity increased from 127.00 to 145.00 g·sec. In addition, the Zeta potential of BDII fermented milk increased gradually with the storage time and the trend was the smallest during the period, which only increased by 2.50 mV. The particle size of BDII fermented milk had the same trend as that of J17, the same stability. Lumisizer analysis revealed that BDII fermented milk had the smallest amount of whey precipitated, the lowest light transmission rate, and the best stability. In conclusion, the fermented milk made by different strains have different stability, among which the fermented milk of Lacticaseibacillus paracasei BDII fermented milk has a uniform and delicate texture and the best storage stability. These results provide a new reference for the study of the stability of fermented milk.