Amino Acid Metabolism， Fermentation and Storage Characteristics of Probiotics in Fermented Milk

Objective: In this study, the fermentation and storage characteristics of probiotic fermented milk (PFM) were evaluated. Methods: Bifidobacterium animalis subsp. V9 (Bifidobacterium animalis subsp. V9), Lacticaseibacillus paracasei PC-01 (Lacticaseibacillus paracasei PC-01), and Lactiplantibacillus plantarum P-8 (Lactiplantibacillus plantarum P-8) were mixed fermented with control group compared (containing Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus). Optical microrheometer was used to monitor the rheological parameters during fermentation, the content of free amino acids at fermentation termination, the viable cell count, titrable acidity (TA), and other physical and chemical indexes during storage. Result: The fermented milk of probiotics showed high viscosity factor, high solid-liquid equilibrium value, low elasticity factor, and low flow state. Fourteen kinds of free amino acids were detected at the end of fermentation, among which eight kinds of amino acids were significantly increased, content of phenylalanine (0.93 mg/kg), valine (3.3 mg/kg), alanine (22.6 mg/kg), lysine (12.6 mg/kg), threonine (3.8 mg/kg), serine (3.5 mg/kg), proline (35.4 mg/kg) and leucine (5.4 mg/kg). The viable cell counts of Lactobacillus and V9 in PFM group was 2.341108 CFU/mL at storage initial and 3.431107 CFU/mL at the end of storage (28 d), respectively. Compared with the control group (FM), there were no significant differences in pH value, TA, and water holding capacity, and the viscosity was significantly reduced (P<0.01), and sensory taste score was significantly increased (P<0.05). Conclusion: The PFM group has excellent fermentation and storage characteristics, which can provide data support and theoretical basis for the industrial production of probiotic fermented dairy products. © 2023 Chinese Institute of Food Science and Technology. All rights reserved.