Stimulatory Effect of Milk Protein Peptides on the Growth and Propagation of Lacticaseibacillus casei

Lacticaseibacillus casei has a slow growth rate in milk. The present study sought to assess the influence of peptides derived from milk on the growth and propagation of L. casei. The milk protein peptides were generated using flavourzyme (FPMP) or neutral protease (NPMP). The peptide concentrations of FPMP_20%-supplemented fermented milk tended to decrease throughout the fermentation process, furthermore the free amino acid (FAA) concentrations in the FPMP_20% sample (409.96 mg/kg) were much higher than in the control fermented milk (FM, 62.48 mg/kg) and NPMP_20% samples (226.34 mg/kg), indicating that FPMP could be well utilized by L. casei. The FPMP_20% sample reached the pH end-point of 3.7 at 42 h, while NPMP_20% and FM reached the same pH end-point at 67 h and 90 h. Although NPMP promoted acidification in the early stage of fermentation, the propagation and survival of L. casei were impaired. The number of viable L. casei cells in the FPMP_20%, NPMP_20%, and FM at 72 h was 9.58, 8.61, and 8.85 log CFU/g, respectively. Moreover, the contents of critical flavour components in FPMP_20% were significantly higher than in FM and NPMP_20%. The FPMP-supplemented milk fermented with L. casei showed higher cell numbers, reduced fermentation time, and increased abundance of flavour components.