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

<i>Lacticaseibacillus casei</i> 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 <i>L. casei</i>. The milk protein peptides were generated using flavourzyme (FPMP) or neutral protease (NPMP). The peptide concentrations of FPMP_20%-supplemented fermented milk (FM) tended to decrease throughout the fermentation process, furthermore the free amino acid concentrations in the FPMP_20% sample (409.96 mg/kg) were much higher than in the control FM (62.48 mg/kg) and NPMP_20% samples (226.34 mg/kg), indicating that FPMP could be well utilized by <i>L. casei</i>. 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 <i>L. casei</i> were impaired. The number of viable <i>L. casei</i> 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 <i>L. casei</i> showed higher cell numbers, reduced fermentation time, and increased abundance of flavour components.