Study on the inhibitory effect of Lactobacillus paracasei H4-11 against specific spoilage bacteria in off-flavoured rice sour soup and its flavor control

• L. paracasei H4-11 has a significant inhibitory effect on A. septicus H-MN10. • septicus H-MN10 fermented rice sour soup produced off-flavor compounds. • L. paracasei H4-11 fermentation inhibits off-flavors produced by A. septicus H-MN10. • L. paracasei fermentation promotes more aroma compounds compared with A. septicus . • A total of 13 key characteristic VFCs were identified in three experimental groups. Microbial fermentation significantly affects the flavor quality of rice sour soup. In this study, the antibacterial effect of Lactobacillus paracase i H4-11 on Acinetobacter septicus H-MN10, a specific spoilage bacterial strain in off-flavoured rice sour soup, was evaluated. HS-SPME-GC-MS/HPLC analysis was performed to analyze the flavor profiles of three fermented rice sour soup samples produced by Lactobacillus paracasei H4-11 and/or Acinetobacter septicus H-MN10. The results revealed that the minimum inhibitory concentration of Lactobacillus paracasei H4-11 fermentation supernatant against Acinetobacter septicus H-MN10 was 20%. Compared to the other two fermentation samples, the fermentation sample of Lactobacillus paracasei H4-11 significantly increased the levels of total acids, total sugars, reducing sugars, and organic acids. Furthermore, Acinetobacter septicus H-MN10 fermentation produced more off-flavour compounds in rice sour soup, such as 2-octanone, (E)-2-octenoic acid, and methacrylic acid. In contrast, fermentation involving Lactobacillus paracasei H4-11 reduced the yields of these off-flavour compounds and accumulated more aroma compounds, such as ethyl hexanoate, ethyl decanoate, butyrolactone, 2-heptenoic acid, and sorbic acid. Based on OPLS-DA analysis, VIP values, and ROAV values, 7 key characteristic flavor compounds were identified, including linalool, 2-octanone, 3-ethylcyclopentanone, 3-octanone, nonanal, 2-pentylfuran, and m-xylene. These results elucidated that Lactobacillus paracasei H4-11 effectively inhibited the growth of spoilage bacteria, mitigated the production of off-flavour compounds, and regulated the flavor profiles, thereby enhancing the overall sensory quality of rice sour soup. This study offered valuable insights into the flavor optimization and spoilage control of fermented foods.