Screening of dominant lactic acid fermentation strains, identification and effect on flavor quality of fermented radish

Abstract

[Objective] This study aimed to screen the excellent lactic acid bacteria strains to construct a special pickle fermentation strain for radish. [Methods] Lactic acid bacteria were isolated from the pickle brines of Laotan sauerkraut collected from different regions by dilution coating method. The species were determined by physiological identification, morphological identification （colony observation, Gram staining）, 16S rDNA gene sequencing and phylogenetic tree construction, and their growth characteristics, tolerance and flavor substances were detected. [Results] Isolation, screening, and physiological identification yielded 120 colonies of round, convex bacteria, which appeared rod-shaped or spherical under the microscope and were all Gram-positive strains. Further 15 strains with high acid production capacity were obtained by acid production capacity test. By molecular sequencing, 1 strain was identified as Bacillus, 13 strains as Lactobacillus plantarum and 1 strain as Pediococcus pentosus. Among them, L. plantarum was the dominant lactic acid fermentation strain screened in Sichuan, Chongqing, Liaoning, Guizhou, Hunan and Nanping of Hubei province, and Bacillus and P. pentosus were screened in Tuanbao area of northern Hubei Province. The growth characteristics of different types of fermentation strains were analyzed, and the growth rate of strains LA-8 and LA-11 was faster than other strains; Strain LA-8 had the highest acid production capacity, and was resistant to 10% salt and 15% sucrose. All four strains had the ability to degrade nitrite. Strains LA-4 and LA-6 were able to produce 15% sucrose, and their growth rate and acid-producing capacity were slightly lower than that of L. plantarum. The initial experiment of radish fermentation showed that LA-8 and LA-11 had stronger fermentation ability and faster acid production. The electronic nose detection technology was used to detect the fermentation flavor of radish, and it was found that the volatile substances produced by four strains of different types of lactic acid bacteria were different. [Conclusion] Three different types of dominant fermentation strains were screened from the mother water of radish laotan pickle in different regions, which could be further used as the source of strains for the production of radish pickle industry.

Keywords

• old jar pickles
• lactic acid bacteria
• fermentation
• screening
• identification