Abstract: Heat treatment is often used to inhibit microbial growth in Pixian chili sauce for extending its shelf-life, but some microorganisms are still likely to survive, causing Pixian Chili Sauce to spoil during storage. In this study, Pixian chili sauce treated at 80℃ for 30 min was enumerated for total aerobic bacteria, coliforms, moulds and yeasts during storage at room temperature for 120 days. Bacterial and fungal strains isolated from chili sauce were identified by 16S rDNA and ITS sequence analysis respectively, and PCR-DGGE technique was used to analyze the bacterial community at the end of the storage period. The total number of bacteria in chili sauce decreased more than 90% after heat treatment at 80 ℃ for 30 min, and the majority of surviving microbes were Bacillus sp. During the storage period of 120 days, the total number of bacteria in heat treated chili sauce increased at first and then decreased. The dominant surviving bacteria in chili sauce at the end of the storage period, as detected by PCR-DGGE, were Pediococcus sp., Lactobacillus sp. and Bacillus cereus. These results demonstrate that partial microorganisms in chili sauce are killed or presented in VBNC (viable but non-culturable) state after heat treatment, and surviving Bacillus sp. and lactic acid bacteria may be the reason for the spoilage of heat-treated chili sauce. Consequently, effectively controlling the survival Bacillus sp. and lactic acid bacteria is the key to extend the shelf-life of chili sauce.

Key words: heat treatment, shelf-life, aerobic bacteria count, PCR-DGGE, viable but non-culturable (VBNC)