Selection Of Excellent Lactic Acid Bacteria And Its Application In Vegetable Fermentation

Fermented vegetables have a long history and inoculated fermentation is accepted for its criterion, security and criterion. The pattern of fermented vegetables is changing from traditional spontaneous fermentation to inoculation fermentation nowadays and strains are the key reason for rapid, stable and high-quality fermentation. In this study, lactic acid bacteria with excellent characteristics of fermentation and antimicrobial activities were selected, and its application in cucumber fermentation was optimized through response surface methodology (RSM). The results of this research are of great importance in accelerating the industrialized, scaled and standardized fermentation model as well as improving the quality and shelf life of fermented vegetables.In this study, Lactobacillus acidophilus, Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus fermentum were resistant to Proteus vulgaris, Aspergillus niger, Escherichia coli and Staphylococcus aureus. Taking their inhibition zone into consideration, combination of L. helveticus and L. acidophilus (with a proportion of1:1) was chosen as the starter culture. Based on single factor experiments, RSM was conducted and the optimum values for the variables were inoculation size4.15%, salt3.85%, sucrose0.99%, respectively. Under this condition, the predicted titratable acidity reach0.7748%, nitrite content0.1318mg/kg, final salinity2.914%and the value of sensory evaluation3.846. After verification, the condition was valid for increasing the quality of pickled cucumber, proving that RSM is feasible for optimizing the fermentation process.Cucumbers were fermented by spontaneous and inoculating ways and it was concluded that inoculating lactic acid bacteria is beneficial for keeping the cucumber original structure intact and organic acids accumulation. In this way, we have investigated the mechanism for lactic acid bacteria promoting the quality of pickled cucumber from both macroscopic and microscopic.Excellent strains selected were used for broccoli fermentation. The results was that inoculated fermented broccoli were superior to natural fermented broccoli in all aspects, demonstrating that starters combined L. helveticus and L. acidophilus with a proportion of1:1improved the quality of the product remarkably. The nutritious pickled product met the requirements of low salinity, low nitrite content and high firmness, which opened up a new way for the development and utilization of broccoli.