Study On Processing And Flavor Components Of Pleurotus Eryngii Sauce Fermented By Lactic Acid Bacteria

In recent years,the industrial cultivation of Pleurotus eryngii has obtained a rapid development and the yield increased significantly.The output was more than 1.1 million tons in 2015.The proportion of processing is less than 10%and the products type of Pleurotus eryngii is relatively simple.The economic benefits continue to decline because of the price advantages disappearing.In order to improve the comprehensive utilization value of Pleurotus eryngii,to develope the processing products which are beneficial to digestion and intestinal health,the fresh Pleurotus eryngii was chosen as material.Through comparing the fermentation properties of different lactic acid bacteria to screen excellent bacterial strains to ferment fresh Pleurotus eryngii.And optimized the process parameters of mixed strain fermentation were studied.Combining the analysis of the flavor substances and sensory evaluation,we developed a kind of Pleurotus eryngii sauce with a thick and uniform appearance,milk-white color,and delicious taste.The research provides a theoretical and technical basis for the Pleurotus eryngii sauce development.The study obtained the following results:?1?Through determining OD₆₀₀ value,pH and titratable acidity production of the culture medium of Pleurotus eryngii juice inoculated lactic acid bacteria,comparing the growth status of each strain in different salt concentration media and different fermentation temperatures.We chose 3 excellent strains with higher growth speed,which has strong ability of producing acid substance,salt and heat resistance to be the suitable strains as the fermentation agent of Pleurotus eryngii sauce.They are from Lactobacillus plantarum,Lactobacillus brevis,Weissella cibaria,Lactobacillus fermentum,and Leuconostoc mesenteroides.The compounding test determined the suitable proportion of 3 strains for 3:2:1.The strains at suitable proportion has stronger acid production ability and protein degradation ability,and the quality of the fermented product is better.?2?The effects of Inoculation amount,salt addition amount,sugar addition amount and fermentation temperature on acid production and free amino acid content of Pleurotus eryngii sauce are analyzed through single factor experiment.By response surface experiment results,the optimum fermentation conditions is that inoculum amount 4.5%?v/m?,the salinity4.1g/100g,fermentation temperature 36?.At these conditions,the titratable acidity content reaches 0.759g/100g.Under the optimal conditions,the titratable acidity content in the verification test is 0.754±0.054g/100g,the model can be used to analyze and predict the content of titratable acidity.And the primary factors affecting the titratable acidity content of the product are inoculation amount,fermentation temperature and salt addition.?3?The organic acids and nucleotides in the Pleurotus eryngii pulp before and after sterilization,the jame fermented by nature and mixed strains respectively were analyzed by HPLC.Amino acids components were determined by amino acid Analyzer.SPME-GC-MS were applied to detect the volatile flavor compounds in Pleurotus eryngii sauce.Results showed that high-temperature sterilization caused a serious loss of flavor substances in Pleurotus eryngii sauce.After fermentation,the content of organic acids were obviously increased,and the main flavor was lactic acid.The content and composition of organic acids in sauce fermented by mixed bacteria were obviously better than the natural fermentation,and the flavor substances were more abundant.Mixed bacteria fermentation increases nucleotide content,otherwise,natural fermentation increased the CMP content,but the IMP content decreased significantly,and the AMP and GMP were not detected.The flavor substances produced by the mixed bacteria fermentation are mainly alcohols,acids,aldehydes and ketones.The natural fermentation are mainly alcohols and esters,and the total content is lower than the mixed bacteria fermentation.The flavor amino acid content decreases,and glutamic acid decreases from 0.126g/100g to 0.045g/100g.Combining the sensory evaluation,the taste and texture of Pleurotus eryngii sauce obtained by mixed bacteria fermentation is superior to natural fermentation.