| The hotbed chives in Puding County,Guizhou Province have less crude fiber,fragrant smell and crisp texture,and the market is in short supply.However,there are phenomena such as broken ends and sharp points in hotbed chives from picking,washing,rinsing,cutting and packaging,which not only wastes resources and pollutes the environment,but also affects the economic benefits of the hotbed chives industry.Through the low salt mixed bacteria fermentation and boiling processing of hotbed chives in Puding County,Guizhou Province,this paper aims to develop low salt,delicious and healthy hotbed chives sauce products.In order to provide a theoretical basis for the processing,manufacturing,popularization and utilization of hotbed chives sauce,the research contents include screening the dominant bacteria,optimizing the preparation strains and fermentation process,comparing the fermentation characteristics of hotbed chives,evaluating the quality of hotbed chives sauce,etc.The results of this paper are as follows:(1)The 16S and ITS high-throughput sequencing technology were used to study the diversity,similarity,species composition and succession of bacteria and fungi of hotbed chives in the process of natural fermentation,so as to clarify the dominant flora of hotbed chives fermentation.12 bacterial genera and 9 fungal genera with relative abundance higher than 1%were detected by natural fermentation of hotbed chives,and fungi were inhibited and decreased in the late stage of fermentation.The dominant flora in the early stage of fermentation included Weissella,Leuconostoc and Cystofilobasidium,and in the later stage,Lactobacillus was the dominant bacterial group.(2)Growth characteristics,antagonism,salt tolerance,acid production characteristics and aroma production effect were used to determine the fermentation characteristics and feasibility of three preliminary bacteria:Lactobacillus plantarum(Lp),Leuconostoc mesenteroides(Lm)and Saccharomycetes.1383(S1383).The comprehensive evaluation method of total acid combined with sensory evaluation were used to optimize the compounding of strains.The results showed that Lp,Lm and S1383had strong fermentation ability and feasibility.They all entered the exponential growth period within 5 h,and entered the stable period at the slowest 26 h,and had strong growth ability without decayed within 36 h.There was no antagonistic effect between strains and had strong tolerance to 0%～6%salt.Lp and Lm had strong acid production capacity,and the p H was reduced from above 5.5 to below 4.0 within 24 h.The S1383 fermentation had a high preference for sensory flavor of 100%,strong aroma production ability,and28 volatile components were detected.In the strain compounding test,the comprehensive score of the mixed compounding of three strains was the highest.When the compounding ratio of Lp,Lm and S1383 was 2:2:1,it was the most conducive to the fermentation of hotbed chives sauce.(3)The response surface test design was used to study the influencing factors such as the addition of mixed bacteria and pickled salt,fermentation time and temperature.The fermentation process of hotbed chives sauce fermented by low salt mixed bacteria was optimized by using Delphi-CRITIC to comprehensively evaluate the indexes such as total acid,p H,total soluble solid(TSS)and fuzzy sensory evaluation.The results showed that the optimum fermentation parameters of low salt mixed bacteria were as follows:the addition of pickled salt was 2.7%(m/m),the addition of mixed bacteria was 2.7%(v/m),the fermentation temperature was 27°C,and the fermentation time was 9 d.Under these conditions,the total acid was 7.81 g/kg,p H was 3.8,TSS was 5.5%,the fuzzy sensory evaluation score was 93.8,and the comprehensive score was 0.99.(4)The main safety physical and chemical indexes,flavor indexes and antioxidant indexes of unfermented hotbed chives,low salt mixed bacteria fermentation and natural fermentation hotbed chives were compared to explore the changes of hotbed chives fermentation.The characteristics of low salt mixed bacteria fermentation process of hotbed chives were as follows:the b~*value(yellowness index)was similar to that of unfermented,which could fully retain the primary color of hotbed chives.The content of amino acid nitrogen was 0.23 g/100g,which was significantly higher than that of unfermented and natural fermentation.The nitrite content was 2.17 mg/kg,and the nitrite peak was 5.65 mg/kg,which was lower than 12.91 mg/kg of natural fermentation.The content of biogenic amine was 40.19～50.11 mg/kg,which was in the safe range.Tryptamine was not detected,and spermine was the main component.Organic acid was8.62～11.96 g/kg,slightly higher than that of natural fermentation.Lactic acid and acetic acid accumulated continuously,which were 5.64 and 3.40 g/kg respectively in the later stage of fermentation.Tartaric acid increased first and then decreased,while oxalic acid,malic acid and citric acid decreased gradually.The volatile flavor component was 1263.99mg/kg,which was about 10 times higher than that of unfermented and natural fermentation.It was mainly sulfide aroma,in which the contents of allyl methyl disulfide and diallyl disulfide were the highest.Flavonoids and polyphenols were 56.43 mg/100g and 107.38 mg/100g,respectively,and there was no significant change in the fermentation process.The DPPH radical scavenging rate was the highest,close to 90%,the hydroxyl radical scavenging rate was about 12%,and the total antioxidant capacity was 22.60μmol/g,which was significantly higher than that of unfermented and natural fermentation.The results showed that the fermentation of hotbed chives by low salt mixed bacteria was safe,retained the original color of hotbed chives,and had better flavor and stronger antioxidant activity.(5)The low salt mixed bacteria fermented hotbed chives were processed by boiling,and the basic nutritional indexes,microbial indexes,texture characteristics and flavor evaluation were comprehensively analyzed,and the effects of three pepper excipients of Chaotian pepper,space pepper and pickled pepper on the quality of hotbed chives sauce were compared.The three pepper excipients hotbed chives sauce had similar nutritional components and texture characteristics,including protein 1.70～2.62 g/100g,fat59.70～75.92 g/100g,salt 1.14～1.48 g/100g,and water 60.04%～65.30%,and no coliform bacteria were detected,and the total number of colonies met the reference standard.The texture was soft and the fluidity was moderate.The sensory flavor grading scores were about 32.00.The electronic nose analyzed two main components,with a cumulative contribution rate of 92%.The flavor components of hotbed chives sauce of Chaotian pepper,space pepper and pickled pepper were greatly different,and 68,67 and 73 volatile components were detected respectively,of which more than 50%were organic sulfur compounds,mainly diallyl disulfide(21%～27%).The relative contents of aldehydes and esters increased.The main flavor contributors were allyl methyl disulfide,dimethyl trisulfide,allyl methyl trisulfide and(E)-3.7-dimethyl-2.6-octadienal.(6)Through the study on the low salt mixed bacteria fermentation technology and boiling processing quality of hotbed chives sauce,the reference standards for low salt mixed bacteria fermentation of hotbed chives sauce are recommended as follows:the sensory requirements should have the color of hotbed chives and pepper,rich and coordinated leek flavor,uniform sauce shape and no foreign matter;moisture≤80.0g/100g;salt≤4.0 g/100g;total acid≤2.0 g/100g;amino acid nitrogen30.1g/100g;coliform group≤10~2 CFU/g.Under this process and standard,hotbed chives sauce fermented by low salt mixed bacteria has the characteristics of salty,sour and delicious,unique style and strong flavor,and has potential advantages in condiments,rice sauce and so on. |
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