Identification Of Microorganisms From Ripening Zhacai And Research On Starter Cultures For Zhacai Processes

This research takes the natural fermentation process of quality zhacai as investgating object, by measuring and analyzing the separation, cultivation, calculation and classification of microorganisms and gross acidity, amino and nitrogen during different fermentation periods, the paper tends to exploit the bacteria form, the changing principle of the bacteria family and the major microorganisms in zhacai ferment system. Based on tendency analysis on traditional zhacai spontaneous fermentation, the paper should study the major microorganisms and their performance in zhacai production, choose bacteria vaccine and its addition, improve preparation and fermentation technique of zhaicai production, thus provide theoretical basis for development of suitable preparatory culture of zhaicai production. The conclusions are as followed:1. Pedicoccus acidilactici, Pedicoccus halophilus, Streptococcus faecalis, Streptococcus lactis, Leuconostoc mesenteriodies, Bacillus subtilis, Bacillus cereus, Bacillus sphaericus, Bacillus polymyxa, Bacillus stearothermophilus, Bacillus firmus, Lactobacillus plantarum, Lactobacillus.halotolerans, Lactobacillus fermentum, Lactobacillus lactis were selected for production of natural fermented zhacai2. Saccharomyces rouxii, Saccharomyces globosus, Saccharomyces cerevisiae, Rhodotorula minuta, Torulopsis versatilis, Debaryomyces hansenii, Hansenula anomala were selected for production of natural fermented zhacai3. Penicillium spp, Aspergillus spp were selected for production of natural fermented zhacai4. More than half of isolating microorganisms were lactic acid bacteria. Lactic acid bacteria lactic acid fermentation is important during zhcai after ripening and fermentation. Lactic acid bacteria produce lactic acid from hexoses. The zhacai end-products of carbohydrate catabolism by lactic acid bacteria contribute to the flavour, aroma and texture, thereby helping to determine unique product characteristics. For instance, the synergistic effect of Pedicoccus halophilus and Saccharomyces roiai has been investigated in detail due to its pivotal role in allowing growth in the development of flavour and texture in zhacai.5. The main purpose of this study was to obtain starter cultures for zhacai marking process. Lactic acid bacteria strains were isolated and identified. The metabolic properties (growth rate, acid producing ability, temperature resistance and salinity tolerance) of the selected strains were determined. The strains with best potential as zhacai starter culture were Lactobacillus plantation, Leuconostoc mesenteroides and Lactobacillus lactis. To get a better fermentation technology, the three kinds of bacteria were used as fermentation strains, with different inoculation amount, inoculation for ratio, salinity, water content and vacuity in an orthogonal experimental design and sensory evaluation test. A sequence that indicates the importance of different factors was got, that is, strains ratio > salinity > water content > vacuity. Moreover, a ideal starter culture combination was gained, that is, inoculation amount 3%, the ratio of Lm:La:Lp = 3:1:1, water content 80%, salinity 6% and vacuity 0.091Mpa. In the sensory evaluation test, the quality of zhacai produced with this starter culture has no significant differences with natural fermentation zhacai, as well as their acceptance. Measuring of pH and acid-forming performance results show that artificial inoculation can induced the 180 days fermentation period of traditional fermentation to 20 days, The formation of flavor compounds takes about 60 days, with the same acid-forming amount, and shorten the fermentation period to 1/3 of original fermentation period.6. The change rules of sensory indexes and physiochemical indexes for artificial inoculation and natural fermentation during zhacai fermentation were studied. The results indicated that artificial inoculation was identical in sensory indexes and physiochemical indexes in relation to natural fermentation, while artificial inoculation was more effective in retaining amino acid nitrogen and protein content of zhacai than natural fermentation. Artificial inoculation also could significantly reduce the nitrite content of zhacai, enhance the safety of zhacai production, artificial inoculation could accelerate the process of zhacai after ripening and fermentation, pick up the development of flavour and texture, shorten the generating period of zhacai production, had little effect on sensory quality. Artificial inoculation is a feasible approach for zhacai actual production.