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China is the biggest country in the world in pear plant, its pear production is far more than that of any other country. Since the harvest of pear is too much to sale in time, processing vinegar by ferment pear can get economic and social benefit. Selenium is one of essential trace element of human. In this paper, the process of yeast enriched inorganic selenium and transformed it into organic selenium was studied. The pear vinegar produced by enriched-selenium yeast ferment can supply not only fruit nutrition but also enough selenium to consumer.Response surface analysis was applied to optimize the fermentation conditions for yeast enriching selenium. Firstly, two-level factorial design of Plackett-Burman was used to evaluate the effect of six related factors on produced biomass and enriched selenium, and four main factors were screened out. Then the path of steepest ascent was taken to approach the optimal region of fermentation conditions, and the optimum levels of four most significantly factors were inoculation volume of 24.9%, Se dosage 18.7 mg / L, culture time 29.4 h, and medium loading rade of 68.8 mL in 250mL flusk. Under the conditions tested, the biomass and selenium content of the yeast were 12.8614 g/L and 2.6593 mg/g respectively. The new good acetobacteria strain of CA1 was separated and the analysis of 16S rDNA sequence indicated that the sequence was similar to the 16S rDNA sequence of Gluconacetobacter diazotrophicus. The strain was able to endure high content selenium, produce more acid and ester, so is an idea strain for produce pear vinegar.The pear vinegar of Suisho was brewed using the solid fermentation. The fermentation condition parameters were optimized by orthogonal test. The optimum conditions for brewing were: inoculation quantity of acetic acid bacteria, 10%;the initial sugar, 12%; ethyl alcohol fermentation time, 5d; the initial concentration of ethanol, 7%; the acetic fermentation time, 10d; pH, 3.2.RP-HPLC was used for analysis organic acids of enriched selenium pear vinegar. Besides acetic acid, malic acid, quinine acid, fumaric acid, citric acid, oxalic acid, succinic acid, lactic acid and tartaric acid were major organic acid in fermented pear vinegar. The kinds and content of orgaric acid were mainly related to vinegar fermentation. Heavy metals and microbial indicators of pear vinegar were determined respectively, the result is: acidity, 5.9%, the 6.05 (mg/100ml) of Ca, 21.77 (mg/100ml) of Mg, 0.21(mg/100ml) of Cu, 4.99 (mg/100ml) of Fe, 19.00 (mg/100ml) of Zn, 1.731μg/100mL (<0.05 mg/kg) of Se, As≤0.04 (mg/100ml), Pb≤0.7 (mg/100ml), bacterium colony total was less than 1400 /ml, Escherichia coli group were less than 3 /100ml, no picked out numbers of pathogenic bacterial. Sensory analysis of fruit vinegar using the fuzzy methodoly, with fuzzy methodology, dealed with data by method of weighted residue, result was accepted easily.
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