Study On The Acetic Acid Bacteria Breeding And Fermentation Technology Of Jackfruit Vinegar

Jackfruit as a valuable tropical fruit is not only rich in aroma,but also is a high-quality fruit for the production of fruit vinegar.In this study,jackfruit was used as a raw material to brew jackfruit vinegar that meets the relevant national standards and green food standards by breeding the acetic acid bacteria and studying the key enzyme characteristics and jackfruit vinegar fermentation process,which can provide a theoretical basis for the industrial development of jackfruit vinegar.The contents and results of research are as follows.(1)Breeding and identifying acetic acid bacteria for jackfruit vinegar.Based on the results of culturing strains,testing physiology and biochemistry,measuring 16 S r DNA molecular biology and comparing fermentation performance,five strains of acetic acid were isolated and identified from vinegar mash,of which strain Aa941 had the best fermentation performance.After fermenting 96 hours,the maximum acid yield and alcohol-acid transform ratio of Aa941 were 38.70 g/L and 74.85% respectively.It was found the ethanol and temperature tolerance of Aa941 are superior to As1.41,so that Aa941 was selected as the strain for jackfruit vinegar fermentation.(2)The effect of initial acetic acid on the Aa941 and its key enzymes for acid producing.With the initial ethanol concentration in the range of 2.0% to 10.0%,the growth,acid production,enzyme activity of alcohol dehydrogenase(ADH)and aldehyde dehydrogenase(ALDH)of Aa941 increased by the increasing of the initial acetic acid concentration.When the initial acetic acid concentration exceeds 0.5%,the growth,acid production,enzyme activity of ADH and ALDH of Aa941 decreased gradually,and the stable period of growth and acid production was obviously delayed.The transcription level of adh gene of Aa941 was positively correlated with the initial acetic acid concentration and negatively correlated with ADH enzyme activity,but the transcription level of aldh gene was opposite.(3)The effect of initial ethanol on Aa941 and its key enzymes for acid producing.With the initial ethanol concentration in the range of 2.0% to 10.0%,the growth,acid production,enzyme activity of ADH and ALDH of Aa941 increased by the increasing of the initial acetic acid concentration.When the initial ethanol concentration exceeds 4.0%,the growth,acid production,enzyme activity of ADH and ALDH of Aa941 decreasedgradually,and the stable period of growth and acid production was obviously delayed.The transcription level of adh gene of Aa941 was positively correlated with the initial ethanol concentration and negatively correlated with ADH enzyme activity,but the transcription level of aldh gene was opposite.(4)The effect of fermentation temperature on Aa941 and its key enzymes for acid producing.Within 25?37 ? fermentation temperature,the growth,acid production,enzyme activity of ADH and ALDH of Aa941 increased with the rise of fermentation temperature.When the fermentation temperature exceeds 31 ?,the growth,acid production,enzyme activity of ADH and ALDH of Aa941 decreased gradually,and the stable period of growth and acid production was obviously delayed.the transcription level of adh gene and aldh gene of Aa941 were negatively correlated with the fermentation temperature and positively correlated with enzyme activity of ADH and ALDH.(5)Optimizing the fermentation process of jackfruit vinegar.The fermentation process of jackfruit fruit vinegar was optimized by single factor test and response surface design test.Taking Aa941 as the fermentation strain,the best technology of fermented jackfruit fruit vinegar is that 11% inoculation of acetic acid bacteria,fermentation temperature of32 ?,initial alcohol concentration of 5%,and the initial p H of 3.3.Under the above conditions,the acid production is 44.20 ± 0.41 g/L.(6)Analyzing aroma of jackfruit fruit vinegar.68 aroma components of jackfruit vinegar were found by head space-solid phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)and electronic nose analysis technology,including 19esters(32.53%),13 alcohols(17.77%),15 acids(37.02%),1 phenol(0.06%),6 aldehydes(4.36%),3 ketones(0.43%),6 terpenes(0.99%),1 alkane(0.07%)and 4 others(1.06%).The major aroma compounds were acetic acid(26.15%),isoamyl acetate(12.78%),isoamylol(11.01%),ethyl 2-phenylacetate(10.99%),phenylethyl alcohol(4.72%),decanoic acid(3.61%),benzaldehyde(3.34%),phenethyl acetate(3.12%),octanoic acid(3.08%),methyl ether(3.05%),3-methylbutanoic acid(1.31%),ethyl laurate(1.07%).(7)Quality analysis of jackfruit fruit vinegar.By analyzing the quality of the product,the quality index such as sensory,physical and chemical and microbial of jackfruit vinegar meets the requirements of national standards and agricultural industry standards.It has a unique and strong flavor of jackfruit and vinegar,and also has typical characteristics of fermented vinegar.