Study On Fermentation Techniques Of Longan Vinegar And Its Beverage

Longan is a kind of edible and medicinal fruit, it contains many kinds of nutritional components and active substances. Longan vinegar made from Longan juice by liquid fermentation not only has rich nutrition, but also has good health function. Therefore, it has an important developing value.Regarding pectinase addition, temperature and time as effective factors, pectinase hydrolysis was studied by an Ull(l110) uniform design test. The best hydrolysis conditions were that pectinase addition was 0.038%, temperature was at 42℃and hydrolysis time was 4.0h, on condition that the substrate concentration and the pH value kept the same.Angel highly active dry brewing yeast tamed was selected as the breed of alcohol fermentation. Effect of temperature, yeast inocolum size, sugar content, nitrogen resource and pH value on alcohol yield were studied. Alcohol fermentation conditions were optimized, a mathematical model was established and effect analysis was carried out by a quaternary quadratic regression rotational combination design in which alcohol yield was regarded as the index. Results optimized showed that alcohol yield can reach 12.7% by adding an amount of (NH4)2HPO4 with a ratio of TSS:(NH4)2HPO4=900:1 and an amount of 15% yeast breed when temperature was at 30℃, sugar content of Longan juice was 22% and pH value ranged from 4 to 5.A.lovaniense Lacetic acid bacteria tamed was selected as the breed of acetic acid fermentation. Effect of temperature, inocolum size, alcohol content, velocity of the shaking table and pH value on acetic acid yield were studied. Acetic acid fermentation conditions were optimized, a mathematical model was established and effect analysis was carried out by a quaternary quadratic regression rotational combination design in which acetic acid yield was regarded as the index. Results optimized showed that acetic acid yield can reach 6.96g/100mL by adding an amount of 15% acetic acid bacteria breed when temperature was at 33℃, alcohol content was 10%(V/V) and velocity of shaking table was 180r/min.All nutritional components can be better preserved, the appearance quality can be better improved and the transmittance can reach 96.1% when the Longan vinegar was clarified by chitosan. Biological and non-biological turbidity were better solved when ceramic membrane was used to removing bacteria. Ultrafiltration processing was optimized by studying the main factors of pressure, velocity and temperature and results showed that the pressure was 0.14MPa, the velocity was 2.5m/s and the temperature between 25℃and 30℃.The method of fuzzy mathematics comprehensive evaluation was applied in this study, and the model of fuzzy comprehensive evaluation was established. According the results of the fuzzy comprehensive evaluation, the best formula of the Longan vinegar beverage was optimized, and the results showed that the best formula were total acid 0.45%, Longan juice 0.35%, sucralose 0.4‰and fresh Longan essence 0.6‰. Meanwhile, the stability of the vinegar beverage was studied, result showed that the stability preserved under 5℃or 25℃was not changed.