The Brewing Of Longan Fruit Vinegar And Its Application

The preparation process of Longan puree, the processing technology of longan fruit vinegar and its application was studied in this paper.During the preparation processing of longan puree, longan can easily change brown due to it contain two special kinds of enzyme-polyphenol oxidase (PPO) and peroxydase (POD). Boiling blanching and steam blanching can inhibit the activity of PPO and POD in Longan. Orthogonal test results showd that the blanching effects of 85℃/5min and 100℃steam /2min were quite good, in which it virtually had no PPO activity and the residual activity of POD was relatively stable, so as to reach the requirements of enzyme inactivation in fruits and vegetables. However, compared 85℃/5min with 100℃steam/2min, the cooked flavor was thicker. combined with sensory evaluation, 100℃steam/2min was considered as the best blanching condition. Adding 0.1% citric acid, 0.1% sodium erythorbate and 0.05% EDTA-Na2 on the browning of longan had not only good inhibition and good product color, but also had little negative impact on the flavor of longan. It was the ideal longan browning inhibitor combination.In the hydrolysis process of Longan pulp, the result showed that the optimum conditions were pectinase usage 0.05% and cellulase usage 0.10%, temperature 45℃, hydrolysis time 90min respectively. Afer enzymatic hydrolysis, Longan pulp combined vacuum with high shear processing to attain enzyme reaction solution of longan flesh. Then longan puree could be obtained through filling steriliazation with enzyme reation solution.The preparation technics of longan fermentation vinegar with longan puree was determined. Firstly, single factor and orthogonal test were designed to study the effects of sugar content, fermentation temperature, inoculum size and initial pH on alcohol content. The result showed that the optimum conditions were sugar content 20%, fermentation temperature 30℃, inoculun size 8% and initial pH 4.5 respectively. we obtained alcohol content up to 11.4% with this optimum combination after experimental verification. Furthermore, we studied various factors on the impact of acetic acid content in the process of acetic fermentation, in which we obtain high content of acetic acid, when the carbon and nitrogen ratio (glucose: yeast extract+peptone) was 1:4. Through single factor and orthogonal test, the optimum conditions for acetic fermentation were fermentation temperature 35℃, alcohol content 8%, ventilation 1:4, inoculum size 8% respectively. We obtained acetic acid content up to 5.64g/100mL with this optimum combination after experimental verification.Finally, based on the use of longan vinegar and longan puree, we developed into the longan fruit vinegar beverage adding honey, sugar and organic acids as accessory materials. Through single factor and orthogonal test, the optimum ratio of raw materials were longan vinegar 8g/100mL, longan pulp 10%, organic acids (citric acid: malic acid = 2:1) 0.20%,sugar 6%, honey 6% respectively. We obtained sensory score up to 94 points with this optimum combination after experimental verification.