The Growth And Decline Of Some Organic Acids During Grape Juice Fermentation

According to OIV(2006), Wine is an alcoholic beverage that is made by fermenting grapesor grape juice, alcoholic concentration of wine should be more than8.5%(volume percent).Organic acid can restrain germ’s activity, and also can dissolve pigment, which makes wine’scolor fresh. Every species of organic acid has special sour, the content of which can influencethe taste of wine.The object initially determined that how to measure yeast’s dry weight、reducing sugar、tartaric acid、actone acid、lactic acid、alcoholic concentration in the process of grape juice’salcoholic fermentation, which were measured by colorimetric method, plotting fermentationparameters’ standard curve, obtaining regression equations, calculating variation of thoseparameters finally.The whole experiment was measuring mutative tendency of fermentation parameters’concentration at different sugar、different temperment and differnet grape species conditions.Analyzing per zymotic fluid according to mutative tendency, we speculate that highfermentation temperature and high sugar content restrain yeast from growing or breeding,then make organic acid and outcome differ.Establishing mathematic model according to fermentation parameters, in other words thatestablish alcohol-fermentation yeast growth kinetics and substrate consumption kineticsthrough the Logistic equation,establish lactic acid and ethanol growth kinetics.Throughnon-linear fitting of yeast’s growth、reducing sugar’s consumption、lacitic acid’s yield andalcohol’s yield by origin software, fitted value of yeast’s growth、 reducing sugar’sconsumption and alcohol’s yield dynamic model was agree with experimental value,andevaluate kinetics parameter was above0.9,but evaluate kinetics parameter of lacitic acid’syield (0.7263～0.8352) was low. Comparing dynamic parameter we obtained, the trend wasagree with the law of ferment.