| Blueberry is a kind of berries rich in nutrition, anthocyanin, and all kinds of trace elements, and has higher edible and medicinal value. Blueberry has been planted a lot currently, but it’s difficult to save the blueverry for a long time after being picked. Few portion of blueberries is eated directly as fresh fruits, while most of them are freezed to preserve for further process. Blueberry wine fermentation is one kind of important further processing methods, and blueberry wine is becoming more and more favorable by the public for its special taste, powerful function and rich nutrition. For better development of blueberry resources, this study researched systematically the characteristics of blueberry wine natural fermentation, the blueberry wine fermentation kinetics, blueberry wine fermentation process optimization, and the change of organic acids in the fermentation process and its effect on fermentation, improved the blueberry wine yeast by using genetic engineering methods, soloved the problem of the inhibition of the wine production from high citric acid content in fruit juice. The tested blueberries-Lan feng, Berkeley, Sheng yun, Bei qing, Bei lu, were sampled in Liaoning province.The results were as follows:1. Fermented naturally five kinds of blueberries, the results showed that the biggest weight reduction of CO2 of "Lan feng " is 0.74g in the experiment condition. Moreover, it was proved that " Lan feng " yeast grew most fast comparing with the other four kinds of blueberries, reduced sugar and produced wine quickly through the growth curve, hypoglycemic properties, determination of wine production capacity, as well as conductivity and dissolved oxygen changes during the fermentation. Further studies dynamics of the varieties of fermentation showed that the dynamic changes of the fermentation process can be predicted well. During fermentation, the strain growth rate was similar (except the yeast growth of "Bei qing" was slow). Alcohol generation, Lan feng>Berkeley>Bei lu>Sheng yun>Bei qing. The substrate consumption rate, Lan feng>Berkeley>Sheng yun>Bei qing>Bei lu. Then the best yeast of the natural fermented blueberry wine was identified, and blueberry wine fermentation kinetics was fited which provided the theoretical basis for blueberry wine natural fermentation production.2. The dynamic models of bacteria growth, alcohol production and sugar consumption were established through analysis and study on the dynamics of alcohol fermentation process. The decision coefficients of three models were 0.991,0.985,0.979, respectively according to the results of variance analysis, so the dynamic change of fermentation process can be well predicted by the models. The strain growth rate, alcohol generating rate and the substrate consumption rate during the blueberry wine fermentation process were calculated through solving the first derivative of the fermentation kinetics equation to know more clearly about the blueberry wine fermentation process.3. The optimum parameters of blueberry wine fermentation were tested through the center combination of response surface design, such as enzyme addition quantity of 0.13 ‰, temperature of 22.0℃, the inoculum amount of 1.63‰. The wine production was 11.8% vol in this condition. The best process condition of three factors of affecting the amount including enzyme addition quantity, fermentation temperature, inoculation amount (enzymatic) was studied, and the results showed that three factors influenced the amount of alcohol significantly, and the order of their importance is, temperature>inoculation quantity> amount of enzyme. The alcohol content of validation test samples was 11.823% vol, similar to that of forecast, which can verify the reliability of the model.4. Organic acids change of fermentation and its effect on fermentationThe total acid amount increased with the increase of sucrose and fructose addition amount, while decreased with the increase of the glucose addition amount. The trend of pH value changing with the sucrose, fructose,and glucose was opposite to that of the total acid.As sucrose content increased gradually, oxalate and acetic content reduced firstly and then increased, citric acid content gradually reduced; With fructose content increased, the oxalic acid content increased firstly and then smoothed. As the glucose content increased gradually, oxalic acid content decreased firstly and then increased, citric acid reduced gradually, which indicated that addition of glucose to the transformation was helpful for the transformation of citric acid in the blueberry wine.With the increase of organic acid concentration, PDC enzyme activity decreased gradually, and approached zero when the content of citric acid was 14.5 mg/mL. While the effects of oxalic acid and acetic acid on PDC was relatively small. With the increase of organic acid, enzyme activity decreased slowly.With the increase of organic acid concentration, AHD enzyme activity decreased gradually, approached zero when the content of citric acid was 25 mg/mL.While the e effects of oxalic acid and acetic acid on AHD was relatively small. With the increase of organic acid enzyme activity decreased slowly.5.The citrate lyase gene of aspergillus fumigatus was imported into saccharomyces cerevisiae by using genetic engeering methods. Then the citrate lyase was separated and its biological characteristics was detected after expression. Also improved strain fermentation characteristic of blueberry wine was verified through further fermentation test. Finally, by compairing the datas, we can get the result that the new improved strain can degradate sugar and producte alcohol faster, with shorter fermentation period... |
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