【作者】 张明霞；

【导师】 岳田利；

【作者基本信息】 西北农林科技大学 ， 食品科学， 2003， 硕士

【摘要】 固定化酵母发酵，便于产物分离，易于实现连续化发酵。为进一步推进猕猴桃酒的连续化生产，本课题进行了猕猴桃酵母固定化技术的研究。 试验首先确定2／3麦芽汁+1／3果汁为猕猴桃酵母扩大培养基，筛选出猕猴桃酵母1450作为固定化酵母。 试验对猕猴桃酵母1450的固定化方法和材料进行了研究。所用载体材料为海藻酸钠和海藻酸钠与聚乙烯醇组成的复合材料。分别对他们的固定化条件进行研究，以凝胶形状、相对扩散系数、柠檬酸钠溶解时间、包埋菌量作为分析指标，确定海藻酸钠载体的交联剂为4％CaCL₂，载体浓度为2.5％；复合材料载体的交联剂为4％CaCL₂，载体的配比为2％海藻酸钠+6％聚乙烯醇。 通过发酵能力、使用寿命、贮存稳定性和电镜扫描观察的比较，确立了2％海藻酸钠+6％聚乙烯醇组合的复合材料B为固定化载体。复合材料B制备的凝胶发酵速度为90g／L·d；使用15批后包埋菌数下降了1.2％；贮存36天后，包埋菌数下降了16.7％；电镜扫描内部结构较为疏松，适宜微生物的生长和繁殖。 利用单因素分析，分别研究温度、pH、起始糖度和填充量对固定化酵母发酵的影响，温度低于22℃时，发酵速度和转化率随温度的升高而增大，高于22℃后，温度越高反而抑制固定化酵母的发酵；pH低于3.5时随pH的增大发酵速度加快、残糖量降低，高于3.5后，由于杂菌的影响发酵速度反而减慢、残糖量升高；起始糖度低于250g／L时发酵速度随起始糖度的增加而加快，尤其是在150g／L～250g／较为显著，高于250g／L时由于底物浓度过高，渗透压较大，抑制固定化酵母的发酵，发酵速度减慢；填充量低于0.4g／mL酒精度高，发酵速度慢，大于0.4g／mL酒精度低，发酵速度快。确定发酵最佳的温度为22℃、pH3.3、起始糖度为250g／L、填充量为0.48／mL。利用正交试验分析找出发酵条件的组合为温度25℃、pH3.3、起始糖度270g／L、填充量为0.4g／mL。在此条件下固定化酵母的发酵速度是游离酵母的3倍，酒精度增加1.5被，酒中的Vc保存率为68％ 固定化猕猴酵母发酵猕猴桃果汁，发酵周期为3天，其酒中总算含量为8.048g／L，挥发酸含量为0.31g／L酒精度达到16％v／v，V_C保存率达到68％，透光率为83.6％；酒的色泽为淡黄色，晶莹透亮，果香味浓郁，酒体丰满圆润。更多还原

【Abstract】 To immobilize the fermentation of yeast improves the separation of products from the ontology and realizes successive fermentation. In this paper, the immobilization of kiwifruit wine yeast was studied.2/3 malt juice and 1/3 juice were selected as the growth mediu for kiwifruit yeast to sieve kiwifruit yeast 1450 as the immobilized yeast.The techniques and materials of immobilization of kiwifruit yeast 1450 were studied in the experiments. The experiments selected sodium alginate and the composite of sodium alginate and polyvinyl alcohol as carriers and studied their immobilization conditions, taking the shape of bead, the coefficient of relative expansion, the dissolving time of sodium lemon and strains contained as analytical targets. The cross linking agent of carrier sodium alginate was determined as 0.2 MCaCL2, its density 2.5%; while that of the composite was 4%CaCL2, and its components were 2% sodium alginate and 6% PVA.In contrast with the fermentation abilities, the time for use, the stabilities for storage and the results through the observation of the electron micrograph scanning, the composite of 2% sodium alginate and 6% PVA was determined as the immobilized carrier. The fermentation speed of the bead from this composite was 90g/L.d; afterlS times of using, the strains dropped at 1. 2% and after 36 days of storing, the strains dropped at 16.7%. The electron micrograph showed their inner structure became looser, which was favorable for the growth and multiplication of the microorganism.Analyzes of the impacts of temperature, pH, initial sugar content, and fillings on the fermentation of the immobilized yeast suggested the following facts.The fermentation speed and conversion rate increases with the increase of the temperature when the temperature is below 22℃ while above 22℃,the fermentation was restrained. The fermentation speed increased and the sugar content drops with the increase of pH when pH is below 3.5 and the reverse comes true when pH is above 3.5 owing to the influence of the miscellaneous bacteria. The fermentation speed increases with the increase of the sugar content when the initial sugar content is below250g/L, especially between 150g/L-250g/L while when the initial sugar content is above 250g/l, the fermentation speed drops because the higher osmotic pressure by higher density restrains the fermentation of the immobilized yeast; and the fermentation speed keeps slower and the spirit content keeps higher when fillings are below 0.4g/mL while above 0.4g/mL, come the reverse. Through the experiments, the optimum temperature, pH, the initial sugar degree and the fillings were concluded as 22℃, 3.3, 250g/L, and 0.4g/ml respectively. In this condition, the fermentation speed of the immobilized yeast is three times as fast as that of the free yeast and the spirit content increases by 0.5 time, among which 68 percent Vc is preserved.The fermentation cycle covers three days by applying immobilized kiwifruit yeast into fermenting kiwifruit juice. In the wine, the total acid amounts to 8.048 g/L, the volatile acid 0.31 g/L, the alcohol degree 16% v/v, the Vc preserved 68%, and the transparency 83.6%. The wine appears light-yellow and crystal, smells fragrant, and tastes smooth.更多还原