【作者】 龙杰；

【导师】 陆健；

【作者基本信息】 江南大学 ， 发酵工程， 2008， 硕士

【摘要】 大麦是啤酒酿造的重要原料之一,占据啤酒原料成本相当重要的一部分。本论文针对部分国产低发芽率大麦溶解性能较差的缺点,利用白地霉提高其溶解性能。在制麦过程中分别接种5株具有高水解酶活的白地霉,均能提高麦芽的溶解,特别是胚乳细胞壁的降解;接种G. candidum JN-4其成品麦芽的溶解指标最佳, G. candidum JN-4液态培养表明:以5oP麦汁为培养基,初始pH值为5.5,接种孢子浓度为2 % ,装液量为50 mL/250 mL,摇床转速为200 r/min,30℃培养40 h,菌体浓度可以达到5×108个/mL的最大值。研究了制麦过程中真菌的变化。在浸麦和发芽阶段,所有的真菌微生物的总量都有明显的增加,发芽最后一天达到最大值。在焙燥阶段,真菌菌群水平下降,但并没有完全消失;制麦过程中添加白地霉能明显改变真菌群落的构成。初步探讨了微生物制麦的作用机制:浸麦初期,白地霉菌株利用接种时的菌体浓度优势,自身吸附到麦芽表面;随着制麦进行,白地霉菌株利用自身的生长优势,占据大麦表面,从而抑制其他微生物的生长代谢。发芽期间,利用自身菌丝体穿透大麦表皮,增强大麦的穿透性,并协助大麦胚乳细胞壁的降解。以G. candidum JN-4为接种微生物,对甘肃省高海拔种植区的低发芽率大麦甘啤3号进行了微生物制麦工艺的研究。结果表明:第1次浸麦时接种104个/g大麦的菌体,提高浸麦水温度至20℃,浸麦方式采用浸5断10浸3断6浸1,发芽采用升温发芽(14℃24 h,16℃24 h,18℃24 h,20℃24 h),焙焦条件为30℃5 h,45℃5 h,50℃4 h ,60℃6 h,70℃2 h,83℃3 h工艺明显促进微生物的作用,微生物麦芽中能反应大麦胚乳细胞壁降解的粗细粉差、粘度和β-葡聚糖3个指标得到明显改善,与对照相比分别下降:10.0 %,22.4 %,36.4 %。更多还原

【Abstract】 Barley was the major raw material used for beer brewing and it was also quite a most important part of the cost. Domestic barley had inferior characterwastics in both germination rate and malt modification. Improving the solubility of low germination rate malt by using Geotrichum candidau microorganism-malting was studied in this paper.Five strains of Geotrichum candida with high extracellular hydrolase were inoculated in the malting process. The results showed that all the strains mentioned above were beneficial to the solubility of malt, especially the degradation of endosperm cell wall. G. candidum JN-4 was chosen as the best for microorganwasm-malting. The optimiziation of condition for spore production was studied. The optimum condition were: the medium was 5 oP wort, the initial pH was 5.5, the spores of inoculation concentration was 2 %, the volume of medium was 50 mL in 250 mL flask, the shaking speed was 200 r/min at 30℃and the culture time was 40 h. The spore yield has been reached 5×108/mL.The changes of fungi contamination during mlating processe were studied. The amount of all fungi increased during the steeping and germination stage, with its maximum on the fianl day of germination, and partly decreased to a certain level at baking stage. Adding Geotrichum candida in malting could change the composition of fungi communities. The mechanism of microorganism-malting was preliminary studied as follows: Geotrichum candida was adsorbed to barley surface firstly due to its high inoculation concentration. Then Geotrichum candida increased rapidly and occupied the barley surface. As a consequence, the growth of other microorganisms was inhibited. During germinating stage, Geotrichum candida penetrated barley surface with its mycelium, which increased penetrability of barley and helped degradation of endosperm cell wall.The microorganism-malting technique had been applied to domestic barley Ganpi-3 which had low germination rate. It was showed that the optimal inoculation concentration of Geotrichum candida spore was 104/g dry barley in the first steeping water at 20℃. Long steeping technology was as follows: 5 hours of water steeping, 10 hours of air rest, 3 hours of water steeping, 6 hours of air rest and 1 hour of water steeping.Calefactive germinationg technology: 14℃24 h,16℃24 h,18℃24 h,20℃24 h and kilning technology: 30℃5 h,45℃5 h,50℃4 h ,60℃6 h,70℃2 h,83℃3 h were adopt. The process could obviously promote effect of Geotrichum candida on barley and especially f/c extract difference, viscosity and 36.4 % which were the index reflecting the degradation of barley endosperm cell wall.Compared with the control,they decreased by 10.0 % , 22.4 % and 36.4 % respectively.更多还原