苹果酒融合子综合性能的酵母优选研究

采用原生质体融合技术构建的增香型苹果酒酵母融合子P6、W1、W12、W38和3#菌株,全面研究了其发酵性能、抗逆性、凝聚性和海藻糖积累能力等性能指标,并得到了一株优良的苹果酒酵母融合子,为优质苹果酒的酿造和高品质专用苹果酒活性干酵母(Alcohol-fermention Active Dry Yeast,AADY)的研究和开发提供了理论依据。     

苹果酒发酵条件优化及模型的建立研究

选用原生质体融合技术构建的增香型苹果酒酵母融合子W12,通过3因素5水平二次通用旋转组合设计,选取接种量、pH、发酵温度等对影响苹果酒品质的3个关键因子,分别以苹果酒感官评分、酒精度和残糖量等3个质量指标为因变量,建立了与接种量、初始pH、发酵温度之间的数学关系模型,且各模型均达到极显著水平,为优质苹果酒的研究和开发提供了理论依据。     

优良苹果酒酵母的筛选研究

采用本实验室保藏的10株酵母（P6、P8、P11、P15、P25、W38、W41、W41、W52和W65）为备选菌株,以专用啤酒酵母7^#和 葡萄酒酿酒酵母3^#为对照,通过系统试验,包括试验酵母菌落形态和感官评价、发酵能力比较和发酵所得苹果酒品质的评价,筛选出一株最佳苹果酒酿酒酵母W41,其发酵的原酒酒精度达133.0 mL/L,酒体澄清透明,具有苹果酒的典型风味.     

苹果酒酵母优良固定化载体的筛选

以7#苹果酒酵母为试验材料,系统研究了3种固定化载体海藻酸钙、海藻酸钙-聚乙烯醇和海藻酸钙-壳聚糖固定苹果酒酵母后的物理性能和发酵性能,包括固定化载体的机械强度、通透性、显微结构和固定化酵母的酒精发酵能力、发酵苹果酒理化指标、酒精发酵稳定性,结果表明海藻酸钙-壳聚糖具有良好的机械强度(34.32 g/mm2)和通透性(0.1209),固定化后苹果酒酵母发酵力强,初始发酵的苹果酒酒质好,原酒酒精度达9.8%,残糖和酸度分别仅为2.75 g/L、2.77 g/L,且固定化酵母发酵性能稳定,在连续发酵13批次时,原酒酒精度仍维持在9.1%以上。     

高产谷胱甘肽酿酒酵母选育及保健功能苹果酒开发

苹果酒在生产和储运过程中的褐变严重影响苹果酒品质,而酵母菌的代谢产物谷胱甘肽可以抑制苹果酒的褐变。选用实验室筛选出的一株高产谷胱甘肽(GSH)菌株Y-18为出发菌株,利用紫外诱变和硫酸二乙酯(DES)诱变,用96孔板高通量初筛产GSH菌株,用摇床发酵培养复筛,以发酵力及产GSH能力为指标,复筛出高产GSH的优良苹果酒酵母,并对诱变条件和酵母生产GSH的发酵条件进行研究。经过96孔板高通量筛选出的突变株Y18-20在模拟苹果酒发酵条件的培养基中GSH浓度高达46.8mg/L,单位细胞产GSH能力为8.95 mg/g,是出发菌Y-18的2.18倍。96孔板高通量筛选方法具有节约经济成本、提高筛选效率、缩短选育周期的优势,选育出的优良高产GSH的突变菌株Y18-20,有比较好的发酵特性和遗传稳定性,对生产高谷胱甘肽苹果酒、抑制苹果酒褐变从而提高苹果酒品质具有现实意义。     

混菌发酵对苹果酒香气物质及发酵效率的影响

本文研究通过法尔皮有孢汉生酵母(Hanseniasporavalbyensis)和酵母属酵母(Saccharomycescerevisiae)顺序混菌发酵增加苹果酒的风味酯含量和保证苹果酒发酵的发酵效率。方差分析表明两种酵母接种量及该两种接种量的交互因素对混菌发酵效率有显著性影响;对接种量、苹果汁营养条件进行正交试验确定了一种适宜条件,在该条件下,混和酵母具有法尔皮有孢汉生酵母高产酯能力特性和酵母属酵母高发酵效率特性:在15℃下,发酵时间为31d,发酵完毕时苹果酒中总酯浓度为酵母属酵母发酵苹果酒的1.60倍,残余总糖低于4.0g/L。     

原生质体融合法构建增香型苹果酒酿造酵母的研究

以具有强发酵能力的酿酒酵母1605和产香能力好的苹果酒酵母E2为亲本,通过对原生质体融合条件的研究,得出以下结论:根据两亲本的生长曲线图确定两亲本在制备原生质体时的前培养时间为4h;在酶解温度35℃、蜗牛酶终质量分数为1%的条件下,最佳酶解时间为80min,此时,亲本菌株1605的原生质体形成率和再生率分别为92.4%和29.5%,亲本菌株E2的原生质体形成率和再生率分别为93.5%和30.7%;在60℃时,对亲本菌株1605的原生质体水浴灭活15min,即可完全抑制或钝化其原生质体活性。通过对融合子酿造苹果酒的感官和主要香气成分的分析,利用模糊综合评判法优选出8#菌株,该菌株具有产香能力好、发酵能力强的双亲优点,为优良的增香型苹果酒酵母菌株。     

影响果酒酵母甘油产量主要因素的研究

发酵果酒时,酵母生成甘油的量受多种因素的影响。试验选取6种果酒酵母,研究了酵母菌株(Y1、Y2、Y3、Y4、Y5、Y6)、发酵温度(15℃和20℃)及添加铵态氮源(100 mg/L(NH4)2HPO4与不同剂量的SO2(100mg/L和150 mg/L)对苹果酒中甘油产量的影响。同时研究了这6种酵母发酵不同果汁(苹果汁和梨汁)的甘油产量的不同。试验结果表明:(1)不同酵母发酵苹果酒的甘油含量具有极显著差异(P>0.01),6种酵母于15℃下发酵苹果酒的甘油含量为(4.42±0.02)-(6.18±0.07)g/L;(2)6种酵母于20℃发酵的苹果酒的甘油含量均高于15℃,但Y2甘油产量差异不显著(P2>0.05);(3)添加100 mg/L的(NH4)2HPO4,Y1、Y2、Y3和Y4发酵苹果酒的甘油含量较对照显著增加(P<0.05),Y5与对照相比显著降低(P5<0.05),Y6与对照相比降低不显著(P6=0.312>0.05);(4)与100 mg/L的SO2添加量相比,添加150 mg/L的SO2,Y2和Y4发酵的苹果酒的甘油含量显著增加(P<0.05),Y1、Y3和Y6增加不显著(P>0.05),而Y5显著降低(P5<0.05);(5)梨汁不添加氮源,添加100 mg/L的SO2后接种6种酵母于15℃下发酵梨酒的甘油含量均显著高于同条件下发酵的苹果酒甘油含量(P<0.01),其中以Y2发酵的苹果酒甘油含量最高,Y4最低,而以Y6发酵的梨酒甘油含量最高,Y4最低。     

苹果酒香气成分研究进展

苹果酒是苹果深加工的主要产品之一。香气是苹果酒风味的重要因素。文章中综述了苹果品种、酵母和发酵条件等因素对苹果酒香气形成的研究进展 ,并对今后此方面的研究提出了建议     

酵母对苹果酒酿造品质影响的研究

苹果经榨汁澄清后,分别接种七种果酒酵母,20℃恒温发酵。发酵结束后,对苹果酒进行理化分析和感官评价,评定七种酵母的酿造特征,并观察外加氮源和不同量SO2对酵母及苹果酒理化指标的影响。实验结果表明:在相同试验条件下,7号酵母起酵最慢,4号发酵最快,6号发酵最旺盛。加硫组,整体起酵慢。各种酵母酿造苹果酒的理化指标有所不同,酒的香气、口味和风格也不同。氮源和SO2对七种酵母发酵苹果酒的理化指标影响不显著。     

Beer brewing using a fusant between a sake yeast and a brewer's yeast

Beer brewing using a fusant between a sake yeast (a lysine auxotrophic mutant of sake yeast K-14) and a brewer's yeast (a respiratory-deficient mutant of the top fermentation yeast NCYC1333) was performed to take advantage of the beneficial characteristics of sake yeasts, i.e., the high productivity of esters, high tolerance to ethanol, and high osmotolerance. The fusant (F-32) obtained was different from the parental yeasts regarding, for example, the assimilation of carbon sources and tolerance to ethanol. A brewing trial with the fusant was carried out using a 100-l pilot-scale plant. The fusant fermented wort more rapidly than the parental brewer's yeast. However, the sedimentation capacity of the fusant was relatively low. The beer brewed using the fusant contained more ethanol and esters compared to that brewed using the parental brewer's yeast. The fusant also obtained osmotolerance in the fermentation of maltose and fermented high-gravity wort well.     

Construction of a Magnesium-Enriched Yeast Strain and Study on Distribution of Magnesium in the Cells

The fusant strains ZBF-23, ZBF-65, and ZBF-90 with both higher biomass and higher magnesium content in cells were constructed by protoplast fusion. These three fusant strains were used as the source of genome shuffling from which a magnesium-enriched yeast strain F3-3 with better ability to enrich magnesium was obtained. The enriched magnesium of the shuffled strain F3-3 was about 1.83 and 1.57 times of that of the primary strains ZB-29 and ZB-104, respectively. Under optimal fermentation condition, the biomass and magnesium content of cells reached 16.16 g L^?1 and 14.26 mg g^?1. In the total enriched magnesium which was incorporated into the yeast cells, the organic magnesium was about 95.7%, which was mainly in vacuoles and mitochondria. Nucleic acid and protein in the cells also combined 2.59 and 2.91 mg Mg²⁺ g^?1, respectively. The magnesium-enriched yeast strain which possesses higher ability to accumulate and convert inorganic magnesium salts could be used as a magnesium-fortified food supplement.     

UV INACTIVATION OF E. COLI O157:H7 IN APPLE CIDER: QUALITY, SENSORY AND SHELF-LIFE ANALYSIS

Increasing concern about food safety following contamination of unpasteurized apple cider with Escherichia coli O157:H7 reinforces the need for using the best technologies in apple cider production. Pasteurization of apple cider with ultraviolet irradiation (UV) is a low‐cost alternative to heat pasteurization for small processing operations. UV treatment efficacy applied to raw unpasteurized apple cider was examined through evaluation of physical parameters, exposure time and treatment dosage. A UV light processing system was used to treat apple cider. The apple cider received a calculated average dosage of 8777 µW‐s/cm ² per pass through the system. UV light (at 254.7 nm) was effective in reducing bacteria‐inoculated apple cider by an average of 2.20 logs per pass. In multiple passes, the 5‐log reduction mandated by the Food and Drug Administration was achieved. Sensory analysis yielded no significant differences between the UV‐treated and control apple ciders. Experiments with UV‐treated apple cider indicated a significant extension of product shelf life through inhibition of yeast and mold growth. For low throughput apple cider processing operations, this technology is a viable cost‐effective alternative.     

YEAST VITALITY DURING CIDER FERMENTATION: TWO APPROACHES TO THE MEASUREMENT OF MEMBRANE POTENTIAL

Simulated cider fermentations were carried out using a monoculture of a cider strain of Saccharomyces cerevisiae in a sterile apple juice-based medium. The membrane potential of the yeast was assessed in two different ways: firstly by using the fluorescent dyes oxonol and rhodamine 123 and visualising the yeast with flow cytometry and fluorescent microscopy, and secondly by using the acidification power test. These techniques were used on yeast at various stages of a simulated cider fermentation and also on freshly grown yeast (3 days after inoculation) after the addition of an alcohol mixture similar to that accumulating in mature cider (10% ethanol, 200 ppm propan-1-ol, 32 ppm butan-1-ol, 70 ppm butan-2-ol, 190 ppm amyl alcohol, 17 ppm hexan-1-ol and 260 ppm 2-phenyl ethanol). Little change was observed to the plasma membrane transmembrane potential as indicated by oxonol exclusion over a 4 week fermentation period, but rhodamine 123 staining which indicates mitochondrial membrane potential showed a drastic decline during the first 3 days. The total acidification power index remained almost constant with fermentation age, but the individual components of the index showed considerable changes.     

纳他霉素融合子Sr-1发酵培养基成分优化

本实验根据对融合子Sr-1菌株摇瓶培养基组成及发酵条件单因素优化基础上,利用响应面法获得最佳的培养基配方为葡萄糖33g/L、糊精7.7g/L、胰蛋白胨26g/L、酵母浸粉8.2g/L、初始pH7.0、最佳接种龄28h,发酵周期72h。     

青岛啤酒酵母和高浓酵母原生质体融合选育高浓酿造菌株

以青岛啤酒酵母和高浓酵母为供试菌株,通过原生质体融合得到融合子。对融合子利用铜抗性初筛,利用耐压和发酵性能为指标进行实验室和100 L发酵复筛,并对融合子进行鉴定及遗传稳定性实验。结果表明：通过原生质体融合选育出的高浓菌株与青岛啤酒酵母菌株相比,表现出酵母数峰值高、降糖和还原双乙酰快的优势,且代谢风味物质组成与青岛啤酒酵母接近;经过连续使用8 代后,其总染色体DNA指纹图谱保持一致,证明该菌株的遗传稳定性高。     

甜苹果酒的发酵工艺优化

发酵工艺对苹果酒品质有重要影响.以感官质量为评价指标,以发酵温度、糖度、酸度、接种量为试验因素,进行四因素三水平正交试验,对甜苹果酒主发酵工艺进行优化.甜苹果酒主发酵的最佳工艺条件是:发酵醪调至糖度20°Bx、酸度(按苹果酸计)6g/L,按接种量为0.25g/L接入酵母,在18℃温度下发酵7d,前1～2d对发酵醪进行通...     

原生质体融合构建耐高温酵母菌株

通过原生质体融合选育耐高温的酵母 ,以解决在纤维素类物质同步发酵过程中酵母发酵温度同纤维素酶酶解温度不一致的问题。利用电场诱导原生质体融合技术对产酒率高的菌株Sb1和产酒率低但耐高温的菌株No 30进行融合。经过融合条件的选择 ,分别对 2亲株进行遗传标记 ,3 5 %蜗牛酶处理原生质体 ,在脉冲强度为 11kV、宽度 10 μS、次数为 2次时进行融合 ,得到数株融合子。鉴定得知 ,融合子 2是所需要的融合子 ,其在固态发酵 45℃时产酒精能力达到体积分数 7 2 8%。