酵母提前絮凝的研究进展

介绍了国内外关于酵母提前絮凝的研究进展及导致酵母提前凝的因素和酵母提前絮凝的假说机理,归纳了酵母絮凝的检测方法,提出了预防酵母提前絮凝的措施及酵母提前絮凝的研究方向。     

啤酒酵母絮凝性的讨论

本文从啤酒酵母的絮凝特性及主要影响因素，分析了啤酒酵母絮凝性对啤酒生产过程及啤酒质量的影响，介绍了啤酒酵母絮凝性的测定方法。     

啤酒酵母絮凝机理研究进展

啤酒酵母絮凝机理的假说有絮凝共生假说、类外源凝集素假说、类外源絮凝素假说等。啤酒酵母絮凝表型可分为FLO1型和NewFLO型;对啤酒酵母絮凝基因的研究有结构基因——见O基因家族、调节基因及其他相关絮凝基因。对啤酒酵母絮凝性状的改良研究可应用于调控啤酒酵母絮凝性状,利于啤酒生产;利用酵母絮凝性状构建絮凝选择栽体;利用絮凝素蛋白构建酵母细胞表层展示体系;利用酵母絮凝蛋白对细菌的吸附,应用于医疗行业。     

快速发酵法测定麦芽引起酵母提前絮凝(PYF)的方法建立与应用

麦汁成分变化可能引起酵母的过早凝聚（premature yeast floeculation，PYF）。本文根据Lager酵母特性及生产工艺，建立了快速发酵测定麦芽对酵母提前凝聚性值的方法，该法简便、快速、实用。     

利用大麦预测酵母提前絮凝现象的研究

介绍了一种用比色法来判断酵母提前絮凝现象的方法,该方法仅通过测定酵母细胞悬浮液中细胞的沉降速率来判断酵母絮凝性,无需制麦、发酵,只需简单的提取操作即可进行,克服了发酵力试验的一些缺陷。通过正交实验优化了大麦中絮凝因子的提取工艺,研究了不同菌种对大麦絮凝因子的敏感程度。通过与啤酒大生产所反映的实际情况做对照,该方法预测的结果与实际大生产有很强的对应性。     

影响啤酒酵母絮凝的外部因素探讨

介绍了啤酒酵母絮凝性在啤酒生产中的重要意义，论述了营养因素、温度与pH值、酒精浓度、菌种传种代数、酵母接种量、原料、通风溶氧状况以及卫生条件控制等诸多外部环境因素对啤酒酵母絮凝的影响。     

麦芽中超前絮凝因子多糖的提取与性质研究

啤酒发酵中的超前絮凝现象（PYF,premature yeast flocculation）主要由麦芽中的多糖引起。本文将麦芽汁进行醇沉、Sevag去蛋白、超滤、DEAE-Sephadex A-25及Sephadex G-100柱层析等一系列分离,提取得到一种分子量在10000Da以上的多糖物质PYFⅠ-Ⅰ,酵母超前絮凝活力测定及聚集沉淀后的酵母形态均能证实该多糖能显著促进酵母絮凝。对其性质进行研究发现,该多糖为糖蛋白,糖含量和蛋白质含量分别为58.3%、3.8%。这种多糖物质的发现为进一步研究啤酒发酵中的PYF现象奠定了基础。      

麦芽中超前絮凝因子多糖的提取与性质研究

啤酒发酵中的超前絮凝现象(PYF,premature yeast flocculation)主要由麦芽中的多糖引起.本文将麦芽汁进行醇沉、Sevag去蛋白、超滤、DEAE-Sephadex A-25及Sephadex G-100柱层析等一系列分离,提取得到一种分子量在10000Da以上的多糖物质PYF H,酵母超前絮凝活力测定及聚集沉淀后的酵母形态均能证实该多糖能显著促进酵母絮凝.对其性质进行研究发现,该多糖为糖蛋白,糖含量和蛋白质含量分别为58.3%、3.8%.这种多糖物质的发现为进一步研究啤酒发酵中的PYF现象奠定了基础.     

啤酒酵母超前絮凝现象的研究进展

啤酒发酵过程中,发酵液中麦汁等营养物质尚且充足时,酵母已经开始出现凝集沉降的现象,这种酵母过早沉降的现象称之为酵母超前絮凝(Premature Yeast Flocculation)。本文对酵母超前絮凝产生的原因,影响因素,检测方法及预防措施进行了一定的总结,并提出在预防PYF现象的微生物控制指标上有待进一步研究。     

采取工艺措施提高啤酒酵母的絮凝性

啤酒酵母按凝絮性可分为粉末型酵母、凝聚性酵母和絮凝性酵母。絮凝性酵母是目前啤酒酿造中用于快速发酵制造清爽型啤酒常采用的酵母。影响啤酒酵母絮凝性的因素有很多,本文探讨的是如何利用工艺条件来提高啤酒酵母的絮凝性。1 问题的提出我工厂在生产过程中发现有的发酵液降温储酒后,大量酵母仍悬浮在酒液中,沉降效果不好,导致酵母自溶,嫩啤酒浊度高达30EBC 以上,过滤困难,清酒回滤率高,严重影响了过滤效率和过滤清酒质量,为解决这一问题,我们从工艺方面进行了一系列     

麦芽霉菌污染引发啤酒酵母提前絮凝现象的研究

大麦在制麦过程主要的污染霉菌为镰刀霉、烟曲霉和根霉.小试制麦的植菌试验表明,霉菌污染量在102个/g麦芽,PYF平均值为84.3%;霉菌污染量在103个/g麦芽,PYF平均值为70.7%,都会引发PYF;霉菌污染量在104个/g麦芽,PYF平均值为107.8%,不会引发PYF;镰刀霉和根霉的影响大于烟曲霉的影响.     

啤酒酵母凝集性的探讨

从啤酒酵母的凝集特性、作用机理及主要影响因素,分析了啤酒酵母凝集性对啤酒生产工艺过程及啤酒质量的影响,介绍了啤酒酵母凝集性的测定方法.     

Optimization of a Small‐scale Fermentation Test to Predict the Premature Yeast Flocculation Potential of Malts

Rapid and early detection of malts likely to cause premature yeast flocculation (PYF) is of major importance both to the brewer and the maltster. To date, the most reliable and widely applied diagnostic tests for predicting the PYF status of malts involve conducting a small scale fermentation test, which usually takes several days to be completed. This study investigated the impact of selected factors on the ability of such a test to distinguish between PYF positive and PYF negative malts and the fermentation time after which the test results, and therefore the PYF status of the malts, could be confirmed. The results obtained suggest that the PYF potential of malts could be predicted 40 hours post pitching by adding 6 mg.L^?1 linoleic acid and using a highly flocculent PYF sensitive yeast strain.     

麦芽PYF因子活力评价及其与酵母絮凝联系研究

通过考察标准培养基下动态培养下面絮凝啤酒酵母的生长进程、酵母悬浮液初始浓度和用量、缓冲液pH、体系水质、PYF因子提取方式等多因素对测定结果的影响,确立了麦芽PYF因子活力测定体系的最佳参数。麦芽PYF因子加和性及其与酵母絮凝性能关系的进一步分析结果表明:PYF因子具有很好的加和性,对酵母絮凝起促进作用。     

啤酒酵母絮凝影响因素及改善途径的研究概况

啤酒酵母的絮凝性对啤酒生产具有重要意义,不仅影响啤酒的发酵过程也会影响啤酒口感和风味。对啤酒酵母絮凝的国内外最新研究进展和成果进行综述,包括絮凝机理假说,影响絮凝因素,酵母絮凝对啤酒品质和风味影响,改善絮凝途径,期望解决实际啤酒工业生产中酵母异常絮凝出现的一系列问题。     

Modelling of Yeast in Suspension During Malt Fermentation Assays

Premature yeast flocculation (PYF) is a poorly understood condition leading to attenuation of fermentation and poor alcohol yields. The yeast in suspension in fermenting worts prepared from either normal or premature flocculating malts was continually measured during the small 15 mL fermentation test recently developed in the Dalhousie laboratories. A simple inexpensive monitoring system was constructed from a laser level, photometric cell and data logger. This system allowed non‐destructive data collection of absorbance data (over 700 data points per fermentation) at ?650 nm. A non‐linear modeling technique was applied to the data, and yielded two best‐fitting logistic models. The model parameters were quantitatively compared to determine if statistical differences between PYF and normal wort were apparent. A student's t test of the logistic parameters indicated a significant difference (p > 0.025) between control and PYF worts for the increase in absorbance at the beginning of the fermentation. A significant difference (p > 0.0001) in the inflection time of absorbance down‐curve between the control and PYF wort was also noted.     

Premature yeast flocculation factors from barley malt present in both malt husk and the non‐husk part

In the present study, small‐scale fermentations of seven malts from different maltsters in China were used to monitor their premature yeast flocculation (PYF) potential. Husk exchange was applied between PYF negative malt (PYF‐) and PYF positive malt (PYF+) to investigate the PYF factors potentially present in the husk. The results showed that PYF factors were present in both malt husk and the non‐husk part. The two factors showed various ratios among different PYF+ malts, and either of them could induce PYF if it reached the threshold. Moreover, the major antimicrobial substances damaging the yeast cells were in the non‐husk part. Copyright © 2014 The Institute of Brewing & Distilling     

改善酵母絮凝、稳定啤酒质量

介绍了酵母的絮凝性及其表现,影响酵母絮凝性的因素;重点介绍我们从麦汁组成、Ca2+添加控制、通风供氧量、酵母添加量等方面改善酵母絮凝状态,稳定产品质量。