利用固定化酵母进行黄酒主发酵的初步研究

该文以海藻酸钙凝胶为固定化载体,从酵母浓度、海藻酸钠浓度、氯化钙浓度3方面来探究黄酒主发酵阶段的最佳固定化条件,确定了酵母浓度为109个/mL,海藻酸钠浓度为2.0%,氯化钙浓度为4%。同时将其与传统游离酵母的发酵曲线进行对比,并且在实验室条件下连续进行了12次固定化酵母发酵,结果显示主发酵结束时酒样的酒精度在7.4%vol左右(与游离发酵结果类似),稳定性较为理想。     

固定化酵母在糯米酒中的应用研究

以海藻酸钠为栽体,以CaCl2和ZnSO4为交联剂制作固定化酵母,并将其应用于糯米稠酒的连续发酵。研究结果表明,当海藻酸钠溶液浓度为2．5％,以CaCl2溶液为交联剂制备的固定化酵母,应用于糯米稠酒生产的效果较好。连续发酵5批,所得糯米稠酒米香、醇香浓酸甜适中,酒体醇厚,无苦涩味。     

Production of white wine by Saccharomyces cerevisiae immobilized on grape pomace

White wine was produced with Saccharomyces cerevisiae cells immobilized on grape pomace, by natural adsorption. The support, the main solid waste from the wine industry, consisted of the skins, seeds and stems. Immobilization was tested using different media, namely complex culture medium, raw grape must and diluted grape must. Grape pomace was revealed to be an appropriate support for yeast cell immobilization. Moreover, grape must was shown to be the most suitable medium as immobilized cells became adapted to the conditions in the subsequent alcoholic fermentation in the wine‐making process. The wines produced, either with immobilized cells or with free cells, were subjected to chemical analysis by HPLC (ethanol, glycerol, sugars and organic acids) and by gas chromatography (major and minor volatile compounds); additionally, colour (CIELab) and sensory analysis were performed. The use of immobilized systems to conduct alcoholic fermentation in white wine production proved to be a more rapid and a more efficient process, especially when large amounts of SO₂ were present in the must. Furthermore, the final wines obtained with immobilized cells demonstrated improved sensory properties related to the larger amounts of ethanol and volatile compounds produced. The more intense colour of these wines could be a drawback, which could be hindered by the reutilization of the biocatalyst in successive fermentations. Copyright © 2012 The Institute of Brewing & Distilling     

营养盐在固定化酵母生产蜂蜜酒中影响的研究

对营养盐类物质在固定化酵母生产蜂蜜酒中的影响进行研究,通过L9(34)正交试验确定了复合营养盐添加的最适添加量。     

Alleviation of stuck wine fermentations using salt‐preconditioned yeast

The influence of salt (sodium chloride) on the cell physiology of wine yeast was investigated. Cellular viability and population growth of three wine‐making yeast strains of Saccharomyces cerevisiae, and two non‐Saccharomyces yeast strains associated with wine must microflora (Kluyveromyces thermotolerans and K. marxianus) were evaluated following salt pre‐treatments. Yeast cells growing in glucose defined media exposed to different sodium chloride concentrations (4, 6 and 10% w/v) exhibited enhanced viabilities compared with nontreated cultures in subsequent trial fermentations. Salt ‘preconditioning’ of wine yeast seed cultures was also shown to alleviate stuck and sluggish fermentations at the winery scale, indicating potential benefits for industrial fermentation processes. It is hypothesized that salt induces specific osmostress response genes to enable yeast cells to better tolerate the rigours of fermentation, particularly in high sugar and alcohol concentrations. Copyright © 2014 The Institute of Brewing & Distilling     

利用原生质体融合技术构建梨酒酵母工程菌

以菌株酿酒酵母Saccharomyces cerevisiae YDJ05及产香酵母Issatchenkia orientalis YS03为融合亲本X和Y,通过原生质体融合技术构建适合梨酒酿造的酵母工程菌,研究结果表明:利用EMS诱变亲本菌株Y,得到了一株精氨酸营养缺陷型菌株,亲本菌株X和Y采用蜗牛酶液在35℃下处理100min,得到菌株X、Y的原生质体融合率分别为93.6%、94.2%,再生率分别为27.8%、31.6%。以加热的方式灭活亲本菌株X,灭活时间为14min。在以PEG为促融剂的条件下对两株菌进行原生质体融合,经过优选得到融合子DJ02,其产酒精率、产香率等指标最优,分别达到了9.87%、0.37g/L。      

固定化多菌种发酵海藻酒的研究

采用PVA固定化酿酒酵母和产香酵母发酵海带，酿造海藻酒。对游离细胞与固定化细胞的分批发酵和连续发酵的动力学进行了研究并建立了相应的发酵动力学方程。实验结果表明：酿酒酵母和产香酵母最佳配比为4：1，发酵温度20℃，固定化细胞分批发酵和连续发酵凝胶粒的充填系数分别为0．25和0．5，游离混合细胞的发酵时间为7d，固定化细胞连续发酵稀释速率0．12/h，发酵时间为0．5d左右。经160d连续发酵实验，PVA固定化细胞粒子的机械强度良好。     

Continuous production of pectinase by immobilized yeast cells on spent grains

A yeast strain secreting endopolygalacturonase was used in this work to study the possibility of continuous production of this enzyme. It is a feasible and interesting alternative to fungal batch production essentially due to the specificity of the type of pectinase excreted by Kluyveromyces marxianus CCT 3172, to the lower broth viscosity and to the easier downstream operations. In order to increase the reactors' productivity, a cellulosic carrier obtained from barley spent grains was tested as an immobilization support. Two types of reactors were studied for pectinase production using glucose as a carbon and energy source--a continuous stirred tank reactor (CSTR) and a packed bed reactor (PBR) with recycled flow. The highest value for pectinase volumetric productivity (P(V)=0.98 U ml(-1) h(-1)) was achieved in the PBR for D=0.40 h(-1), a glucose concentration on the inlet of S(in)=20 g l(-1), and a biomass load in the support of X(i)=0.225 g g(-1). The results demonstrate the attractiveness of the packed bed system for pectinase production.     

固定化复合酵母生产黍米黄酒的新工艺

以黍米为原料 ,采用固定化复合酵母细胞技术发酵生产黄酒 ,确定了最佳工艺条件 :固定化复合酵母细胞接种配比为酿酒酵母∶产酯酵母 =3∶2 ;固定化复合酵母载体填充率 8% ;发酵温度2 0℃ ;发酵时间 96h ;起始 pH4 0。在该条件下发酵生产的黄酒 ,口感风味较好 ,在缩短了发酵时间的同时总氨基氮和总酯含量较传统工艺都有了较大的提高。     

Effects of temperature, ammonium and glucose concentrations on yeast growth in a model wine system

In enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae.     

Overexpression of vacuolar H+‐ATPase‐related genes in bottom‐fermenting yeast enhances ethanol tolerance and fermentation rates during high‐gravity fermentation

Vacuolar H⁺‐ATPase (V‐ATPase) is thought to play a role in stress tolerance. In this study it was found that bottom‐fermenting yeast strains, in which the V‐ATPase‐related genes DBF2, VMA41/CYS4/NHS5 and RAV2 were overexpressed, exhibited stronger ethanol tolerance than the parent strain and showed increased fermentation rates in a high‐sugar medium simulating high‐gravity fermentation. Among the strains examined, the DBF2‐overexpressing bottom‐fermenting yeast strain exhibited the highest ethanol tolerance and fermentation rate in YPM20 medium. Using this strain, high‐gravity fermentation was performed by adding sugar to the wort, which led to increased fermentation rates and yeast viability compared with the parent strain. These findings indicate that V‐ATPase is a stress target in high‐gravity fermentation and suggests that enhancing the V‐ATPase activity increases the ethanol tolerance of bottom‐fermenting yeast, thereby improving the fermentation rate and cell viability under high‐gravity conditions. Copyright © 2012 The Institute of Brewing & Distilling     

产酯酵母在黄酒生产中的应用及增香降度研究

探索一种新型黄酒的发酵方法,将产酯酵母与普通黄酒酵母共同发酵,得到一种新型黄酒,其香味较普通黄酒增加、酒精度降低,并对其香气成分进行分析。     

Optimization of alcohol‐free beer production by lager and cachaça yeast strains using response surface methodology

Alcohol‐free beers (AFBs) are an attractive segment of the beer market both for the brewing industry and for consumers. While AFBs produced by arrested/limited fermentation often suffer from a lack of volatile compounds, beer flavour can be improved by yeast selection and optimization of fermentation conditions. The yeast selection strategy was demonstrated by comparing traditional lager yeast with selected cachaça yeast strains. Correspondingly, response surface methodology was used to enhance the formation of the flavour‐active volatile compounds by optimization of the fermentation conditions (original wort extract, fermentation temperature, pitching rate). Statistical analysis of the experimental data revealed the relative significance of process variables and their interactions. The developed quadratic model describing the responses of total esters and higher alcohols to changes in process variables was used to predict the ideal fermentation conditions in terms of flavour formation. The predicted conditions were experimentally verified and alternative strategies of AFB production are suggested. Copyright © 2016 The Institute of Brewing & Distilling     

Effect of a halophilic aromatic yeast together with Aspergillus oryzae in koji making on the volatile compounds and quality of soy sauce moromi

Koji making is an essential step in the production of high‐quality soy sauce. In this study, we inoculated koji with a halophilic aromatic yeast (Zygosaccharomyces rouxii) and Aspergillus oryzae and investigated the effects on the volatile compounds and quality of soy sauce moromi. Our results suggest that the optimal yeast inoculation was approximately 1.5 × 10⁶ yeast per gram of koji, and excessive yeast greatly decreased A. oryzae enzyme activity. In comparison with the control group, there were no significant changes in the concentrations of amino nitrogen, total titratable acids, total soluble nitrogen and reducing sugar by extending the fermentation time during the first fermentation month, whereas the concentration of glutamate in the yeast‐inoculated sample increased by 46.16% and the arginine concentration decreased by 61.07%. After the second fermentation month, 17, 38 and 38 volatile components were identified by GC–MS in C1, C2 and C5, respectively. Moreover, a large number of volatile components, such as 2‐Methoxy‐4‐vinylphenol, ethyl acetate and 1‐Octen‐3‐ol were found in C2 and C5. And the total contents of volatile compounds in C2 were obviously higher than C5. This work furthers our understanding of the traditional multistrain koji making and provides a new method for enhancing the quality and flavour of soy sauce.     

Co‐inoculation of yeast and lactic acid bacteria to improve cherry wines sensory quality

This study examined the effect of co‐inoculation of yeast and lactic acid bacteria (LAB) on the chemical and sensory characteristics of cherry wines, in comparison with a traditional sequential culture. Three LABs were investigated, including two O. oeni (SG26 and Viniflora) and one L. plantarum (PL18). All co‐inoculations significantly shortened the fermentation time (average 8 days earlier) to reach a stable level of residual sugar (<2 g L^?1) and L‐malic acid (<0.5 g L^?1), and no inhibitory effect on the yeast proliferation was observed. For volatiles determined, co‐culture with SG26 produced the greatest amount of volatile components (138.5 mg L^?1), whereas sequential inoculation with PL18 had the lowest level (119.6 mg L^?1). PCA result revealed that different LABs had diverse influences on the volatile profile of cherry wines, and sensory analysis confirmed that these samples presented distinct sensory profiles, and particularly, a stronger note of fruity was perceived when co‐culture was used.     

A novel steamed bread making process using salt‐stressed baker’s yeast

The process of applying salt‐stressed baker’s yeast during southern style Chinese steamed bread dough preparation was examined. Baker’s yeast was stressed in 7% salt solution then mixed into dough, which was then evaluated for dough fermentation producing gas, dough expansion, texture profile analysis (TPA), colour, specific volume, spread ratio and sensory analysis. The results of this study pointed out salt‐stressed baker’s yeast produced significant amount of gas and dough expansion, particularly after 40 min of salt stressing. The texture of steamed bread was softer (463.08 g) than control (541.35 g) (P < 0.05), greater in specific volume (3.15 cm³ g^?1) than control (2.89 cm³ g^?1) (P < 0.05), had a lower spread ratio (1.45) than control (1.74) (P < 0.05) and a significantly improved sensory properties for taste (90.6) than control (81.6) (P < 0.05) were obtained.     

West African sorghum beer fermented with Lactobacillus delbrueckii and Saccharomyces cerevisiae: fermentation by‐products

Physicochemical quality parameters and volatile fermentation by‐products were determined in West African sour sorghum beer (pito) fermented with pure cultures of Lactobacillus delbrueckii and Saccharomyces cerevisiae compared with pito prepared by traditional spontaneous fermentation. Levels of by‐products were also compared with those found in similar beer types. Similar levels of apparent extract, alcohol, pH, lactic acid and bitterness were obtained for pure culture and traditional fermentations, although differences were observed in colour and turbidity. Significant statistical differences were obtained for all of the volatile aroma compounds analysed. The pure culture approach resulted in a higher level of total volatile compounds (353 mg/L) of which higher alcohols accounted for 88%, predominately n‐propanol. The traditional approach had total volatiles of 229 mg/L with 86% higher alcohols but with iso‐amyl alcohol predominating. Ester levels were low in the pure culture beer but with a relatively high level of acetaldehyde. Fermenting pito with pure cultures yielded a product with similar physicochemical quality as traditional pito but with a suggestion of a more pronounced aroma whose impact on the overall product quality will require consumer acceptance and sensory evaluation. © 2019 The Institute of Brewing & Distilling