Inhibition of spoilage lactic acid bacteria by lysozyme during wine alcoholic fermentation

The efficacy of lysozyme against indigenous lactic acid bacteria (LAB) and four inoculated spoilage LAB cultures was investigated in laboratory scale Chardonnay winemaking trials (at pH 3.8). These LAB cultures included Lactobacillus kunkeei, Lactobacillus brevis, Pediococcus parvulus , and Pediococcus damnosus . Three concentrations of lysozyme were used: 0, 125 and 250 mg/L. Alcoholic fermentation of the grape juice was carried out at 20±0.5°C using Saccharomyces cerevisiae . Lysozyme did not have any negative impact on yeast growth and sugar reduction. This enzyme was found to be very effective in inhibiting the growth of all four LAB cultures investigated. Under the given experimental conditions, as high as an 8 log cell reduction was obtained for some of the strains. The acetic acid production by L. brevis and L. kunkeei was significantly reduced in the treatments with 125 and 250 mg/L lysozyme added ( P < 0.01). The effect of lysozyme on the cells of the LAB cultures was examined under a scanning electron microscope. It is evident that lysozyme had a detrimental impact on the cells of these cultures. Based on these observations, it is concluded that lysozyme may be a useful tool for winemakers to control the growth of spoilage LAB and to reduce the production of volatile acids. The addition of lysozyme may also prevent the increase of volatile acidity during stuck/sluggish alcoholic fermentation. This tool is particularly useful in high pH wines where SO₂ is less effective.     

Biomarkers for detecting nitrogen deficiency during alcoholic fermentation in different commercial wine yeast strains

Nitrogen deficiencies in grape musts are one of the main causes of stuck or sluggish wine fermentations. Several putative biomarkers were tested in order to analyze their appropriateness to detect nitrogen stress in the yeast. To this aim, four commercial wine strains (PDM, ARM, RVA and TTA) were grown in a synthetic grape must with different nitrogen concentrations. Trehalose accumulation, arginase activity and the expression of eleven genes were tested in these wine strains, known to have different nitrogen requirements. The overall response of the four strains was similar, with differences in response intensity (PDM and RVA with higher intensity) and response time (which was also related with nitrogen consumption time). Trehalose response was mostly related to entry into the stationary phase, whereas arginase activity was responsive to nitrogen depletion, although its measurement is too complicated to be used for routine monitoring during winemaking. The expression of the genes DAL4, DAL5, DUR3 and GAP1 was clearly related to nitrogen depletion and thus, GAP1 and DAL4 were selected as markers of nitrogen deficiency. In order to adapt expression analysis to winemaking conditions, the original strains were transformed into reporter strains based on the expression of green fluorescent protein (GFP) under control of the promoters for GAP1 and DAL4. The transformants had a similar fermentative capacity to the parental strains and were able to detect alterations in yeast physiological status due to nitrogen limitations.     

Influence of different commercial active dry yeasts on histaminol production during wine alcoholic fermentation

The performance of different selected yeast strains regarding the capacity to convert histidine into histaminol during fermentation has been described and discussed in a model grape must (Chardonnay). First, the activity of 10 commercial active dry yeast strains (ADY) in the native grape must both with and without a nitrogen supplementation has been compared. In the second set of fermentations, after selecting the four best‐performing strains, their performances using four different nitrogen sources have been tested. During fermentation process it was not possible to identify a common trend. In some cases, histaminol content appeared related to the nutrient supplementation, however, in other cases a different behaviour emerged. However, as shown by the experimental evidences, among the two variables considered the nature of yeast strain was slightly prevalent.     

Effect of ammonium concentration on alcoholic fermentation kinetics by wine yeasts for high sugar content

Kinetics of alcoholic fermentation by Saccharomyces cerevisiae wine strains in a synthetic medium with high sugar content were established for different nitrogen initial content and are presented for four strains. The composition of the medium was close to grape must except that the nitrogen source consisted mainly in ammonium and was varied from 120 to 290 mg N/l assimilable nitrogen. The overall nitrogen consumed was also estimated in order to determine nitrogen requirement variability. The effect of assimilable nitrogen was in general greater on sugar consumption rates than on growth and three kinds of effect on sugar consumption rates were observed: (i) existence of an optimal initial nitrogen level for a maximal sugar consumption rate (inhibition if excess), (ii) no effect of nitrogen beyond the intermediary level (saturation), (iii) sugar consumption rate proportional to the initial nitrogen level (activation). In all cases, the amount of consumed nitrogen increased with its initial concentration and so did the fructophilic capacity of the strains. The optimal requirement varied from 0.62 to 0.91 mg N/g of sugars according to different strains. There was no general correlation between the sugar assimilation rates and the nitrogen requirement.     

Using headspace solid phase micro-extraction for analysis of aromatic compounds during alcoholic fermentation of red wine

Timely monitoring of changes in the type and quantity of aromatic compounds throughout the must fermentation process provides useful information for wine makers. This paper aimed to use headspace solid phase micro-extraction coupled with gas chromatography (HS-SPME/GC–MS) to analyse aromatic compounds produced during must alcoholic fermentation. The results showed that both qualitatively and quantitatively, the PDMS/CAR/DVB fibre was suitable for extracting aromatic compounds in wine. The amount of alcohols, esters, acids and monoterpenes absorbed on the SPME fibre were influenced by the ethanol content. Calibration curves with a high correlation (R² > 0.900) obtained in seven ethanol contents (2%, 4%, 6%, 8%, 10%, 12% and 14%) were established to quantitatively determine the amount of aromatic compounds during alcoholic fermentation. A validated HS-SPME method for determining aromatic compounds was used to monitor aromatic compounds during Syrah alcoholic fermentation. This modified HS-SPME method was proved to be useful for controlling the oenological process.     

木棉花全汁发酵酒生产工艺的研究

以木棉花为原料,采用全汁发酵技术,开发出新型木棉花发酵酒。在单因素试验的基础上,对木棉花酒的发酵温度、发酵时间、含糖量和酿酒酵母的接种量进行了优化,通过4因素4水平的正交试验,确定发酵条件的最佳组合。通过试验得到的最佳发酵工艺参数为发酵最佳时间5d,发酵温度25℃,酵母接种量0.2%,糖的含量15%;4因素的显著影响程度为含糖量发酵温度发酵时间酵母接种量。最终得到的成品的感官指标、理化指标及卫生指标均满足国标。     

如何建造葡萄酒水泥发酵罐

酿造和储存葡萄酒如何才能做到用最低的成本达到最理想化的状态?在欧洲和南美洲,葡萄酒酿造和储存过程中主要使用两种类型的罐:不锈钢罐和水泥罐。目前普遍采用的不锈钢罐非常适合储存葡萄酒,但是有两个缺陷:※钢材价格昂贵;※钢材的隔温性能不好,罐中储存的葡萄酒很容易随着外     

葡萄酒酿造中苹果酸-乳酸发酵的应用

苹果酸-乳酸发酵(MLF)是葡萄酒酿造中非常重要的二次发酵过程,可有效降低葡萄酒中的苹果酸,突出果香,改善口感,是葡萄酒生物降酸的主要方法.本文介绍了苹果酸-乳酸发酵在葡萄酒酿造中的作用,以及苹果酸一乳酸发酵的诱导和抑制,对影响苹果酸-乳酸发酵的环境因素和现代发酵工程技术在苹果酸-乳酸发酵中新的应用与发展也作了阐述.     

低度山楂起泡酒的研制

以山楂为原料,添加法国进口葡萄酒干酵母进行发酵,制得了低酒度、自然红色的含汽山楂酒。该产品口感良好,澄清透明、性质稳定,其酒精度5%(V/V)、总糖(g/L)≥50、总酸(g/100mL)0.8~1.0、20℃时瓶内二氧化碳压力≥0.3MPa,符合国家起泡酒标准。     

低度浸制梅酒的研制

本文介绍了低度浸制梅酒的生产工艺 ,并对内置梅的制作和果酒澄清方法进行了分析 ,希望能为同仁提供一些可行的方法     

混菌发酵生产酒饮料

论述了混菌发酵生产酒饮料的原理、方法及操作步骤,分析了混菌发酵生产酒饮料的发展前景及推广价值。      

早酥梨酒酿造中葡萄酒酵母的选择研究

以甘肃的早酥梨为原料进行发酵研究,通过考察不同酿酒酵母对早酥梨酒发酵中可溶性固形物含量(SSC)、残糖含量、酒精度、果酒品质和感官评价等理化指标的影响,最终证明酿造早酥梨酒最适宜的菌种为葡萄酒酵母。     

Effect of alternative techniques to ageing on lees and use of non-toasted oak chips in alcoholic fermentation on the aromatic composition of red wine

The aim of this work was to evaluate the effect of different enological treatments on the volatile composition of red wine: ageing on lees with and without adding β-glucanase enzymes; the use of a commercial yeast derivative with and without β-glucanase enzymes; and the use of non-toasted chips in fermentation. The results indicated that the presence of chips during the fermentation enhanced the formation of 2-phenylethanol, ethyl esters and fusel alcohol acetates, but affected the levels of some of the lactones and volatile phenols studied negatively. In addition, it was found that wine lees and commercial yeast derivatives can bind some of the volatile compounds studied, mainly ethyl esters and fusel alcohol acetates. After 6 months in bottle, in general, the differences found between the control wine and wines fermented with chips were maintained. However, between the control wine and the wines treated with natural or commercial yeast, the differences disappeared, although not for all the compounds studied. Finally, an important effect of the addition of β-glucanase enzymes was not observed.     

纤维素酒精发酵的研究进展

本文介绍了纤维素的结构、特征和纤维素酒精发酵的途径,并综述了目前国内外纤维素酒精发酵的研究进展,特别是基因工程、固定化等现代生物工程技术在这一领域的应用。     

糖分对葡萄酒发酵的影响

糖是葡萄酒发酵中酵母菌生长代谢所必须的能源,其种类和含量对酵母菌的发酵能力和代谢产物的生成影响很大。该文从糖种类、糖含量、加糖方式等方面对葡萄酒发酵的影响进行了综述及分析,以期为葡萄酒酿造中糖的选择和品质控制提供理论依据。     

枳椇子对葡萄酒发酵的影响

以葡萄和枳椇子为原料进行果酒混合发酵,通过3因素3水平对酒精发酵阶段进行正交试验.试验表明,当枳椇子与葡萄配比为1:4,加糖量为15％,接种量为1‰,在该条件下酒精产量最高为14.56％vol.利用枳椇子混合发酵进行在葡萄果酒放大发酵试验,对产物进行薄层分析,枳椇子发酵的葡萄酒比单一葡萄发酵成分中多含有二糖和果糖.     

利用WL营养培养基鉴定葡萄酒中的相关酵母菌

采用WL营养培养基对自然发酵前、中、后期出现的酵母菌进行了初步的分类鉴定。产膜的假丝酵母、葡萄汁有孢汉逊酵母及酿酒酵母在自然发酵初期占据主导地位,主要来自葡萄浆果表面;发酵中期主要为毕赤氏酵母;后期则全部为酵母属的酿酒酵母。WL营养培养基对于监测葡萄酒发酵过程中酵母菌群的变化十分有力,可以作为葡萄酒相关酵母鉴定的辅助手段。     

木聚糖酶在玉米原料酒精发酵中的应用研究

探讨了木聚糖酶对玉米原料酒精发酵的影响.经优化后木聚糖酶的最适使用工艺为:木聚糖酶在发酵开始时加入,添加量为170U/g,料水比为1:2.5,初始pH值为自然.与对照组相比,原料出酒率提高5.93%,发酵周期缩短了12h,表明木聚糖酶对玉米原料酒精发酵有明显的促进作用.