乙醇含量对广东黄酒香气成分的影响

该文研究了乙醇含量对黄酒挥发性香气成分的影响。采用顶空固相微萃取结合气质联用（HS-SPME-GC/MS）技术对在发酵过程中添加6个乙醇含量（25%vol、30%vol、35%vol、40%vol、45%vol、50%vol）的食用酒精发酵的黄酒进行检测。结果显示,除了发酵时添加50%vol食用酒精的黄酒样品,其他每个乙醇含量的黄酒样品的香气成分都有独特成分,加50%vol食用酒精的黄酒所含主要香气成分相对含量最高,达到了80.28%,而35%vol的相对含量最少,为39.09%;风味成分比例较大的酯类、醇类和工厂黄酒有约50%的相同成分,不同成分推测是受乙醇含量的影响,表明乙醇含量对黄酒挥发性香气成分的形成有较为明显的差别。     

Vacuum-assisted block freeze concentration applied to wine

Vacuum is an assisted technique to improve the efficiency of freeze concentration process, and wine is an interesting raw material to be concentrated. In this study reported the vacuum-assisted block freeze concentration to force the separation of solutes from a frozen wine sample. By applying vacuum (40 kPa), the solids content in the concentrated fraction increased significantly compared to the initial value (8°Brix), reaching a value near of 21°Brix after 5 min, although decreasing over time, indicated that the concentrated extract was collected mostly in the first fractions. The efficiency achieved high values near of 90% in a short time (15 min, 45 ml of initial sample), with high values of ice purity over time of suction. The pH, alcohol, acidity and total polyphenol content increased significantly in the concentrated sample (50% of concentrate) compared the fresh wine. The color evaluation indicating that cryoconcentrate (50% of concentrate) was darker than the initial sample, with a ΔE* value > 40 CIELAB units. The vacuum-assisted block freeze concentration applied to wine is an effective technique to obtain a concentrated sample with attractive properties for possible gastronomic use.Industrial relevanceThe vacuum assisted block freeze concentration allows producing wine concentrates with attractive properties, such as a high solid content, darker color and higher alcohol content than the initial sample. In this work has applied vacuum (40 kPa) as an assisted technique to improve the efficiency of block freeze concentration applied to wine, obtaining promissory results.     

乙醇传感器法测定葡萄酒和黄酒中乙醇的含量

建立了生物传感器法测定葡萄酒和黄酒中乙醇含量的分析方法。结果表明:乙醇含量在2~80μL/100mL浓度范围内线性关系良好,相关系数为0.9997;加标回收率(n=3)在99.22%~101.59%之间;精密度和重复性(n=4)的RSD%低于1%。与国标酒精计法测定结果对比,两种方法无显著差异。该法具有无需样品前处理、特异性好、灵敏度高、测定速度快等优点,适用于企业对发酵过程控制和产品的质量检测。      

葡萄酒中乙醇含量的气相色谱法测定

为建立气相色谱法直接测定葡萄酒中的乙醇含量的方法,将样品稀释后直接进样,经过DB-FFAP毛细管色谱柱分离后用气相色谱FID检测器进行分析。在所建立的最佳实验条件下,葡萄酒中乙醇峰得到有效分离,线性良好,最低检出限为0.01%,相对标准偏差为3.6%~4.0%,平均回收率为90%~95%。说明该方法灵敏、简单易操作、准确可靠,用此法检测葡萄酒中的乙醇含量,结果满意。     

Fermentative aptitude of non-Saccharomyces wine yeast for reduction in the ethanol content in wine

Over the last few decades, there has been a progressive increase in the ethanol content in wines due to global climate change and to the new wine styles that are associated with increased grape maturity. This increased ethanol content can have negative consequences on the sensory properties of the wines, human health, and economic aspects. Several microbiological approaches for decreasing the ethanol content have been suggested, such as strategies based on genetically modified yeasts, the adaptive evolution of yeasts, and the use of non-Saccharomyces yeast. In the present study, we investigated the interspecies and intraspecies variability of some non-Saccharomyces wine yeast species under anaerobic fermentation conditions. Across different grape juices and fermentation trials, Hanseniaspora uvarum, Zygosaccharomyces sapae, Zygosaccharomyces bailii, and Zygosaccharomyces bisporus promoted significant reductions in ethanol yield and fermentation efficiency in comparison with Saccharomyces cerevisiae. The diversion of alcoholic fermentation and the abundant formation of secondary compounds might explain the marked reduction in ethanol yield, as determined through the segregation of the majority of the strains according to their species attributes observed using principal component analysis. These data suggest that careful evaluation of interspecies and intraspecies biodiversity can be carried out to select yeast that produces low-ethanol yields.     

Microbiological and biochemical studies on traditional Indian palm wine fermentation

Microorganisms that are responsible in fermenting wild date palm (Phoenix sylvestris) sap into wine (toddy) were isolated and identified. Saccharomyces cerevisiae, Schizosaccharomyces pombe, Acetobacter aceti, Acetobacter rancens, Acetobacter suboxydans, Leuconostoc dextranicum, Micrococcus sp., Pediococcus sp., Bacillus sp. and Sarcina sp. were encountered in the freshly tapped sap. A majority of these microorganisms were also isolated from the traditionally fermented fresh toddy samples. In a comparitive study on the fermentation of fresh sap and fresh toddy, certain variations in the growth pattern of these microorganisms were noticed. In addition to this, the amount of ethanol, volatile acid, non-volatile acid and esters produced during these fermentations also varied.Data regarding the microbiological and biochemical changes that occur during fermentation of fresh sap and inoculated (field and laboratory) saps are presented.     

葡萄酒、果酒酒精含量测定中计算方法的探讨

葡萄酒、果酒国际GB/T15038-94中规定:测定酒精含量的方法有气相色谱法、密度瓶法和酒精计法,其中气相色谱法测定速度最快、结果最准确,但一般葡萄     

酶电极法测定玫瑰酒中的乙醇含量

乙醇氧化酶经固定化制成酶膜与过氧化氢电极构成酶电极,研究了乙醇酶电极分析方法的分析条件及参数,与常规比重瓶法测定乙醇含量进行比较,结果显示两者之间有较好的一致性.采用酶电极法测定玫瑰酒中乙醇含量具有成本低、方法简便、快速等优点.     

Effects of ethanol,tannin and fructose on the headspace concentration and potential sensory significance of odorants in a model wine

The effects of ethanol (8, 10, 12, 14, and 16% v/v), tannin (500, 1000, and 1500 mg/L) and fructose (200 and 2000 mg/L) concentrations on the headspace of eight selected odorants were investigated using headspace solid phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS). Analysis of variance results (ANOVA) showed significant interaction effects for the majority of odorants (P < 0.05). In general, higher tannin concentration enhanced the release of odorants while fructose induced a retention effect, both of which were largely dependent upon ethanol concentration. The net magnitude effect was a substantial reduction in the headspace concentration of odorants with the dominant contribution from ethanol concentration. The percent reduction in extracted odorant was more pronounced on larger molecular weight compounds. Further multivariate analysis discriminated model wines with different ethanol concentrations and, to a lesser extent, separated model wines with different fructose and tannin concentrations. Subsequent gas chromatography–olfactometry (GC–O) analysis revealed differences in the estimated odor thresholds of odorants in the model wines. Threshold values increased between 2 and 10,000-fold for 2-methoxyphenol and eugenol, respectively, at higher ethanol, tannin and fructose concentrations. Consequently, odor unit values (OUV) of odorants decreased indicating a reduction in the potential contribution of the odorants to the aroma of model wine. These results highlighted the significant impact that wine matrix interactions can have on wine aroma quality.     

药桑葡萄果酒对高脂血症大鼠的降血脂作用

以Wistar大鼠为研究对象,探讨药桑葡萄果酒对高脂血症大鼠血脂的调节作用。收集动物试验各组动物血清、肝脏、心脏及脂肪组织,测定血清总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白胆固醇（LDL-C）、高密度脂蛋白胆固醇（HDL-C）及相应的抗氧化指标,并对大鼠肝脏和心脏进行组织病理学检查。结果表明,经药桑葡萄果酒灌胃后,与模型组相比,药桑葡萄果酒高、中、低组的TC分别下降了27.87%、36.96%和22.80%（P＜0.05）,TG分别下降了49.38%、62.63%和43.51%（P＜0.05）。药桑葡萄果酒不同剂量组能显著提高大鼠血清超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的活性（P＜0.05）,显著降低血清丙二醛（MDA）的含量（P＜0.05）。适量的药桑葡萄果酒可抑制大鼠肝脏中脂质的积累,改善脂肪肝病变和脂质代谢紊乱,从而降低高脂饮食大鼠体内血脂水平。     

Interaction of pH, ethanol concentration and wine matrix on induction of malolactic fermentation with commercial 'direct inoculation' starter cultures

The effect of the interaction between pH (2.9–3.5), alcohol concentration (12.5–14.5% v/v) and wine matrix (Chardonnay, Grenache blend and Cabernet Sauvignon) on malolactic fermentation (MLF) induced by two commercially available directly inoculated Oenococcus oeni starter cultures was determined. Wine matrix had greatest impact on the rate of MLF, followed by pH and alcohol; the matrix effect was significantly modified by pH and bacterial culture. The rate of L-malic acid degradation by starter culture A was 3.3–61.3% in the Grenache blend and 3.3–4.5% in the Chardonnay wine compared to the Cabernet Sauvignon wine, for the pH/alcohol ranges 2.9/14.5 to 3.5/12.5. L-malic acid degradation rate by starter culture B was lower but less affected by wine matrix. The rate of L-malic acid degradation was closely related to culture viability, with a high rate of L-malic acid degradation being associated with bacterial growth and vice versa . Treatment of two wines in which MLF had previously failed to complete with various combinations of nutrients, carbon fining and heating, restored MLF, suggesting that a growth-limiting nutrient was absent and/or a toxic substance not related to pH, alcohol or SO₂ concentration was present. This work demonstrated that the wine matrix may affect culture viability more significantly than either pH or alcohol concentration. A high rate of MLF was shown to depend on factors permitting bacterial growth, however, the two strains studied responded differently to the wine matrix, suggesting that malolactic bacteria vary in tolerance to various stresses in the wine environment.     

Effects of fining agents on trans-resveratrol concentration in wine

Resveratrol has been identified as a wine component related to moderate wine consumption and a reduction in serum cholesterol levels. Processes such as wine fining that result in loss of resveratrol during winemaking are therefore of interest, and led to these present studies. A number of agents were compared and were found to lower resveratrol levels in all wines to some extent. Results from two studies (1996 and 1997) are reported. The standard addition method was used in combination with High Pressure Liquid Chromatography to calculate resveratrol levels. In Study 1 (1996), recommended maximum levels of all fining agents (Level 3), bentonite, egg white, gelatin + kieselsol and polyvinylpolypyrrolidone (PVPP), lowered resveratrol levels significantly compared to controls (Level 0). Nevertheless, addition of fining agents at Level 0 resulted in resveratrol levels that were significantly higher than those at Level 3, but resveratrol levels in wine from Level 0 were not significantly different from Level 1. In Study 2 (1997), carbon + egg white, and gelatin + kieselsol fining was studied, and their effects differed according to grape variety. Least removal of resveratrol by carbon fining occurred in wine from Cabernet Sauvignon (Vitis vinifera) whereas most removal occurred in wines from Cynthiana (Vitis aestivalis) and Noble (Vitis rotundifolia). Resveratrol levels of control wine were significantly higher than resveratrol levels of wine treated with recommended maximum addition of fining agent in all varieties. Taken overall, any addition of any fining agent lowered resveratrol levels in all wines to some extent, but complex interactions between fining agent and wine variety resulted in different regression trends. While recognising the constraints set by our particular data that could reflect unique circumstances, we are nevertheless able to infer from these trends that low levels of fining agents can be used without statistically significant loss of resveratrol.     

Impact of ethanol on the perception of wine odorant mixtures

Several studies have focused on perceptual interactions in binary odor mixtures, but few on more complex mixtures. The aroma of wine is an example of a complex odor mixture. Our aim was to assess the impact of ethanol on the perception of mixtures of Woody (whiskey lactone) and Fruity (isoamyl acetate) odorants commonly found, physico-chemically and perceptually, in wine. Physico-chemically, reduced whiskey lactone volatility was observed in hydro-alcoholic solutions. Perceptually, a synergy effect by the Woody on the Fruity odor was observed in aqueous solutions, which disappeared with the addition of ethanol. Conversely, the Woody odor was masked in both aqueous and dilute alcohol solutions. In addition, mixed Woody and Fruity odors were found to mask the so-called Alcohol odor. These results underline the importance of perceptual interactions in the perception of wine bouquet.     

Improved fermentation kinetics by wine yeast strains evolved under ethanol stress

Adaptive laboratory evolution works on the principle that populations of cells adapt to their environment over time by natural selection. In this work, we assess adaptive laboratory evolution as a tool to improve the performance of winemaking yeast strains, in order to cope with the challenges of global climate change. Specifically we addressed ethanol tolerance as a way to ensure good fermentation kinetics despite increasing sugar content in musts.     

红葡萄酒澄清工艺中白藜芦醇的变化

采用RP-HPLC方法,测定红葡萄酒澄清处理前后白藜芦醇四种异构体的含量变化,发现:1)澄清处理后红葡萄酒中白藜芦醇总量减少了15.7%;2)下胶和硅藻土过滤主要引起水溶性较强白藜芦醇糖苷含量的减少,损失率达到25.9%;3)速冷处理对红葡萄酒中白藜芦醇的保留率达到100%.     

Microbiological criteria for Listeria monocytogenes in foods under special consideration of risk assessment approaches

This paper shortly summarizes data related to risk assessment of Listeria monocytogenes. From available data on risk assessment, it is concluded that the levels of L. monocytogenes consumed is an important factor affecting the incidence of listeriosis. Foods that do not support the growth of L. monocytogenes are unlikely to be a source of listeriosis, whereas foods that support the growth to high levels, should be the target of risk management efforts. Based on current epidemiological information from several countries, a concentration of L. monocytogenes not exceeding 100/g of food at the time of consumption is of low risk to the consumers. In order not to exceed these levels at the point of consumption, lower levels may need to be applied at the port of entry, for those foods in which growth can occur within the shelf life. In order to establish such levels, knowledge of the shelf life and behaviour of L. monocytogenes in the food during prevailing storage and distribution conditions is needed.     

190612-3气相色谱顶空内标法快速测定料酒中乙醇含量

建立了用气相色谱顶空内标法测定料酒中乙醇含量的方法。试验采用FID检测器,顶空法进样,内标法检测过程快速、简便、准确。本方法乙醇检出限为0.01%vol(S/N=3),标准曲线的线性范围2%～20%vol(r=0.99994)。该方法测定料酒中的乙醇含量,样品加标浓度为2%vol、5%vol、10%vol,加标回收率为99.6%～100.1%,相对标准偏差RSD(n=10)1.07%,方法检测限为0.05%vol。     

A bacterial gene homologous to ABC transporters protect Oenococcus oeni from ethanol and other stress factors in wine

The wine lactic acid bacteria Oenococcus oeni has to cope with harsh environmental conditions including an acidic pH, a high alcoholic content, non-optimal growth temperatures, and growth inhibitory compounds such as fatty acids, phenolic acids and tannins. We here describe characterisation and cloning of the O. oeni omrA gene encoding a protein belonging to the ATP-binding cassette superfamily of transporters. The OmrA protein displays the highest sequence similarity with the subfamily of ATP-dependent multidrug resistance (MDR) proteins, most notably the bacterial Lactococcus lactis LmrA homologue of the human MDR1 P-glycoprotein. The omrA gene proved to be a stress-responsive gene since its expression was increased at high temperature or under osmotic shock. The OmrA protein function was tested in Escherichia coli, and consistent with the omrA gene expression pattern, OmrA conferred protection to bacteria grown on a high salt medium. OmrA also triggered bacterial resistance to sodium laurate, wine and ethanol toxicity. The homologous LmrA protein featured the same stress-protective pattern than OmrA when expressed in E. coli, and the contribution to resistance of both OmrA and LmrA transporters was decreased by verapamil, a well-known inhibitor of the human MDR1 protein. Genes homologous to omrA were detected in other wine lactic acid bacteria, suggesting that this type of genes might constitute a well-conserved stress-protective molecular device.     

Tailoring wine yeast for the new millennium: novel approaches to the ancient art of winemaking

Yeasts are predominant in the ancient and complex process of winemaking. In spontaneous fermentations, there is a progressive growth pattern of indigenous yeasts, with the final stages invariably being dominated by the alcohol-tolerant strains of Saccharomyces cerevisiae. This species is universally known as the 'wine yeast' and is widely preferred for initiating wine fermentations. The primary role of wine yeast is to catalyze the rapid, complete and efficient conversion of grape sugars to ethanol, carbon dioxide and other minor, but important, metabolites without the development of off-flavours. However, due to the demanding nature of modern winemaking practices and sophisticated wine markets, there is an ever-growing quest for specialized wine yeast strains possessing a wide range of optimized, improved or novel oenological properties. This review highlights the wealth of untapped indigenous yeasts with oenological potential, the complexity of wine yeasts' genetic features and the genetic techniques often used in strain development. The current status of genetically improved wine yeasts and potential targets for further strain development are outlined. In light of the limited knowledge of industrial wine yeasts' complex genomes and the daunting challenges to comply with strict statutory regulations and consumer demands regarding the future use of genetically modified strains, this review cautions against unrealistic expectations over the short term. However, the staggering potential advantages of improved wine yeasts to both the winemaker and consumer in the third millennium are pointed out.