外源添加单一氨基酸对桑葚酒风味品质的影响

为探究外源添加氨基酸在改善桑葚酒风味品质中的影响,在桑葚果汁中分别添加400 mg/L的异亮氨酸（Ile）、亮氨酸（Leu）、苯丙氨酸（Phe）和缬氨酸（Val）制备桑葚酒,并分析桑葚酒理化指标、挥发性风味物质和感官品质。结果表明,与对照相比,外源添加单一氨基酸可显著增加桑葚酒的挥发性风味物质含量（42.38～84.58 mg/L）（P＜0.05）,添加Ile显著增加活性戊醇、乙酸活性戊酯含量,添加Leu显著增加异戊醇、乙酸异戊酯含量,添加Phe显著增加苯乙醇和乙酸苯乙酯的含量,添加Val显著增加异丁醇和乙酸异丁酯含量,添加四种氨基酸都能增加辛酸乙酯的含量（P＞0.05）;添加Phe可提高桑葚酒花香,添加Ile、Leu或Val提高果香,添加四种氨基酸的桑葚酒的口感评分均显著提高（P＜0.05）。     

REDUCTION OF HIGHER ALCOHOLS BY FERMENTATION WITH A LEUCINE-AUXOTROPHIC MUTANT OF WINE YEAST

Several auxotrophic mutants requiring branched chain amino acids (valine, leucine, or isoleucine) were isolated in a strain of Montrachet wine yeast. They were tested for their ability to produce lowered amounts of higher alcohols (‘fusel oil’: isobutyl, active amyl, and isoamyl alcohols) in grape juice fermentations. One strain which required leucine was especially good in this respect. This mutation is recessive and is the result of a deficiency for the enzyme α-isopropylamate dehydratase. In trial fermentations with this mutant, the resulting wines contained up to 20% less total fusel oil and 50% less isoamyl alcohol compared to the parent Montrachet strain. An experienced taste panel did not discern any gross degradation of taste quality in wine made with the mutant strain compared to that made with the parent strain. The mutant strain could be of commercial importance in preparation of distilling material for alcoholic beverages since the reduced fusel oil content would not require any special distillation procedures which are normally used to avoid the unpleasant flavour associated with concentrated higher alcohols. Reduction of the isoamyl alcohol content is particularly significant since this fusel oil component is usually present in the highest amount.     

Biosynthesis of higher alcohol flavour compounds by the yeast Saccharomyces cerevisiae: impact of oxygen availability and responses to glucose pulse in minimal growth medium with leucine as sole nitrogen source

Higher alcohol formation by yeast is of great interest in the field of fermented beverages. Among them, medium‐chain alcohols impact greatly the final flavour profile of alcoholic beverages, even at low concentrations. It is widely accepted that amino acid metabolism in yeasts directly influences higher alcohol formation, especially the catabolism of aromatic and branched‐chain amino acids. However, it is not clear how the availability of oxygen and glucose metabolism influence the final higher alcohol levels in fermented beverages. Here, using an industrial Brazilian cachaça strain of Saccharomyces cerevisiae, we investigated the effect of oxygen limitation and glucose pulse on the accumulation of higher alcohol compounds in batch cultures, with glucose (20 g/l) and leucine (9.8 g/l) as the carbon and nitrogen sources, respectively. Fermentative metabolites and CO₂/O₂ balance were analysed in order to correlate the results with physiological data. Our results show that the accumulation of isoamyl alcohol by yeast is independent of oxygen availability in the medium, depending mainly on leucine, α‐keto‐acids and/or NADH pools. High‐availability leucine experiments showed a novel and unexpected accumulation of isobutanol, active amyl alcohol and 2‐phenylethanol, which could be attributed to de novo biosynthesis of valine, isoleucine and phenylalanine and subsequent outflow of these pathways. In carbon‐exhausted conditions, our results also describe, for the first time, the metabolization of isoamyl alcohol, isobutanol, active amyl alcohol but not of 2‐phenylethanol, by yeast strains in stationary phase, suggesting a role for these higher alcohols as carbon source for cell maintenance and/or redox homeostasis during this physiological phase. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of nitrogen on the biological aging of sherry wine

Nitrogen compounds are essential to the growth and metabolism of yeasts. The uptake and metabolism of nitrogen compounds by Saccharomyces cerevisiae depend not only on the strain and its physiological condition, but also on the chemical and physical properties of its environment. The effect of the addition of different amino acids (L ‐proline, L ‐threonine, L ‐arginine, L ‐glutamic acid, L ‐leucine and L ‐valine) to nitrogen‐depleted natural or nitrogen‐free synthetic wine on the cell growth, flor velum formation and sherry wine compound production was investigated under controlled biological aging by S. cerevisiae var. capensis strain G1 a typical flor yeast. The formation of flor velum was dependent on particular amino acid, oxygen availability and the composition of wine. Consumption of glycerol was related with the cell growth; in contrast, acetaldehyde tended to be released. Amino acid supplementation resulted in the release to wine of amino acids, esters and higher alcohols. The amino acid which was released in nearly all cases was L ‐leucine. Addition of L ‐glutamic acid resulted in the release mainly of ethyl acetate, in the case of L ‐leucine isoamyl alcohols were released, and for L ‐valine isobutanol. In the three cases, 1,1‐diethoxyethane was released in large quantities. The findings might indicate that the regulation of metabolism succeeds in the most efficient balancing of the redox potential. Copyright © 2006 Society of Chemical Industry     

Manipulation of volatile compound transformation in durian wine by nitrogen supplementation

This study evaluated the impact of added diammonium phosphate (DAP) and a L‐leucine‐L‐phenylalanine mixture (Leu+Phe) on durian wine fermentation by Saccharomyces cerevisiae var. bayanus EC‐1118. Changes in yeast cell population, ^oBrix, sugars, organic acids and pH were similar in all fermentations, regardless of nitrogen supplementation at a concentration of 150 mg N L^?1. The supplementation of Leu+Phe accelerated the utilisation and reduced the formation of volatile sulphur compounds such as diethyl disulphide, ethyl thioacetate and 2‐(ethylthio)ethanol, which were 64.3%, 26.0% and 48.4% lower than the control, respectively. Nevertheless, the supplementation of Leu+Phe heightened the production of isoamyl alcohol, 2‐phenylethyl alcohol and their corresponding esters, especially isoamyl acetate was 1.6 times and 2‐phenylethyl acetate was 26.5 times higher than the control. The supplementation with DAP exerted negligible effects on the volatile composition. The results of this study suggest that the addition of specific amino acids may be a novel approach to manipulating durian wine flavour by suppressing or accentuating the formation of certain aroma compounds.     

WORT COMPOSITION AND BEER FLAVOUR. I. THE INFLUENCE OF SOME AMINO ACIDS ON THE FORMATION OF HIGHER ALIPHATIC ALCOHOLS AND ESTERS

Wort, to which was added various amounts of glucose solution containing either (NH₄)₂SO₄ or one of the amino acids alanine, leucine, isoleucine, valine or proline, was fermented, and in the resulting beers the concentrations of ethyl acetate, isoamyl acetate, n-propanol, isobutanol, and amyl alcohols were determined by gas chromatography. The nitrogen source had some effect on the formation of higher alcohols, in addition to the effect due to conversion of some of the amino acids to the corresponding alcohols via the Ehrlich pathway. Ethyl acetate formation was not significantly affected by the nitrogen source, and iso-amyl acetate formation increased when amyl alcohol formation increased.     

荔枝酒酿造过程中氨基酸的变化

利用高效液相色谱法(HPLC)对不同发酵温度的荔枝酒酿造过程中氨基酸含量的动态变化进行了分析研究。结果表明,荔枝汁和荔枝酒中均含有丙氨酸、苏氨酸、缬氨酸、谷氨酸、丝氨酸等14种氨基酸,其中,丙氨酸是荔枝汁和荔枝酒中的主体氨基酸,含量分别达1 139.682 mg/L、341.049～412.161 mg/L。不同发酵温度的荔枝酒酿造动态过程中,其游离氨基酸的种类和含量变化较大,且变化趋势各异。不同贮藏方式对荔枝酒中氨基酸含量和种类影响也不同。通过比较,发酵温度12℃优于15℃,发酵温度为15℃的荔枝酒中氨基酸含量在贮藏过程中变化幅度较大,不稳定,且影响风味的氨基酸较多。     

Production of volatile compounds by Lactobacillus sakei from branched chain α-keto acids

Lactobacillus sakei belongs to the main flora of raw fermented sausages and is used as starter culture. Bacterial starter cultures can convert amino acids to α-keto acids by aminotransferases. These α-keto acids are the precursors of aroma active aldehydes, alcohols and carboxylic acids. In this study the formation of aldehydes, alcohols and carboxylic acids from leucine, isoleucine, valine and the corresponding α-keto acids are analysed in model fermentations with two different strains of L sakei. In the absence and upon addition of leucine, isoleucine and valine they produced 1 μg/ml 3-methylbutanoic, 0.2 μg/ml 2-methylbutanoic acid and 3 μg/ml 2-methylpropanoic acid, respectively. Upon addition of α-ketoisocaproic acid, α-keto-3-methyl-pentanoic acid or α-ketoisovaleric acid the amount of the corresponding carboxylic acid was increased to 40 μg/ml 3-methylbutanoic acid, 20 μg/ml 2-methylbutanoic acid and 35 μg/ml 2-methylpropanoic acid. The response patterns of the strains and amounts of carboxylic acids produced were similar. This behaviour was typical when compared with other strains of L. sakei and suggests general lack of transaminase activity and a limit in the transport of branched chain amino acids and their conversion to volatiles, some of which can contribute to the aroma of fermented sausages.     

氨基酸添加对荔枝酒发酵动力及品质影响

分别添加质量浓度范围为60～480 mg/L的D-丙氨酸、L-精氨酸、L-谷氨酰胺于荔枝汁中,测定其对荔枝酒的发酵动力及发酵过程中产生的非挥发性成分以及挥发性成分的影响。结果显示：添加不同种类与浓度的氨基酸可以不同程度加快可溶性固形物的消耗速率,缩短酵母发酵时间,且总醇类含量增加,酸类和酯类均有明显变化。乙醇含量由空白样的10.52%vol升高到处理样的10.71%vol～11.68%vol,而甘油的含量由6.33 g/L下降至4.17～6.04 g/L,乙醛的含量也明显降低。不同种类与浓度的氨基酸对荔枝酒的影响不同。     

花蜜酒发酵工艺优化及成分分析

为获得花蜜酒最佳酿造工艺,促进其产业化,本文通过单因素实验考察百花蜜酒初始糖度、酵母种类、酵母添加量和发酵温度等因素对花蜜酒感官评价的影响,确定最佳因素组合,并对优化后的花蜜酒进行营养成分、挥发性成分含量和氨基酸含量测定分析。结果表明:花蜜酒的最优发酵工艺参数为百花蜜初始糖度22 °Brix,酵母种类为高活性葡萄酒干酵母,酵母添加量为0.4 g/L,发酵温度15 ℃,发酵时间14 d。在最优发酵工艺条件下检测各指标分别为: 葡萄糖20.0 g/L、果糖76.6 g/L、蔗糖0 g/L、残糖含量15 °Brix、酒精度12.0% vol、苹果酸0.700 g/L、草酸0.049 g/L、16种氨基酸总量32 mg/100 mL,分别是苯丙氨酸、丙氨酸、蛋氨酸、脯氨酸、甘氨酸、谷氨酸、精氨酸、赖氨酸、酪氨酸、亮氨酸、丝氨酸、苏氨酸、天冬氨酸、颉氨酸、异亮氨酸和组氨酸,其中异亮氨酸、天冬酰胺、苯丙氨酸和谷氨酸的含量较高,赋予了花蜜酒丰富的风味。16种挥发性化合物,分别是乙醇、乙酸乙酯、异丁醇、异戊醇、2-甲基丁醇、苯乙醇、1,2,4,5-四甲苯、萘、2,5-二甲基苯甲醛、乙酸苯乙酯、葵酸乙酯、2,4-二叔丁基苯酚、月桂酸乙酯、十四酸乙酯、9-十六碳烯酸乙酯、棕榈酸乙酯,其中,乙醇和苯乙醇的浓度最高,分别为50.13%和38.41%,是花蜜酒风味的主要来源。     

榆耳高F值低聚肽的制备及氨基酸组成分析

以榆耳为原料,提取榆耳中蛋白质,NH4Cl盐析,胰凝乳蛋白酶水解,羧肽酶去除芳香族氨基酸,收集10.6ku～2.0ku超滤膜截留范围的低聚肽,测其氨基酸组成及F值.结果表明,榆耳低聚肽的F值为22.67,支链氨基酸组成为是缬氨酸、亮氨酸和异亮氨酸,含量为34.8％.     

Enantiomer Separation of D-L Branched Amino Acids by Capillary Electrophoresis in Sport Nutritional Supplements

A capillary electrophoresis method was developed for the chiral separation of D‐L valine, isoleucine, and leucine. The separation of derivatized amino acids with 9‐fluorenylmethyl‐chloroformate was performed by micellar electrokinetic capillary chromatography. We optimized the method by varying β‐cyclodextrin and sodium dodecyl sulphate concentrations in the presence of 2‐propanol. The proposed method was applied to the determination of D‐forms of valine, Isoleucine, and leucine in the presence of an excess of relative L forms, in commercial supplements for sport nutrition. Results demonstrated that the separation of enantiomers was possible up to an enantiomeric ratio of 1:100. The analysis of selected products confirmed the enantiomeric purity of utilized amino acids.     

Plasma concentrations and dietary requirements of leucine, isoleucine and valine: studies with the young chick

The minimal requirements of the chick for leucine, isoleucine and valine have been assessed using diets based on wheat, groundnut meal and crystalline amino acids. The results of these studies clearly indicate that a relatively low isoleucine concentration of 0.52% allows satisfactory growth rate and efficiency of food conversion with the dietary levels of leucine and valine maintained at 0.98 and 0.63%, respectively. No beneficial response occurs to further supplementation with isoleucine. However, a higher isoleucine level (0.76 %) augments the requirements of leucine and valine to 1.10 and 0.75%, respectively, as judged by growth and efficiency of food conversion responses. These patterns of interactions are reflected in the plasma concentrations of leucine, isoleucine and valine.     

INFLUENCE OF THE CONCENTRATION OF BRANCHED CHAIN AMINO ACIDS ON THE FORMATION OF FUSEL ALCOHOLS

The influence of concentrations of branched-chain amino acids on the total, anabolic and catabolic production of isobutyl, active amyl, and isoamyl alcohol by Saccharomyces cerevisiae X 2180-1A has been examined in media with high nitrogen levels. It has been found that the total and catabolic production of higher alcohols increased with increasing concentrations of the corresponding amino acids. The anabolic pathway can be suppressed by high levels of the corresponding amino acid. Lower concentrations up to 1 mm for isoleucine and 10mm for leucine stimulate the anabolic formation of active amyl alcohol and isoamyl alcohol respectively. From the data obtained, it is shown that, under the conditions used, 50% or more of the fusel alcohols may arise in a beer wort fermentation from carbohydrates.     

The influence of environmental parameters on the catabolism of branched-chain amino acids by Staphylococcus xylosus and Staphylococcus carnosus

Degradation of the amino acids leucine, isoleucine and valine into branched flavour compounds by Staphylococcus xylosus and Staphylococcus carnosus was studied using resting cell cultures added to a defined reaction medium under different environmental conditions relevant to sausage fermentation. The environmental conditions studied were temperature (12–28°C), NaCl concentration (4.0–12.0% (w/w)) acidity (pH 4.8–5.8) and addition of manganese (0–2.5 mg Mn/kg). Flavour compounds were sampled by automatic static headspace collection and separated/quantified using gas chromatography/flame ionization detection (GC/FID). Main volatile catabolic products of leucine, isoleucine and valine were 3-methylbutanoic, 2-methylbutanoic and 2-methylpropanoic acids, respectively. The generation of branched flavour compounds was influenced significantly by most of the investigated environmental parameters, but in particularly by temperature and NaCl.Raising the temperature increased the production of branched-chain acids by both S. xylosus and S. carnosus, whereas increasing NaCl concentration had a clear negative effect, reducing the concentrations of branched-chain acids for both species but in particularly for S. carnosus. The acidity of the medium was also important for both Staphylococcus spp., but with opposite effects. Lowering pH decreased the generation of branched-chain acids by S. carnosus but increased the generation by S. xylosus. In addition, several two-factor interactions between temperature, NaCl concentration and pH were significant. Manganese addition increased the branched-chain acid concentration slightly for S. xylosus but not for S. carnosus.     

Development of normal and branched chain volatile fatty acids during the fermentation process in the manufacture of fish sauce

The formation of volatile fatty acids (VFAs) in fish sauce was investigated. When fish were allowed to spoil prior to salting, very high concentrations of VFAs were produced. The increase was probably caused by microbial action. Addition of salt to spoiled fish seemed to inhibit microbial action, thus suppressing the formation of VFAs. The contents of short and long straight chain VFAs in aerobically fermented sauces were significantly higher than in anaerobically fermented sauces, suggesting that straight chain VFAs developed from fish fats. Certain branched VFAs were derived from the degradation of specific amino acids, such as isobutyric acid from valine and isovaleric acid from leucine. Alanine and isoleucine did not have a clear influence on the production of VFAs. © 2001 Society of Chemical Industry     

Use of bacterial extracts to enhance amino acid breakdown in dry fermented sausages

The effect of the intracellular cell-free extracts (ICFEs) of two bacterial strains (Lactobacillus sakei GO and Bacillus pumilus) on the amino acid catabolism and the sensory properties of dry fermented sausages, was investigated. Extracts were added to sausages alone or in combination with a protease, papain. Amino acid breakdown was monitored by the changes in free amino acids, ammonia and amine content during the ripening process. A 15% decrease in the content of free amino acids was observed in sausages added with the ICFE from L. sakei GO. Furthermore, the extract of L. sakei GO significantly reduced (54-68%) the content of the amino acids considered as precursors of the typical ripened flavour, i.e., valine, leucine and isoleucine. Chemical changes were not reflected in a significant improvement of the sensory quality of sausages added with the ICFEs. The potential use of the bacterial ICFEs studied in the present work for the manufacture of dry fermented sausages, and its comparison with the use of fungal extracts, are discussed.     

前体氨基酸对赤霞珠干红葡萄酒中生物胺含量的影响

以新疆地产赤霞珠果实为原料,在葡萄汁中分别加入不同浓度的7种前体氨基酸,进行酒精发酵与苹果酸-乳酸发酵。通过高效液相色谱法的分析检测,了解前体氨基酸对葡萄酒中8种生物胺含量的影响。结果表明,前体氨基酸对葡萄酒中生物胺的含量产生一定的影响,当加入质量浓度为40 mg/L和100 mg/L的组氨酸时,组胺含量由1.04 mg/L减少为0.20 mg/L和0.35 mg/L;而当加入色氨酸、精氨酸和鸟氨酸时,会使色胺和腐胺的含量有所降低,当加入300 mg/L质量浓度的精氨酸时,腐胺含量由1.45 mg/L减少至0.63 mg/L。当葡萄酒中加入同一种氨基酸时,对葡萄酒中不同的生物胺含量的影响也不尽相同。     

碱性和支链氨基酸对啤酒高浓酿造酵母发酵性能的影响

研究分别考察添加三种碱性氨基酸：精氨酸（Arg）、赖氨酸（Lys）、组氨酸（His）与支链氨基酸：缬氨酸（Val）、亮氨酸（Leu）、异亮氨酸（Ile）对24 °P高浓酿造过程中酵母发酵性能及啤酒风味的影响。结果表明,六种氨基酸的添加可促进酵母生长并提高活细胞率,显著提高麦汁发酵度及乙醇产量。其中,添加Val、Leu与Arg的高浓麦汁发酵性能较好,与对照组相比,发酵结束时总CO2失质量分别为92.4 g/L、92.7 g/L与91.2 g/L;发酵度极显著提高（P＜0.01）,分别为83.65%、82.95%和82.93%;乙醇产量极显著提高（P＜0.01）,分别为11.97%（V/V）、11.90%（V/V）和11.83%（V/V）。添加Arg可显著提高酵母总细胞数（1.64×108 cells/mL）（P＜0.05）,His、Val与Leu的添加对风味物质影响较大,可提高啤酒的醇酯比,其中,Val的添加可显著提高异丁醇含量（P＜0.05）,降低总酯含量;Leu的添加则可同时提高异戊醇及乙酸异戊酯的含量。     

陈酿期间无花果酒风味品质的变化

陈酿是提升果酒品质的一种重要手段。研究基于无花果酒的挥发性风味物质、游离氨基酸含量和感官特性,以0、2、4、6个月的陈酿无花果酒为研究对象,探究陈酿对无花果酒风味的影响。结果表明,随着陈酿时间的延长,酯类和醛类物质种类及相对含量均有所增加,然而醇类和酸类物质种类及相对含量均下降。电子鼻结果显示,陈酿0、2、4个月对果酒风味影响有明显区别,第4个月是风味变化的平衡点。陈酿过程中,无花果酒游离氨基酸总量和甜味氨基酸（苏氨酸、丝氨酸、脯氨酸、甘氨酸、丙氨酸、蛋氨酸、精氨酸）含量在第4个月达到最高值后呈现下降趋势,苦味氨基酸（缬氨酸、异亮氨酸、亮氨酸、酪氨酸、苯丙氨酸、赖氨酸、组氨酸）含量显著下降（P＜0.05）,鲜味氨基酸（天冬氨酸、谷氨酸）含量显著上升（P＜0.05）。皮尔森相关性分析方法进一步确证,陈酿通过提升澄清度、增加酯类和醛类化合物、释放鲜甜味氨基酸,以平衡果酒香气口感、提升风味品质。