Implications of nitrogen compounds during alcoholic fermentation from some grape varieties at different maturation stages and cultivation systems

The aim of this work was to study the influence of grape variety, cultivation system and stage of grape maturation on nitrogen compounds evolution during alcoholic fermentation. To do this, four grape varieties, Monastrell, Merlot, Syrah and Petit Verdot, traditionally cultivated and Monastrell cultivated using organic agriculture, which were collected in two different stages of maturation, were used. The results showed that, regardless of grape variety, cultivation system and stage of grape maturation, the consumption of nitrogen compounds was directly proportional (R² > 0.7) to their concentration in natural musts. This is very important as it is the first time that these results were obtained with natural musts without external addition of nitrogen compounds.     

可同化氮含量对赤霞珠葡萄酒发酵和香气成分的影响

选取山西戎子酒庄有限公司不同位置的三个葡萄园(驮腰坡,东廒北,东廒南),对各葡萄园进行土壤含氮量、赤霞珠葡萄及葡萄酒发酵过程中可同化氮(YAN)含量、葡萄酒理化指标与香气成分的检测分析。结果表明,葡萄果实可同化氮含量可能主要与土壤铵态氮含量有关。不同葡萄园的赤霞珠葡萄汁可同化氮的含量不同,均超过了150 mg/L,能保证发酵顺利进行。如果需要添加可同化氮时,应以此时测定的可同化氮含量为依据,避免添加过量。原酒中酯类和醇类相对含量由高到低依次为：驮腰坡＞东廒南助剂＞东廒北＞东廒南,这与葡萄汁中可同化氮含量呈正相关。     

Free amino acids and volatile compounds in vinegars obtained from different types of substrate

The present work reports on the free amino acids and volatile compounds in vinegars obtained from different types of raw materials (cider, white wine and red wine). Based on the amino acid contents of three types of vinegar and of the substrates from which they were obtained, the profile of the nitrogen‐supplying compounds and their uptake for the acetic acid bacteria were very similar. The most important amino acid in terms of supply and uptake was found to be L ‐leucine. L ‐Proline proved also important in the wine vinegars, however it was not depleted as L ‐leucine. The different acetification reactions involved were found to yield acetoin, and plus 1,1‐diethoxyethane in the wine vinegars. Copyright © 2004 Society of Chemical Industry     

蛇龙珠新品系葡萄酒香气成分分析及评价

采用固相微萃取（SPME）结合气相色谱-质谱联用（GC-MS）检测技术比较分析了烟台地区8个蛇龙珠新品系（编号为E-01～E-08）的香气差异。结果表明，8个蛇龙珠新品系共检测出70种挥发性物质，其中，酯类19种，醇类10种，酸类10种，醛酮类6种，萜烯类5种，芳香族7种，硫化物1种，C13-降异戊二烯类2种，内酯类1种，酚类9种。经气味活性值（OAV）鉴定出16种对葡萄酒香气有积极作用的活性香气成分（OAV＞1）。隶属函数值分析比较表明，蛇龙珠新品系当中，品种E-04香气表现最好，其次是品种E-01、E-03。     

绵羊、牛和猪脂肪组织中挥发性脂肪酸的组成分析

为了研究不同畜种之间脂肪组织中挥发性脂肪酸的组成成分,利用同时蒸馏萃取技术和气相色谱技术对猪、牛和羊脂肪组织中的挥发性脂肪酸进行了测定.结果表明,绵羊、牛和猪脂肪组织中总挥发性脂肪酸分别为600.512、456.029、202.371 mg/kg.在猪脂肪组织中没有检测到支链脂肪酸;在牛脂肪组织中检测到了4-甲基辛酸,质量比为7.508 mg/kg,远小于羊脂肪组织中4-甲基辛酸的含量,其质量比为28.119 mg/kg;在羊脂肪组织中,检测到种类较为丰富的挥发性脂肪酸,其中对羊肉膻味起主要作用的4-甲基辛酸,在羊脂肪组织中有较高的含量,这一特征与猪和牛的挥发性脂肪酸形成显著的区别.     

Addition of amino acids to grape juice of the Merlot variety: Effect on amino acid uptake and aroma generation during alcoholic fermentation

The effects of adding selected amino acids (phenylalanine, alanine, aspartic acid and threonine) to grape juice on the generation of aroma compounds and on amino acid uptake were studied. The fermentation kinetics varied according to the quantities of amino acids added. The fermentations finished more quickly in supplemented juices and their alcoholic content was significantly higher than in the control (p < 0.05). Amino acids were consumed mainly in the first quarter of fermentation. Higher alcohol formation took place at the same time as ethanol formation: with more amino acids present in the medium, more phenyl ethanol (p = 0.01) and benzyl alcohol were formed while isoamyl alcohol production decreased. The contents of isoamyl and phenylethyl acetates, ethyl hexanoate and ethyl octanoate, as well as most fatty acids increased during the fermentation, reaching a maximum for 10% of ethanol; with higher alcoholic contents, their concentrations decreased.     

南宁地区米酒曲中酵母菌的分离鉴定及其在红枣酒中的应用

从采自南宁地区的米酒曲中分离酵母菌并进行鉴定,同时选取鉴定为扣囊复膜酵母（Saccharomycopsis fibuligera）和酿酒酵母（Saccharomyces cerevisiae）的分离株进行了红枣酒制备,并采用氨基酸分析仪和气相色谱-质谱联用（GC-MS）仪对其氨基酸和挥发性风味物质的种类及含量进行了评价。结果表明,从米酒曲中分离出的酵母菌被鉴定为5个属的5个种,且以S. fibuligera为优势菌株,占分离株总数的50%。红枣酒中含量较多的氨基酸为脯氨酸和天冬氨酸,平均含量分别为1 857.93 mg/L和771.59 mg/L,而呈味氨基酸主要以甘味和酸味呈味氨基酸为主,占氨基酸总量的68.2%和23.6%。异戊醇和乙酸乙酯为红枣酒中主要挥发性风味物质,平均相对含量为33.03%和24.37%。     

Contents of 3‐alkyl‐2‐methoxypyrazines in musts and wines from Vitis vinifera variety Cabernet Sauvignon: influence of irrigation and plantation density

The influence of irrigation and plantation density on the methoxypyrazine content in musts and wines has been studied. Samples were monitored throughout grape ripening and wine‐making. 3‐Isobutyl‐2‐methoxypyrazine, 3‐sec‐butyl‐2‐methoxypyrazine and 3‐isopropyl‐2‐methoxypyrazine were identified and quantified. Samples from irrigated vines had significantly higher average contents of 3‐isobutyl‐2‐methoxypyrazine than samples from non‐irrigated plants. Average levels of this compound were also higher in samples from vines with the higher plantation density. Copyright © 2005 Society of Chemical Industry     

Volatile compounds of experimental liver pâté from pigs fed conjugated linoleic acid in combination with monounsaturated fatty acids

BACKGROUND: Feeding conjugated linoleic acid (CLA) to pigs leads to CLA‐enriched meat products, which are of current interest owing to the potential health properties of CLA. However, dietary CLA increases the ratio of saturated to monounsaturated fatty acids (MUFA) in pig tissues. Combining CLA with high MUFA levels in pig diets may counteract this effect. Owing to the modification of fatty acid composition, variation in the volatile profile of derived meat products might be expected. The aim of the present work was to study the volatile profile, and its change during storage, of experimental liver pâté manufactured from pigs fed different levels of CLA and MUFA. RESULTS: Regardless of the CLA or MUFA level, 98 compounds were identified. Lower area units were observed for most branched aldehydes, ketones and alcohols and some furans, sulfur compounds and nitrogen compounds with increasing CLA and MUFA contents. Levels of nonanal, propan‐2‐one, dodecane, 2‐pentylfuran and ethylbenzene were higher in CLA pâtes. The effect of experimental diets on the change in volatiles during storage was not significant. CONCLUSION: Supplementation of pig diets with CLA isomers in combination with low or high MUFA levels seems to have a significant effect on the volatile profile of pork liver pâté. Copyright © 2009 Society of Chemical Industry     

Carbon and nitrogen partitioning in either fruiting or non-fruiting grapevines: effects of nitrogen limitation before and after veraison

Fruit effects on carbon (C) balance between reproductive and vegetative growth, and between shoots and roots, were studied under low versus high nitrogen (N) availability before and after veraison. Fruiting vines were compared with non-fruiting vines, and N was supplied at either a low or high rate, and either continuously or as a split application before and after veraison. In non-fruiting grapevines, leaf growth was greatly affected by N supply, but root growth was little affected. Low N supply before veraison favoured berry development, whereas after veraison enlarging fruits were disadvantaged by low N supply. Fruit growth was highly competitive with root growth, particularly before veraison, when N supply was low. Whole plant C and N accumulation rates were lower in fruiting plants. Berry amino acid content was influenced by all combinations of N treatments. Overall, fruit development was favoured by ensuring a low N supply rate before veraison, but this occurred at the expense of root growth as well as C and N uptake by the grapevines. After veraison, fruit can express a high sink strength if N is made available, probably because photosynthetic activity increases. These results provide new insights into how N may be managed in order to control grapevine C partitioning, to encourage berry development, and to sustain overall C and N uptake by grapevines.     

The development of free amino acids and volatile compounds in cheese ‘Oloumoucké tvarůžky’ (PGI) during ripening

Twenty‐two free amino acid (FAA) concentrations were observed during manufacture (7 days) and ripening period (42 days follow‐up) of Olomoucké tvar??ky (PGI, smear acid cheese). During the ripening period, the amounts of volatile compounds and selected sensory attributes were also analysed. The free amino acids were determined by means of ion‐exchange chromatography, and the volatile compounds were detected and identified using HS‐SPME coupled with GC/MS method. The development of the individual FAA content positively correlated with the ripening period (r = 0.7734–0.9229; P < 0.01). Forty‐six volatile compounds (14 alcohols; 10 esters; 7 ketones; 5 acids; 4 aldehydes; 3 sulphur compounds; 2 phenol compounds; and 1 terpene) were identified. Concentrations of several compounds increased (e.g. 3‐methylbutanal, 2‐butanol, 2‐butanone; P < 0.05) or decreased (e.g. dimethyldisulphide, methanethiol, 2‐phenylethylacetate, methylbutyric acid; P < 0.05) over cheese ageing. The results gave information about the development of sensory active substances and its precursors in Olomoucké tvar??ky during ripening. In conclusion, we found that free amino acid concentrations and sulphur compounds are positive with improved flavour.