Influence of fining agents on the sensorial characteristics and volatile composition of mead

Mead, one of the oldest fermented drinks, is derived from the fermentation of diluted honey by yeasts. In the context of wine production, several procedures are applied to stabilize the beverage and to improve its organoleptic properties. This study aims to evaluate the impact of adding fining agents on the production of mead. In general, the best results were obtained for the samples containing just one fining agent instead of two combined. However, the best performance was obtained for the combined fining agents (bentonite + gelatine + egg albumin). Tannins decreased significantly the content of volatile compounds. On the other hand, silica appears to be the best fining agent, resulting in the lowest loss of volatile compounds. Thirty‐six volatile compounds were determined by gas chromatograph–flame ionization detector and gas chromatography–mass spectrometry, including alcohols (42.5%), carbonyl compounds (40.4%), acetates (14.4%) and esters (1.8%). Eleven volatile compounds had odour activity values >1, representing those with a major impact on the aroma of mead. Significant differences (p  < 0.05) were found in 10 volatile compounds independently to the type of treatment used and no differences (p  > 0.05) were observed for remaining compounds. Copyright © 2017 The Institute of Brewing & Distilling     

Impact of fining agents on the volatile composition of sparkling mead

Sparkling mead is obtained by secondary fermentation of the mead involving the addition of starter yeast culture, sucrose, nutrients and fining agents. The aim of this study was to evaluate the effect of different fining agents (tannins vs combined fining agents) on the volatile composition of sparkling mead. Sparkling mead was produced from a base mead using a commercial yeast strain (Saccharomyces bayanus) and the volatile compounds were determined by gas chromatography–flame ionisation detection and gas chromatography–mass spectrometry. Thirty six volatile compounds were quantified and the major groups were alcohols (73.2%), acetates (19.1%), carbonyl compounds (5.5%) and ethyl esters (1.2%), represented by 3‐methyl‐1‐butanol, ethyl acetate, acetaldehyde and monoethyl succinate, respectively. The remaining compounds were present at <1%. Eleven volatile compounds exhibited odour activity values >1, with ethyl octanoate and ethyl hexanoate contributing to the aroma of sparkling mead, with fruity, strawberry and sweet notes. The combined fining agents caused a marked decrease in the concentration of volatile compounds compared with tannins. In general, 3‐ethoxy‐1‐propanol, ethyl lactate, ethyl octanoate, diethyl succinate, diethyl malate, monoethyl succinate, 2‐methylpropanoic acid, hexanoic acid, octanoic acid, acetaldehyde, acetoin, furfural, benzaldehyde, 5‐hydroxymethylfurfural, trans‐furan linalool oxide, cis‐furan linalool oxide and 4‐oxo‐isophorone decreased in concentration. Conversely, 1‐propanol and 2‐methylpropanoic acid (tannins) and ethyl butyrate (combined fining agents) increased in concentration. The remaining volatile compounds were not affected. Significant differences (p < 0.05) were found for 19 volatile compounds independently of the type of fining agents used. © 2018 The Institute of Brewing & Distilling     

Comparison of fining red wines with purified grape pomace versus commercial fining agents: effect on wine chromatic characteristics and phenolic content

The large quantity of grape pomace (seeds, skin, and peduncle) produced during the winemaking process can be a problem and the search for procedures which could permit their valorisation is considered an important issue. This study investigates the use of purified grape pomace as a fining agent for reducing the level of some wine phenolic compounds, especially tannins. For this, purified grape pomace was applied to three young red wines of different phenolic composition and the results were compared with the effect of some common commercial fining agents. The results demonstrated that grape pomace can be used to decrease the wine tannin content with similar results to those obtained with casein, while also reducing anthocyanin content although to a similar extent to when bentonite is used. The effect of purified Monastrell grapes pomace is similar in the three different studied wines although it affected the most to wines with high monomeric anthocyanin content.     

橡木提取液对霞多丽和赤霞珠葡萄果实品质的影响

主要研究橡木提取液对葡萄果实品质的影响。以欧亚种（Vitis vinifera L.）酿酒葡萄品种赤霞珠和霞多 丽为实验材料,外源喷施橡木提取液后测定果实单宁、多酚、花色苷、单糖和有机酸单体含量及香气成分的质量 浓度。结果表明：橡木提取液对葡萄果实基本理化性质影响不显著,橡木提取液可提高霞多丽果实总酚和单宁含 量,其中体积分数25%美国橡木提取液处理组单宁含量比对照组（喷蒸馏水,下同）增加了33.2%;橡木提取液可 提高赤霞珠果实单宁和总花色苷含量,与对照组相比,体积分数25%美国橡木提取液处理后赤霞珠单宁含量增加 了40.7%,纯美国橡木提取液处理后花色苷含量增加了10.7%;纯橡木提取液可以提高霞多丽和赤霞珠果实果糖含 量;橡木提取液可以提高霞多丽和赤霞珠果实葡萄糖含量。橡木提取液对霞多丽和赤霞珠果实香气成分有很大影 响,都增加了果实香气成分的种类,尤其是酯类、醛类和醇类（如橡木内酯、四氢薰衣草醇）,同时可增加果实香 气质量浓度,如体积分数25%美国橡木提取液可使6-甲氧基丁子香酚的质量浓度增加近8 倍。外源喷施橡木提取液 可改善葡萄果实品质,结果可为葡萄产业废弃物开发利用提供理论依据。     

Impact of wine manufacturing practice on the occurrence of fining agents with allergenic potential

Proteinogenic wine fining agents are hidden allergens and could present a risk for consumers with allergies. Therefore, the European Parliament adopted Directive 2003/89/EC amending Directive 2000/13/EC to declare ingredients, contaminations and processing aids that are known to trigger allergic reactions. The Amendment Regulation (EU) 1266/2010 excluded the labelling of wines which are processed with hen’s egg and products thereof until 30 June 2012 to get more scientific findings. After 1 July 2012 wine fining agents have to be declared if above 0.25 mg l^–1 (Regulation (EU) 579/2012 in conjunction with article 120 g of Regulation (EU) 1234/2007). The Organisation International de la Vigne et du Vin (OIV) advises this limit of detection (LOD) for potential allergenic residues of proteins. Wine fining agents are processing aids and according to the wine producer’s knowledge will be removed after coagulation by filtration or other production steps. Due to lack of scientific data, residues of fining agents in the final product could not be excluded. In this risk assessment, highly sensitive ELISA methods for ovalbumin of known origin for wine have been developed. The objective was to investigate the presence of allergen residues in wine after certain technological treatments were applied to remove the wine fining agents. For all developed ELISA methods the LODs are in the low µg l^–1 range between 5 and 10 µg l^–1 fining agent, whereas the LOQ varies between 5 and 80 µg l^–1 fining agent. The results of the investigation of well-known wines and fining agents demonstrate that white wines fined with white or ovalbumin from hen’s egg could retain allergens. The use of certain technological procedures during wine processing leads to different results. In white wine, bentonite or sheet filtration followed by sterile filtration lead to wines containing no detectable amounts of ovalbumin. In red wine, especially the final sterile filtration removes the fining agents.     

The influence of skin contact during alcoholic fermentation on the aroma composition of Ribolla Gialla and Malvasia Istriana Vitis vinifera (L.) grape wines

Grapes from the Vitis vinifera (L.) varieties Ribolla Gialla and Malvasia Istriana were subjected to two skin contact procedures: pomace maceration and whole berry maceration during alcoholic fermentation. Wine free volatile compounds were determined using two extraction techniques coupled to GC; odour activity values were calculated and compared to control wines without skin contact. The highest concentrations of esters and relative fruity impacts were determined in the control wines for both varieties. Pomace maceration was found to be an effective procedure for the extraction of varietal aroma compounds like terpenes, but only in the Malvasia Istriana was their higher impact on floral odour determined. Pomace maceration resulted in higher total phenol and methanol content. Whole berry maceration was less efficient in terpene extraction, and its impact on general wine composition was not so radical. Control wines were chosen as preferred wines for odour and overall impression.     

Physicochemical characteristics and functional properties of grape (Vitis vinifera L.) seeds protein

The amino acid composition, physicochemical and functional properties of grape (Vitis vinifera L.) seeds protein (GSP) were evaluated and compared with those of soybean protein isolate (SPI). Amino acid analyses of GSP revealed high levels of glutamic/glutamine, glycine and aspartic/asparagines. SDS‐PAGE analysis demonstrated that globulin was the major protein component in GSP, whose subunit molecular weights were mainly varied from 25.5 to 40.0 kDa. The isoelectric pH of GSP was found to be at the acidic pH of around 3.8. At all the pHs tested except pH 2.0, no significant changes of GSP secondary structure were observed. GSP exhibited beneficial functional properties such as preferable solubility and emulsifying activity, while the foaming properties and water holding capacity were relatively poor compared to SPI. It could then be employed to soup, sauce, beverage or meat product for improving nutritional and sensory quality of these foods at appropriate pHs.     

Effects of defoliation on quality attributes of Nero di Troia (Vitis vinifera L.) grape and wine

Field studies were conducted in Puglia (Italy) to evaluate the influence of defoliation around cluster zones on grape and wine quality. Nero di Troia grapes were subjected to four different treatments: N: no leaf removal; E: leaf removal in the area of the clusters along the east side (at complete veraison); E/W: leaf removal in the area of the clusters along the east and west side (at complete veraison); and F: almost complete leaf removal along the west side (at complete veraison) and at pre-harvest also along the east side. Grapes of defoliated vines generally showed higher sugar content, lower titratable acidity, total flavonoids, flavonoids different from anthocyanins, and total phenolic content than grapes from non-defoliated vines while their total anthocyanin concentration was not affected by defoliation at a significant level. Concerning wines, alcohol content, residual soluble solids, different forms of anthocyanins but also volatile acidity were generally higher in samples from defoliated vines. Differences were also highlighted among the defoliation treatments: the best results in terms of dry matter, sugar and alcohol content were observed in the samples submitted to the more severe defoliation as a consequence of the higher light availability and berry temperature. Concerning the concentration of the individual phenolics, significant differences were highlighted for: caffeic and caftaric acids, peonidin- and malvidin-3-p-coumaroylglucoside, which were higher in the E wines; quercetin-3-glucoside, galactoside, and rhamnoside, and procyanidins, which were higher in F wines.     

A Novel Process for the Recovery of Polyphenols from Grape (Vitis vinifera L.) Pomace

ABSTRACT: A novel process for enzyme-assisted extraction of polyphenols from winery by-products was established on a pilot-plant scale. Optimization of enzymatic hydrolysis of grape skins, that is, selection of pectinolytic and cellulolytic enzymes, enzyme-substrate ratio, and time-temperature regime of enzymatic treatment, was conducted on a laboratory scale. Enzyme activities were monitored by viscosity measurement of resuspended grape pomace and by quantification of oligomeric pectin and cellulose degradation products released from cell wall material. Optimal conditions were obtained with 5000 ppm (based on dry matter) of a pectinolytic and 2500 ppm of a cellulolytic enzyme preparation, respectively, at 50°C, which were also applied in pilot-plant scale experiments. Concomitant determination of individual polyphenolics demonstrated a significantly improved yield for most compounds when compared with experiments without enzyme addition. Recovery rates were comparable to those obtained when grape pomace was extracted using sulfite. Pre-extraction of the pomace with hot water followed by treatment with cell wall degrading enzymes even increased yields of phenolic compounds. Only some quercetin glycosides and malvidin coumaroylglucoside were partly hydrolyzed due to enzyme side activities. This new process may provide a valuable alternative to the application of sulfite, which is considered crucial in food processing.     

Effect of terroir on the volatiles of Vitis vinifera cv. Albariño

The effect of terroir on volatiles of Vitis vinifera cv Albariño was studied. Twelve commercial Albariño wines from Galicia, Spain, were analysed. The content of varietals and fermentative volatile compounds was determined by gas chromatography. The numerous significant differences found for most of the aromatic compounds studied show the influence of the terroir. The Albariño wines from northern Galicia showed the highest total concentration of volatiles analysed. The volatile components showing the greatest differences in Albariño wines from different areas were terpenes and higher alcohols. Among the terpenes found, geraniol was markedly abundant in the north, while nerol and linalool were most abundant in the south. Among the alcohols, 2‐phenyl ethanol and benzyl alcohol showed the highest concentrations in the south and in the north, respectively. Cluster analysis and principal component analysis revealed two clearly defined main groups of Albariño wines from different terroirs. Albariño wines from the south were more heterogenic than those of the north. Copyright © 2007 Society of Chemical Industry     

Effect of foliar nitrogen and sulfur on petit manseng (Vitis vinifera L.) grape composition

Vineyard applications of foliar nitrogen (N) and sulfur were evaluated in the Yadkin Valley of North Carolina in 2011 and 2012 as a means to modify grape composition of Vitis vinifera cv. petit manseng. Four treatments were applied each year in a randomized complete block design with six replicates of six vines each: untreated control, soil N at 30?kg/ha, foliar N at 15?kg/ha and foliar N at 15?kg/ha plus sulfur at 5?kg/ha. Fruit ammonia and yeast assimilable nitrogen (YAN) concentrations increased in foliar-treated vines both seasons compared to control vines. Total glycosides (TGGs) increased ～80% in foliar N/sulfur-treated vines compared to control vines in 2011, and TGGs increased ～157% in foliar N/sulfur-treated vines relative to glycoside level in foliar N alone in 2012. Foliar N and foliar N/sulfur applications increased the majority of amino acid concentrations analyzed in 2011. Measured concentrations of various amino acids, partly responsible for aroma and flavor of petit manseng wines, were differentially dependent on the method of N application. Foliar applied nitrogen may be an effective technique to contribute to berry composition optimization of petit manseng grown in a warm, humid climate.     

避雨栽培条件下红宝石无核葡萄光合特性初探

以欧亚种葡萄红宝石无核为试材,使用LI-6400光合作用测定系统,对其在避雨栽培条件下果实膨大期的光合特性进行了研究.结果表明:葡萄叶片的净光合速率(Pn)日变化呈双峰曲线,具有明显的光合"午休"现象.光饱和点(LSP)为1500цmol/(m2·s),光补偿点(LCP)为55.48 u mol(m2·s); C02饱和点(CSP)为1200 u mol/mol,CO2补偿点(CCP)为45.04 u mol/mol;表观量子效率(AQY)为0.0436,羧化效率(CE)为0.0461.     

Effects of mechanical thinning on fruit and wine composition and sensory attributes of Grenache and Tempranillo varieties (Vitis vinifera L.)

Background and Aims: Cost-effective yield control is required by the wine industry in order to reduce the existing worldwide wine surplus and to improve grape quality. The object of this study was to evaluate the chemical and sensory effects on the resulting wines of mechanical cluster thinning performed at different intensities on Grenache, and at different timings (pea size and veraison) on Tempranillo. Methods and Results: The experiments were conducted with a machine harvester in 2007 on two commercial vertical shoot-positioned vineyards in Spain's Rioja region. In both varieties, mechanical thinning was effective in yield reduction and resulted in more ripened fruit, and wines with higher alcohol and pH values, more intense colour and increased phenolic content. Regardless of the thinning intensity, sensory changes were less noticeable in Grenache than in Tempranillo wines. Of the latter, those from vines thinned during veraison were less aromatic and sour, but had increased astringency. Conclusions: Yield management through mechanical thinning induced changes to the chemical composition of fruit and wines as well as to the wines' aroma, taste and mouthfeel. The extent of the sensory implications seems to depend on several factors such as the variety and timing of thinning application. Significance of the Study: This is one of the first studies addressing the effects of mechanical thinning on the sensory properties of the resulting wine and has implications for viticultural management practices.     

浸渍酶对蛇龙珠葡萄酒酿造过程中类黄酮化合物变化的影响

研究了浸渍酶Lallzyme Ex-V对蛇龙珠葡萄酒酿造过程中(从酒精发酵到橡木桶贮藏12个月)类黄酮动态变化的影响。结果显示,经浸渍酶处理加快了儿茶素、表儿茶素、杨梅素、山奈酚和槲皮素等5种类黄酮化合物在葡萄酒酒精发酵期间的浸提速度,但不影响杨梅素和槲皮素在后续酿造过程中的含量,杨梅素在葡萄酒酒精发酵结束后含量逐步下降,槲皮素在橡木桶陈酿期间含量逐渐增加;酶处理对儿茶素和表儿茶素的影响一直持续到苹-乳发酵的第2周,酶处理酒中儿茶素和表儿茶素的含量高于对照;浸渍酶对山奈酚含量的影响一直持续到橡木桶陈酿3个月,处理酒中的含量高于对照。