Release of wine monoterpenes from natural precursors by glycosidases from Oenococcus oeni

It is now well established that wine-related lactic acid bacteria (LAB), especially Oenococcus oeni, possess glycosidase activities that positively contribute to wine aroma through the hydrolysis of grape-derived aroma precursors. In our recent studies, we have identified and characterised several LAB glycosidases with potential in these terms. Here, we report that both a glucosidase and an arabinosidase from O. oeni can release high amounts of monoterpenes from natural substrates under optimal conditions, indicating that these intracellular enzymes might play a significant role in the hydrolysis of aroma precursors during malolactic fermentation. The enzymes from O. oeni exhibited broad substrate specificities (release of both primary/tertiary terpene alcohols) and were even active in grape juice. Further, a sensory panel clearly preferred enzyme-treated Riesling wines over the controls and affirmed that the glycosidases from O. oeni could improve the typical Riesling aroma.     

Enhancement of volatile aromatic compounds in black raspberry wines via enzymatic treatment

Robus coreanus Miquel is widely used in the production of Korean black raspberry (KBR) wine owing to its health benefits and commercial value. The effects of three different commercially available glycosidase enzymes on the volatile compounds in KBR wines were investigated with large‐scale fermentation to develop a high‐flavour‐quality wine. Volatile aroma compounds from the wines were analysed using headspace‐solid phase micro‐extraction‐gas chromatography–mass spectrometry (HS‐SPME‐GC–MS) and sensory evaluations were performed to evaluate the flavour characteristics. KBR wines treated with commercial enzymes yielded high concentrations of terpenes and esters compared with the control wine because the odourless non‐volatile glycosides in KBR wines were converted to their corresponding free forms by the enzymes. HS‐SPME‐GC–MS‐SIM analysis showed that the primary monoterpene compounds in KBR wines treated by the enzymes were myrtenol, linalool, citronellol and a significant quantity of compounds such as 2‐phenyl ethanol and ethyl benzoate, which contributed to the flavour of KBR wine, as determined by GC‐FID. KBR wines treated with the enzymes exhibited different sensory characteristics from the control wine owing to higher intensity of floral and fruity aromas. KBR wine treated with CYTOLASE PCL5 on a large scale exhibited the highest sensory preference. Copyright © 2017 The Institute of Brewing & Distilling     

Potential of Glycosidase from Non‐Saccharomyces Isolates for Enhancement of Wine Aroma

The aim of this work was to rapidly screen indigenous yeasts with high levels of β‐glucosidase activity and assess the potential of glycosidase extracts for aroma enhancement in winemaking. A semiquantitative colorimetric assay was applied using 96‐well plates to screen yeasts from 3 different regions of China. Isolates with high β‐glucosidase activity were confirmed by the commonly used pNP assay. Among 493 non‐Saccharomyces isolates belonging to 8 generas, 3 isolates were selected for their high levels of β‐glucosidase activity and were identified as Hanseniaspora uvarum, Pichia membranifaciens, and Rhodotorula mucilaginosa by sequence analysis of the 26S rDNA D1/D2 domain. β‐Glucosidase in the glycosidase extract from H. uvarum strain showed the highest activity in winemaking conditions among the selected isolates. For aroma enhancement in winemaking, the glycosidase extract from H. uvarum strain exhibited catalytic specificity for aromatic glycosides of C₁₃‐norisoprenoids and some terpenes, enhancing fresh floral, sweet, berry, and nutty aroma characteristics in wine.     

Simulation of retronasal aroma of white and red wine in a model mouth system. Investigating the influence of saliva on volatile compound concentrations

The influence of saliva on aroma release from white and red wines was studied in a model mouth system. Aroma compounds were analysed in the dynamic headspace of wines by solid phase micro extraction/gas chromatography with flame ionization detection. Volatile compounds were identified by solid phase micro extraction/gas chromatography-mass spectrometry, resulting in a total of 43 compounds in white wine and 41 in red wine. The results showed a greater influence of saliva on aroma release in white wine than red wine. In white wine treated with human saliva, esters and fusel alcohols, responsible for fruity and fusel oil odours, were reduced of 32–80%; by contrast, the concentration of 2-phenylethanol and furfural, responsible for rose and toasted almond notes, increased by 27% and by 155%, respectively. In red wine, treated with human saliva, only a few esters decrease, with a reduction of 22–51% due to protein-binding ability of polyphenols that are able to inhibit the activity of the saliva. C-13 norisoprenoids, vitispirane (eucalyptol) and TDN (kerosene), decreased both in white and red wine, showing a comparable variation while, for β-damascenone, the variation was insignificant.     

Volatile composition of wines from cvs. Blanco lexítimo,Agudelo and Serradelo (Vitis vinifera) grown in Betanzos (NW Spain)

Wine aroma is formed by volatile compounds of different chemical natures and origins. Betanzos is the most northern viticole geographic area from Galicia (NW Spain). The aromatic profiles of wines produced from two white varieties (Blanco lexítimo and Agudelo) and one red variety (Serradelo) from Betanzos, harvested in 2006 and 2007, have been established by gas chromatography (GC/FID). A total of 35 varietal and fermentative aroma compounds were identified and quantified in free volatile form, which include terpenols, C₁₃‐norisoprenoids, alcohols, esters, volatile fatty acids and volatile phenols. To ascertain the compounds with major impact odours, the Odour Activity Value (OAV) was calculated. Twelve compounds showed concentrations above their perception threshold (OAV>1). The results obtained suggest that ethyl octanoate (apple), isoamyl acetate (banana), ethyl hexanoate (fruity) and β‐damascenone (floral) were the most powerful odorants for the white wines Blanco lexítimo and Agudelo from Betanzos. Ethyl octanoate and β‐damascenone (fruity and floral aroma respectively) were the most odorant for the red wine Serradelo.     

Aroma potential of Albillo wines and effect of skin-contact treatment

Free and glycosidically-bound aroma compounds were analysed in Albillo grape must, skin and wines, and the effects of different skin-contact treatments on aroma composition and wine sensory characteristics were evaluated. Musts and wines contained large amounts of C₆ and benzene compounds. Must skin contact, at 18 °C for 15 and 23 h, prompted a considerable increase in free and bound varietal compounds. Therefore, this technique, and the use of glycosidases are two methods recommended as a means for enhancing wine aroma. Skin-contact treatment intensified the fresh and fruity properties that were scored positively by wine tasters.     

FLAVOR AND AROMA ATTRIBUTES OF RIESLING WINES PRODUCED BY FREEZE CONCENTRATION AND MICROWAVE VACUUM DEHYDRATION

This article describes the production of sweet dessert wines produced using late‐harvest freeze concentration, wine produced from fresh grapes frozen using refrigeration and wine produced from grapes partially dried using microwave vacuum dehydration. The objective was to compare the aroma and flavor attributes of the wines to determine the effect of each method of juice concentration. The replicated wine samples were evaluated by 12 experienced judges, and the wines were analyzed using solid‐phase microextraction. The microextraction detected 28 compounds; however, levels of concentration of these compounds were below published aroma thresholds. Although all the wines were judged as acceptable sweet dessert wines, the judges detected significant differences. The wine made from the dehydrated grapes exhibited lower fresh fruit aroma, higher fusel oils and oxidation, and flavor notes including citrus/grapefruit and acidity were lower.     

Effects of Different β‐D‐Glycosidases on Bound Aroma Compounds in Muscat Grape Determined by HS‐SPME and GC‐MS

Important “floral” aromas naturally occur in grapes predominantly as flavourless glycoconjugate precursors. Since these aroma compounds can be released by hydrolysis, different glycosidase enzymes can potentially contribute different aromas to wines. In this paper, we first established a procedure for profiling the free and bound volatile compounds in grape using GC‐MS combined with headspace solid‐phase microextraction (HS‐SPME). Comparison of the free and bound aroma compounds revealed that non‐volatile glycosides, known as aroma precursors, occur in high concentrations in musts. Among all compounds identified, 11 were fully quantified according to established standard calibration curves, while others were semi‐quantified. Using three different glycosidase enzymes, a total of 38 bound volatile compounds were identified in Muscat grape, including terpenes, higher alcohols, C‐6 compounds, and phenols, among others. The different enzymes had significant effects on the varietal aroma. Principal component analysis indicated that the characteristic aroma hydrolyzed by the commercial enzyme AR2000 was clearly different from that produced by other enzymes.     

Synthesis of volatile phenols by Saccharomyces cerevisiae in wines

Vinylphenols (4-vinylphenol and 4-vinylguaiacol) are natural constituents of wine and can play a role in wine aroma. However, only white wines contain important quantities of these volatile substances which, beyond a certain concentration (limit threshold = 725 μg litre^?1 of 4-vinylguaiacol+4-vinylphenol (1:1)), can be responsible for a depreciating ‘phenolic’ or ‘pharmaceutic’ characteristic, Saccharomyces cerevisiae possesses a type-(E) enzymic activity, substituted cinnamate carboxy-lyase (SCD), which is capable of transforming, by non-oxidative decarboxylation, the phenolic acids in the must, (E) p-coumaric and (E) ferulic acids, into corresponding vinylphenols. This endocellular activity is constitutive, it is only expressed during alcoholic fermentation and with a variable intensity depending on the yeast strain. Furthermore, the enzyme is rapidly inhibited by catechic tannins, which explains why, in comparison with white wines, red and rosé wines contain low levels of vinylphenols despite having more precursors. A yeast strain with a weak SCD activity has been selected and its use in vinification should eliminate the appearance of the phenolic taint in white wines coming from grapes rich in decarboxylable hydroxycinnamic acids.     

The evaluation of remedial treatments for wine affected by Harmonia axyridis

This study evaluated the efficacy of a range of commercially available fining agents and other interventions on reducing 2‐isopropyl‐3‐methoxypyrazine (IPMP) concentration and taint characteristics of white and red wine affected by Harmonia axyridis (HA). Wines fermented in the presence of HA beetles were treated with bentonite, activated charcoal, oak chips, deodorized oak chips and either ultraviolet (red wine) or visible (white wine) light. IPMP concentrations were lowered by activated charcoal in white wine and deodorized oak in red wine. Treatment with oak chips reduced the intensity of HA‐associated sensory attributes (‘ladybug taint’) in both white and red wines, while other applications generally had no effect on white wine and limited effect on red wines.     

Investigation on the role played by fermentation esters in the aroma of young Spanish wines by multivariate analysis

The role played by ethyl esters of fatty acids and by acetates of higher alcohols on the aroma of young wines from neutral grape varieties has been investigated. The statistical methods used have been stepwise linear regression and principal components analysis. Very significant conclusions have been reached. The role played by these compounds depends on the type of wine. In white wines their main role is in the perception of tree fruit and tropical fruit notes. It has been demonstrated that the former notes are linked to ethyl esters, while the latter are linked mainly to acetates of higher alcohols. In rose wines the intensity of tree fruit aroma was correlated with ester content, however no clear conclusion was reached about the role of various compounds on the perception of quality. Finally, in red wines these compounds do not determine the intensity of fruit aromas, and they only play a modulating role on aroma quality. This indicates that red grape varieties must have other aroma compounds which are responsible for the fruity characteristics of wines.     

Effect of saliva esterase activity on ester solutions and possible consequences for the in‐mouth ester release during wine intake

The aim of this study was to investigate the role of saliva esterase activity on carboxylic esters typically associated with pleasant and fruity aromas in wine. For this, ex vivo experiments using the same fresh and inactivated (without enzymatic activity) human saliva with a mixture of carboxylic esters with different aliphatic chain length (ethyl butanoate, ethyl pentanoate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and isoamyl acetate) were prepared. Liquid–liquid extraction with dichloromethane and GC–MS analysis were applied to the saliva systems in order to determine the reduction in ester content and the formation of their corresponding metabolic products (carboxylic acids) in the saliva systems before and after incubation at 37C. In addition, to check if there was a relationship between the susceptibility of esters to saliva hydrolysis and the amount of in‐mouth ester release during wine intake, the remaining oral amount of each ester was determined by comparing the intraoral amount immediately after spitting out the wine and 4 min later. Ex vivo experiments showed ester degradation by saliva esterase enzymes mainly acted on long chain esters (ethyl octanoate and ethyl decanoate), which gave rise to the formation of their corresponding carboxylic acids. Nonetheless, in spite of their higher susceptibility to saliva enzymes, in vivo experiments showed that long chain carboxylic esters remained in the oral cavity long after swallowing. This confirmed that ester hydrophobicity is closely related to the in‐mouth temporal release of these odorants and, therefore, behind wine aroma persistence. In wines, esters represent a group of aromatic compounds of great interest since they are linked to pleasant fruity aroma nuances. Today wine consumers are demanding fresh and long persistent fruity aromatic wines. The present research contributes to better understanding the relationship between ester content in the wine and oral aroma release experienced during wine tasting, considering the changes in these compounds during oral processing. This is a necessary step when trying to unravel the factors involved in wine aroma perception and in consumer preferences, and it represents a necessary knowledge in promoting winemaking practices (e.g., the use of selected microorganisms) for improving the type and amount of these aroma compounds in the wine.     

The chemical and sensorial effects of lysozyme addition to red and white wines over six months' cellar storage

Lysozyme is an enzyme with muramidase activity which can lyse Gram-positive bacteria, including wine lactic acid bacteria. This enzyme provides a practical method for delaying or preventing the growth of Oenococcus oeni and consequently the onset of malolactic fermentation during the vinification of red and white wines. This paper reports the impact of lysozyme on the chemical and sensorial properties of commercially vinified red (Cabernet Sauvignon and Shiraz) and white (Riesling) wines. The addition of lysozyme to these wines had little or no effect on the content of alcohol, free and total sulfur dioxide and titratable acidity, and pH value. The lysozyme retained 75–80% activity in the Riesling wine after six months, however no detectable activity remained in the Cabernet Sauvignon and Shiraz wines after two days. Upon addition of lysozyme to both of the red wines, a rapid initial decrease (up to 17%) in red wine colour density and phenolic content occurred in association with the formation of a light precipitate. The reduction in red wine colour was also noted by the sensory panel. When added to the Riesling wine, lysozyme did not cause an increase in browning over the six month storage time, but did induce heat instability (haze), suggesting that white wines may require protein stabilisation following treatment with lysozyme. Sensory assessment by triangle difference testing revealed that, during the six month storage period, treatment with lysozyme did not cause important changes to either the aroma or palate of the red and white wines tested.     

Flavonol composition of Australian red and white wines determined by high‐performance liquid chromatography

Background and Aims: Flavonols are present in Vitis vinifera L. wine grapes as glycosides and are found in wines in both their glycosidic and aglycone forms. Flavonols and their glycosides are important components in wine because of their impact on colour, taste and health properties. An assessment of the flavonols and flavonol glycosides present in a wide selection of Australian red and white wines (n = 121 and 44, respectively) was undertaken. Methods and Results: Analyses were performed using HPLC, with compound identification being aided by HPLC‐MS. In the red wines, quercetin and myricetin dominated the flavonol profile, and quercetin‐3‐glucuronide was by far the most abundant glycoside present. White wines had considerably lower levels of flavonols and their glycosides, in most cases, being below the detection limit of the HPLC method. Conclusions: There appeared to be no correlation between the flavonol profile and wine variety or region in either white or red wines. Contrary to literature reports of rutin in wine, rutin was not found in any of the wines we analysed, and spiking experiments showed rutin rapidly degraded to the aglycone quercetin. Furthermore, changes in elution order for some quercetin glycoside standards were observed depending upon the acid used in the mobile phase. Significance of the Study: This is the first time the flavonol contents of an extensive cross section of Australian wines have been reported. The concentrations are consistent with those reported in wines from other countries. In light of the instability of rutin in wine, critical review should be given to reports discussing its presence.     

Influence of Visual Masking Technique on the Assessment of 2 Red Wines by Trained and Consumer Assessors

ABSTRACT:  During sensory evaluation assessments, visual masking techniques are frequently employed to disguise color differences between samples and minimize perceptual bias. Particularly in wine, the impact of these masking techniques on panelist evaluations has not been well studied. The objective of this study was to study the influence of visual masking techniques on the aroma and flavor assessment of 2 red wines and observe the impact of these techniques on trained and consumer sensory panels. Specific masking techniques included (1) blue wine glass/white illumination; (2) clear glass/red illumination; and (3) clear glass/white illumination. Ten panelists were trained to recognize 7 aroma and flavor attributes, while consumer panelists ( n = 80) evaluated attributes and liking. For the trained panel, the visual masking technique affected only perceived spicy flavor of Syrah ( P ≤ 0.05), with the clear glass/red illumination resulting in more intense spicy flavor compared to the other 2 conditions. Principal components analysis showed that for the 2 red wines evaluated by the trained panel, red illumination resulted in higher spicy attributes and perceived astringency while wines served in blue wine glasses were higher in perceived astringency. For the consumer panel, red illumination resulted in wines higher in perceived astringency and blue wine glasses resulted in wines higher in perceived flavor liking. These results indicated that the visual masking techniques may influence both trained and consumer panel evaluation of aroma and flavor attributes of red wine. However, beyond red wine, this study makes the larger point that the choice of masking technique does impact sensory evaluations.     

中国主要葡萄酒产区酒酒球菌糖苷酶活性

在苹果酸乳酸发酵（malolactic fermentation,MLF）过程中,一些酒酒球菌产生的糖苷酶活性受葡萄酒环境的影响,筛选并利用在酿酒环境中具有高活力糖苷酶的菌株进行MLF,有助于提升葡萄酒的香气复杂性。本实验以中国5 个酿酒产区19 株酿酒特性优良的酒酒球菌和一株商业菌为实验菌株,通过测定5 种糖苷酶活性,对其中5 株糖苷酶活性高的菌株研究其在葡萄酒环境中糖苷酶的酶学性质。结果表明：20 株菌在相应底物作用下均含有可检测到的糖苷酶活力,不同菌株酶活性差异显著,地区间差异不显著。5 株糖苷酶活性高的菌株最适pH值为4.0,最适温度为45 ℃,在低水平（4%乙醇＋0.1 g/100 mL果糖）时有促进作用,高水平（14%乙醇＋2 g/100 mL果糖）时抑制作用显著,葡萄糖则表现为抑制作用,但各种酶活性表现为菌株依赖性。在模拟酒条件下,菌株相对酶活力仅是菌株酶活力的9.805%～32.331%。总之,在所选菌株中,SD-1f在葡萄酒环境中的糖苷酶活性最高。