Relationships between the varietal volatile composition of the musts and white wine aroma quality. A four year feasibility study

In this work, the harvest variability of the varietal composition of Fernão-Pires grape variety was evaluated using a dichloromethane liquid–liquid continuous extraction followed by GC-qMS of the free (F) and potential varietal components (PVC) from the musts across four harvests (1998, 1999, 2000, and 2002). This study showed that Fernão-Pires musts exhibited varietal volatile composition variability along the years. Based on the data obtained, using GC-qMS in tandem with PCA, relationships were established between the varietal volatile composition of the musts and the white wine aroma quality classification conferred by the official wine taster chamber. The results of the volatile analyses were consistent with the wine quality classification, indicating that the wine aroma quality is clearly associated with the musts free varietal volatile composition. On the other hand, the PVC fraction allowed the distinction of the musts according to the composition of potential aroma precursors. The proposed approach can provide information to winemakers concerning the winemaking methodologies that can be implemented to improve the varietal wine aroma quality.     

Contribution of free and glycosidically-bound volatile compounds to the aroma of muscat “a petit grains” wines and effect of skin contact

Free and glycosidically-bound volatile compounds of must, skin and wine from Muscat “a petit grains” cultivated in Spain were determined, and the effect of different skin contact times on the aroma composition and sensory characteristics of wines was investigated. Must and wine had a large quantity of mono-terpenes, mainly linalool, geraniol, and nerol. The most abundant glycosylated fraction was the mono and poly-oxygenated terpenes, followed by benzene compounds and norisoprenoids. Must skin contact at 18 °C during 15 and 23 h produced an important increase in the free and bound varietal compounds, which suggests the use of glycosidic enzymes, together with skin maceration, to increase wine aroma. From a sensory standpoint, must skin contact was very positive, since it brought about an increase in the fresh and fruity characteristic of the wines, and they also had more body.     

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.     

Aroma release of a model wine solution as influenced by the presence of non-volatile components. Effect of commercial tannin extracts, polysaccharides and artificial saliva

The effect of commercial tannin extracts, extracted either from grape seeds or grape skins, a natural wine polysaccharide extract, pectin and arabinogalactan on the headspace release of selected aroma compounds from a “model wine” solution was investigated. Changes in the volatility of the aroma compounds were studied using headspace solid-phase microextraction combined with GC/FID. The performance of four commercially available fibre coatings was checked and the 50/30 ??m DVB/CAR/PDMS one was proved to be the most effective. A short sampling time (1 min) was used to determine the “true” headspace concentration at equilibrium between the headspace and the sample. In general, the volatility of the studied aroma compounds appeared to be correlated to increasing tannin levels as well as to their origin. The volatility of esters was generally increased upon tannin addition at low concentrations, while at higher addition levels the two extracts exhibited dissimilar behaviour attributed to their different composition. Both arabinogalactan and pectin addition at low concentrations increased the volatility of the studied aroma compounds, while at higher concentrations pectin exhibited a different behaviour by salting out hydrophobic compounds in the vapour phase. In addition, grape skin and seed tannin extracts in admixture with polysaccharides either prevented the macromolecular chains to associate with volatile molecules or led to additional flavour retention depending on the aroma compound and the addition level. Saliva addition enhanced the volatility of the most hydrophobic compounds whereas the hydrophilic compounds were retained into the matrix.     

Bound aroma compounds of Gual and Listán blanco grape varieties and their influence in the elaborated wines

Listán blanco and Gual are two white grape varieties grown in Spain (Canary Islands) and Gual is also grown in Portugal (Madeira Island). Wine quality could be improved by exploiting the varietal characteristics present in grapes as aroma precursors. At the present time, the enologic potential of these varieties has not yet been studied. Aroma precursors in musts and skins, and free volatiles in wines were determined in samples of both varieties. Aroma precursors of must and skins were isolated by absorption on XAD-2 resin and the aglycone liberated by means of acid hydrolysis. Free volatiles from wines and from aroma precursors were extracted with dichloromethane and then analysed by gas chromatography-mass spectrometry (GC–MS). Among the aroma precursors analysed, only α-terpineol, linalool and linalool oxides, 4-allyl-2,6-dimethoxyphenol, 2-methoxy-4-vinylphenol, 4-hydroxybenzaldehyde, vanillin and benzyl alcohol showed contents in grapes comparable to the levels observed in wine volatile compounds.     

Impact of cover crops in vineyard on the aroma compounds of Vitis vinifera L. cv Cabernet Sauvignon wine

This study compared the influence of different cover crops with clean tillage on wine aroma compounds of 5-year-old Cabernet Sauvignon vines. White clover, alfalfa, and tall fescue were used in the vineyard and compared with clean tillage. Aroma compounds of wine were analysed by solid-phase microextraction gas chromatography–mass spectrometry (SPME-GC/MS). Forty-seven volatile compounds were identified and quantified. Wines made from grapes grown with various cover crops had higher levels of aroma compounds. Ethyl acetate, isoamyl acetate, ethyl octanoate, ethyl hexanoate, phenylethyl acetate, isoamyl alcohol, linalool, citronellol, β-damascenone, α-ionone, and 5-amyl-dihydro-2(3H)-furan were the impact odorants of sample wines. Wines from cover crop also had higher contents of these impact odorants than the control. For different cover crops, alfalfa sward yielded the highest levels, followed by the tall fescue treatment. According to the data analysis of aroma compounds and sensory assess, permanent cover crop may have the potential to improve wine quality.     

Evaluation of the influence of mastication on temporal aroma release of ripe and unripe bananas,using a model mouth system and gas chromatography-olfactometry

The effect of the mastication rate on temporal aroma release from ripe and unripe bananas was investigated using a model mouth system and analysing the volatiles by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry. Large differences were found in the numbers of odour active compounds of ripe and unripe bananas as well as for the three different mastication rates investigated (0, 26 and 52 min^-1). Hexanal was the only compound that was detected by all six assessors for ripe and unripe bananas for each mastication speed. In the odour profile of ripe and unripe bananas with a mastication rate of 52 min^-1, 18 and 7 significant odour active compounds respectively were detected whereas with a mastication rate of 26 min^-1, 15 and 3 respectively were detected. Without mastication only 3 and 2 compounds respectively were observed. Principal component analysis on GC-O data allowed an easy separation between the three chewing speeds and the ripe and unripe bananas.     

Study of volatile organic acids in freeze-dried Cheonggukjang formed during fermentation using SPME and stable-isotope dilution assay (SIDA)

Volatile organic acids in freeze-dried Cheonggukjang were quantified using a stable-isotope dilution assay (SIDA) according to the fermentation period. Five organic acids, acetic acid, propanoic acid, 2-methylpropanoic acid, butanoic acid, and 3-methylbutanoic acid, were identified using solid-phase microextraction (SPME) in conjunction with gas chromatography–mass spectrometry (GC–MS). The contents of volatile organic acids in Cheonggukjang were highly dependent on the fermentation period and they increased during fermentation. Moreover, the branched-chained organic acids (namely 2-methylpropanoic acid and 3-methylbutanoic acid) were formed earlier and were present at much higher contents than the corresponding straight-chained organic acids during Cheonggukjang fermentation.     

The use of oak chips during the ageing of a red wine in stainless steel tanks or used barrels: effect of the contact time and size of the oak chips on aroma compounds

Background and Aims:  This paper reports the influence of adding oak chips to a wine being aged either in stainless steel tanks or in used barrels on aroma compounds, comparing these wines with those aged in new barrels. Both the size of the oak chips and the length of contact time were considered.
Methods and Results:  Aroma compounds were analysed by gas chromatography–mass spectrometry to determine the differences in these compounds between the samples. The results showed that chips release aroma compounds into wine very rapidly, an effect that was clearly seen when they were added to the wines stored in tanks. The wines aged in new barrels continued to extract aroma compounds for a longer time, and higher concentrations were reached in these wines for most aroma compounds. Wines in used barrels with added oak chips behaved in an intermediate manner.
Conclusions:  Although overall quality is better in wines matured in new barrels, the use of oak chips could be considered a good choice for producing short-aged wines and for reusing used barrels under good sanitary conditions.
Significance of the Study:  The rapid spread of technique alternatives to oak ageing justifies studies to assess the influence of oak chips on the chemical characteristics of wines and to evaluate any differences from traditional oak ageing systems.     

Influence of oil degradation on the amounts of acrylamide generated in a model system and in French fries

Acrylamide formation in foodstuffs is subjected to different influencing factors. This study investigates the specific impact of both oil oxidation and oil hydrolysis on the formation of this probable human carcinogen. This was achieved using two heating methodologies. The first one was based on a closed stainless steel tubular reactor, in which different homogenized potato powder mixtures were heated. Doing so, possible changes in the altered heat transfer properties of the oil upon degradation are excluded since direct contact between the food and the heat medium is eliminated. The results obtained from these experiments were compared with standardized French fry preparation trials. Using both heating methodologies, acrylamide formation was proven to be independent upon oil oxidation and hydrolysis status in the experimental conditions used. More specifically, no evidence from the experimental results could be found that, due to oxidative or hydrolytic oil degradation, heat transfer properties of the oil were changed in such an extent that acrylamide formation during French fry preparation would be significantly influenced. Finally, it could be concluded that the investigated oil degradation products, such as glycerol, mono-, and diacylglycerols, did not significantly influence the acrylamide formation.