Medium-chain Fatty Acid Ethyl Esters Research Articles

Esters and higher alcohols regulation to enhance wine fruity aroma based on oxidation-reduction potential

Fruity aroma is a crucial element in reflecting the flavor of wine, believed to be closely linked to esters and higher alcohols associated with the oxidation-reduction potential (ORP) of wine. In this work, the impact of ORP on the production of esters and higher alcohols, and consequently the fruity aroma in Cabernet Sauvignon (CS) and Ecolly wines were investigated. Results revealed that the maximum concentration of medium-chain fatty acid ethyl esters (MCFAEEs) was achieved at −80 mV, which was 48.78% and 25.10% higher than those of the CK groups (ORP without artificial control) in CS and Ecolly wines, respectively. However, the concentrations of acetates and higher alcohols in CS were not significantly different from that in CK, while those in Ecolly were elevated. Additionally, the temperate fruity aroma in CS and citrus aroma in Ecolly wines were enhanced at −80 mV. Partial least-squares regression further indicated that, higher alcohols contributed positively to these enhanced aromas of CS and Ecolly. MCFAEEs have also been suggested to have a positive impact on the fruity and floral aromas for CS and tropical fruity aroma for Ecolly wines. Our work provides an alternative for improving the aroma quality of wine through fermentation process.

Partial dealcoholization of a Malbec wine through pervaporation with a PDMS membrane: Effect of operation temperature on process economics, volatile aroma composition and sensory properties

In the present work, partial dealcoholization of a Malbec red wine with 14.8% v/v alcohol by pervaporation through a PDMS membrane (polydimethylsiloxane) was addressed. The influence of the process temperature on the economy of the process, the composition of volatile aroma compounds and wine sensory characteristics was deeply analyzed.To do so, partial dealcoholization experiments at lab scale were run with the pervaporation setup operated at a permeate pressure of 0.013 bar and at three different temperatures; i.e. 35, 40 and 45 °C. Two types of runs were carried out: (i) simple runs to build a conceptual model of the process and (ii) repetitions to accumulate an adequate volume of partially dealcoholized wine (10.5%v/v) to allow the sensory analysis of the following Malbec wines: the initial wine, the partially dealcoholized wines and the blends in a 70/30 ratio (13.5% v/v)).From the conceptual modeling stage the required value of the fractional pervaporation advance ηreq of 0.09 was obtained, as well as the average values of permeate overall fluxes at 35, 40 and 45 °C; i.e., 1.02, 1.38 and 1.82 kg m−2 h−1, respectively. For all variants, a permeate product with an alcohol content of 54% v/v was estimated. Experimental values agreed reasonably well with those obtained from the model simulation.The conceptual modeling of the process enabled the scaling-up of the process and the subsequent economic analysis. The best figures corresponded to the design with heat integration at 45 °C when earnings estimated from the sale of the ethanol-rich permeate to the local market was taken into account.Fresh Malbec, partially dealcoholized wines at the selected temperatures, and their corresponding blends were chemical and sensory characterized. Dealcoholized wines showed differences concerning the operating temperature on the volatile and total acidity, fructose, anthocyanins, tannins, total polymers, and CIELAB parameters, except lightness. The total and volatile acidity were affected by the temperature and showed an increase in dealcoholized and blended wines with the respective decrease of the pH. Dealcoholization favored the presence of large polymeric pigments (0.6 in initial wines and an average of 0.96 in blends), which are associated positively with color stability.Volatiles were also affected by the operating temperature, decreasing the concentration of all chemical groups in these wines. A total of thirty-two free volatile organic compounds (VOCs) including higher alcohols (HA), medium chain fatty acid ethyl esters (MCFAEE), higher alcohol acetates (HAA), medium chain fatty acids (MCFA), norisoprenoids (NI) and terpenoids (TP) were identified and quantified.Finally, sensory evaluation demonstrated that partially dealcoholized wines could not be differentiated by the operation temperature. The fullness, astringency, pungency, floral notes, bitterness, color intensity, and sweetness were significant variables that allowed differentiate between initial, partially dealcoholized, and blend wines. Despite the loss of volatile compounds, blended wines showed higher intensity of floral attributes, and in mouth were lesser astringent, bitter, and pungent than the fresh wine.From an overall perspective, pervaporation of fresh wine with a PDMS membrane at 45 °C and the adoption of a dilution ratio of 70/30 for initial wine to partially dealcoholized wine result in a promising strategy to reduce the alcohol content without affecting the sensory quality of the final red wine.

Controlled Aeration Driven by Oxidation-Reduction Potential Affects Ester Profile in Wine Alcohol Fermentation with Different Starter Cultures

Background and Aims. Aeration, an important operation in winemaking, cannot be controlled accurately based on dissolved oxygen for ester production in wine alcohol fermentation. The following study describes an aeration control method with oxidation-reduction potential (ORP) in alcohol fermentation and investigates its effect on ester production in fermentations with different starter cultures. Methods and Results. The proposed method is based on using ORP as a switch for aeration timing. Different aeration levels driven by ORP were performed in wine alcohol fermentation with different starter cultures including Saccharomyces cerevisiae (Sc), Pichia fermentans (Pf), Hanseniaspora uvarum (Hu), and their mixes (Pf/Sc and Hu/Sc). The accumulated aeration volume, residual sugar concentration, viable cell number, and ester concentration were analyzed. Results showed that aeration levels could be controlled effectively with an ORP value, and aeration with higher ORPs triggered faster sugar utilization in Sc and Hu/Sc fermentation. Pf and Hu survived one day less in their respective cofermentation with aeration when ORP was −100 mV or −50 mV compared to the natural ORP (−150 mV∼−105 mV in Pf/Sc and −141 mV∼−107 mV in Hu/Sc, respectively). Aeration driven by ORP changed ester profiles in cofermentations. With the aeration levels increasing, the proportion of medium-chain fatty acid ethyl esters in the concentration of total esters first increased and then decreased in Hu/Sc fermentation. When ORP was −100 mV in Pf/Sc fermentation, the proportion of higher alcohol acetates to total esters was highest (8.14%), while that of ethyl acetate to total esters was lowest (87.35%). Conclusions. Aeration driven by ORP improved wine ester profiles by increasing the proportion of medium-chain fatty acid ethyl esters or reducing that of ethyl acetate in cofermentations. Significance of the Study. The present study will allow wineries and researchers to optimize the aeration process in alcohol fermentation and develop a scientific aeration strategy to improve the wine ester profile and aroma quality.

Fruit Wine Obtained from Melon by-Products: Physico-Chemical and Sensory Analysis, and Characterization of Key Aromas by GC-MS.

About 20% of fresh fruits and vegetables are rejected for not meeting the superficial aesthetic standards (color, shape, and size). Part of the food production is not used in the human food chain. The transformation of these fresh products into novel re-valuable ones is a challenge for a sustainable food industry. This research studies an alcoholic fermentation fruit-based wine from two melon (Cucumis melo L.) cultivars: Jimbee® (smooth and yellow skin with orange flesh) and Okashi® (netted yellow-orange skin with pale green flesh). The melon juice (must) was fermented by Saccharomyces cerevisiae and enriched in sucrose and organic acids to achieve alcoholic fermentation, acidity, and flavors, obtaining a fruity-flavored and dry melon-based wine with 10° alcoholic grade, in both melon cultivars. The volatile compounds were measured by GC-MS and the odor activity value (OAV) was calculated. The Jimbee and Okashi melon wines increased their aromatic profile due to an increment in medium-chain fatty acid ethyl esters such as ethyl hexanoate, ethyl octanoate, and ethyl decanoate (OAV > 1), which contributed to the fruity aroma. Other volatile compounds such as ethyl 9-decenoate and phenethyl acetate (OAV > 1) appeared in the Okashi wine, which brought a floral aroma. For sensory evaluation (40-100), the Jimbee cultivar, with its orange flesh, scored 68.2 and the Okashi cultivar, with pale green flesh, scored 82.8, which was the preferred melon-based wine. This is an example of a circular economy model to produce a fruit-based wine with commercial potential and satisfactory sensory evaluation.

Effect of inorganic and organic nitrogen supplementation on volatile components and aroma profile of cider

To investigate the impact of inorganic and organic nitrogen on volatile compounds of cider, various levels (60, 150 and 240 mg N/L) of diammonium hydrogen phosphate (DAP) and amino acids mixture were added to apple juice before fermentation, respectively. The qualitative and quantitative of volatile substances were carried out by GC–MS. Further, sensory and electronic nose analysis was performed to analyze the aroma profile of cider. Both DAP and amino acids mixture promoted fermentation, significantly affected volatile compositions and increased perceived aromas of cider. Adding 60 mg N/L DAP significantly increased volatile compounds content, especially medium-chain fatty acid ethyl esters (MCFAEEs) and fatty acids (FAs), whereas higher alcohols and acetate esters concentrations were remarkably increased with 150 mg N/L amino acids supplementation. Partial least-squares (PLS) regression analysis suggested that MCFAEEs contributed the most to tropical fruity aroma. The study provides a theoretical foundation for high-quality cider brewing.

Oxidation-reduction potential affects medium-chain fatty acid ethyl ester production during wine alcohol fermentation

The medium-chain fatty acid ethyl esters (MCFAEEs) are a group of important aroma compounds generated during wine production. Wine alcohol fermentation involves several redox processes, which are affected by the oxidation–reduction potential (ORP). However, the mechanism via which ORP regulates MCFAEE production remains unclear. To investigate the effect of ORP on MCFAEE production, wine alcohol fermentation was performed using Saccharomyces cerevisiae under different ORPs. The results demonstrated that the ORPs studied (except for 90 mV) did not significantly affect cell growth, sugar consumption, and ethanol production, while the MCFAEE concentration in the simulated wines can be manipulated by ORP operation. MCFAEE levels increased till 96 h, and then decreased. The maximum MCFAEE level of 1222.97 μg/L was obtained after 96 h at 0 mV, which was 45.32% higher than that of the control. During the increase, higher relative expression of ACC1, FAS1, FAA2 and EEB1, elevated external citric acid flux, and moderate intracellular NADP+/NADPH ratio were observed at 0 mV compared to that at other ORPs. During the decrease, lowest relative expression of POX1 was detected at 0 mV. We showed for the first time the relationship between ORP operation and MCFAEE production in winemaking, which will improve the aroma quality of wine.

Characterization of an Aspergillus niger for Efficient Fatty Acid Ethyl Ester Synthesis in Aqueous Phase and the Molecular Mechanism.

Fatty acid ethyl esters are important flavor chemicals in strong-flavor baijiu. Microorganisms are the main contributors to ester synthesis during baijiu manufacture. However, the ester synthesis was unstable between batches. This was owing to a limited knowledge of the mechanisms for ester synthesis by microorganisms. In this work, a fatty acid ethyl ester synthesizing Aspergillus niger strain CGMCC (China General Microbiological Culture Collection) 3.4309 was identified. The conversion ratios of ethyl valerate, ethyl caproate, ethyl caprylate, and ethyl caprate were 7.87, 29.20, 94.80, and 85.20%, respectively, under the optimized conditions. A comparison of transcriptomes under the initial and optimized ester synthetic conditions indicated that 23 genes were upregulated in transcription level and encoded enzymes with potential abilities for ester synthesis. Eleven of the enzymes were expressed, and three of them, numbered An605, An1097, and An3131, showed the ability to catalyze fatty acid ethyl ester synthesis under aqueous phase, with capric acid as the preferred substrate. The possible enzymatic catalytic mechanism was proposed based on homology modeling and molecular docking. This study reported for the first time that A. niger showed the ability to efficiently catalyze the synthesis of short- and medium-chain fatty acid ethyl esters in aqueous phase, identified the key enzymes, and analyzed the basic enzymatic properties. This is helpful to promote the application of related microorganisms and enzyme resources in the baijiu industry.

Performance of a novel β-glucosidase BGL0224 for aroma enhancement of Cabernet Sauvignon wines

β-glucosidase is widely used in food industry for its glycosidic hydrolysis properties. In this paper, performance of a novel β-glucosidase BGL0224 from Oenococcus oeni for aroma enhancement of Cabernet Sauvignon wines was explored for the first time. The main projects included electronic nose, gas chromatography-mass spectrometry and sensory analysis. Principal component analysis indicated that electronic nose had the ability to discriminate different treatments by responding specifically to volatile compounds. Adding BGL0224 before alcoholic fermentation significantly increased the “aromatic index” of Cabernet Sauvignon wines. Compared with the control group, adding BGL0224 increased more than 15 volatile aroma compounds of Cabernet Sauvignon wines. Furthermore, with the addition of BGL0224 before alcoholic fermentation, the concentrations of medium-chain fatty acid ethyl esters, long-chain fatty acid ethyl esters and terpenes in wines were 3004.19 ± 36.14 μg/L, 4090.37 ± 94.07 μg/L and 210.21 ± 8.98 μg/L respectively, which were all significantly higher than other treatments. Sensory analysis showed that BGL0224 increased “tropical fruity”, “sweet fruity” and “floral notes” characteristics while inhibited “citrus” characteristics of Cabernet Sauvignon wines. Overall, this study provided support for industrial application of BGL0224 by evaluating its performance for aroma enhancement of Cabernet Sauvignon wines.

Increase of medium-chain fatty acid ethyl ester content in mixed H. uvarum/S. cerevisiae fermentation leads to wine fruity aroma enhancement

Medium-chain fatty acid (MCFA) ethyl esters, as yeast secondary metabolites, significantly contribute to the fruity aroma of foods and beverages. To improve the MCFA ethyl ester content of wine, mixed fermentations with Hanseniaspora uvarum Yun268 and Saccharomyces cerevisiae were performed. Final volatiles were analyzed by gas solid phase microextraction-chromatography-mass spectrometry, and aroma characteristics were quantitated by sensory analysis. Results showed that mixed fermentation increased MCFA ethyl ester content by 37% in Cabernet Gernischt wine compared to that obtained by pure fermentation. Partial least-squares regression analysis further revealed that the improved MCFA ethyl esters specifically enhanced the temperate fruity aroma of wine. The enhancement of MCFA ethyl esters was attributed to the increased contents of MCFAs that could be induced by the presence of H. uvarum Yun268 in mixed fermentation. Meanwhile, the timing of yeast inoculations significantly affected the involving biomass of each strain and the dynamics of ethanol accumulation.

Use of Lysozyme and Oligomeric Proanthocyanidin to Reduce Sulfur Dioxide and the Evolution of Volatile Compounds in Italian Riesling Ice Wine During Aging Process

In order to reduce sulfur dioxide (SO2) level in ice wine making, the effects of low SO2, lysozyme and oligomeric proanthocyanidin (OPC) on the volatile compounds were, respectively, studied during 1 year aging process. Based on the previous study, seven treatments of Italian Riesling ice wine were carried out for monitoring the evolution of volatile compounds. Results of gas chromatography mass spectrometry (GC-MS) showed that, about 180 mg/L SO2 not only increased total alcohols content in Italian Riesling ice wine, but also significantly correlated with certain higher alcohols during 1 year aging process. Meanwhile, the final concentration of medium-chain fatty acid ethyl esters and the corresponding fatty acids were found highly related to lysozyme adding. Moreover, OPC played a positive role in stabilizing the total content of esters at a level around 200 mg/L, it mainly due to its excellent ability of free oxygen scavenging. Finally, principal components analysis (PCA) was conducted to reclassify major volatile compounds and 14 typical volatile components were defined. Practical Application This article was technically supported by our previous research: Development of lysozyme-combined antibacterial system to reduce sulfur dioxide and to stabilize Italian Riesling ice wine during aging process and mainly studied three volatile compounds evolution (alcohols, acids and esters) in Italian Riesling ice wine during 1 year aging process. It not only illustrated SO2 can not be totally replaced after alcohol fermentation because of its extraordinary contribution on alcohols and esters composition, but also indicated an appropriate range of SO2 addition (180–200 mg/L) contributes to the synthesis of fruity and floral bouquet for aging. On the other hand, the addition of lysozyme and OPC not only improved the activity of LAB inhibition and antioxidant for ice wine aging, but also promoted certain esters evolution, which contributed more complexities for ice wine bouquet. It further proved the utilization of our system can be very promising and beneficial for reducing SO2 concentration and stabilizing Italian Riesling ice wine during aging process.

Solvent-Free Lipase-Catalyzed Synthesis of Diacylgycerols as Low-Calorie Food Ingredients.

Problems derived from obesity and overweight have recently promoted the development of fat substitutes and other low-calorie foods. On the one hand, fats with short- and medium-chain fatty acids are a source of quick energy, easily hydrolyzable and hardly stored as fat. Furthermore, 1,3-diacylglycerols are not hydrolyzed to 2-monoacylglycerols in the gastrointestinal tract, reducing the formation of chylomicron and lowers the serum level of triacylglycerols by decreasing its resynthesis in the enterocyte. In this work, these two effects were combined to synthesize short- and medium-chain 1,3-diacylglycerols, leading to a product with great potential as for their low-calorie properties. Lipase-catalyzed transesterification reactions were performed between short- and medium-chain fatty acid ethyl esters and glycerol. Different variables were investigated, such as the type of biocatalyst, the molar ratio FAEE:glycerol, the adsorption of glycerol on silica gel, or the addition of lecithin. Best reaction conditions were evaluated considering the percentage of 1,3-DAG produced and the reaction rate. Except Novozym 435 (Candida antarctica), other lipases required the adsorption of glycerol on silica gel to form acylglycerols. Lipases that gave the best results with adsorption were Novozym 435 and Lipozyme RM IM (Rhizomucor miehei) with 52 and 60.7% DAG at 32 h, respectively. Because of its specificity for sn-1 and sn-3 positions, lipases leading to a higher proportion of 1,3-DAG vs. 1,2-DAG were Lipozyme RM IM (39.8 and 20.9%, respectively) and Lipase PLG (Alcaligenes sp.) (35.9 and 19.3%, respectively). By adding 1% (w/w) of lecithin to the reaction with Novozym 435 and raw glycerol, the reaction rate was considerably increased from 41.7 to 52.8% DAG at 24 h.

Interactions between Dissolved β-Glucans and Medium-Chain Fatty Acid Ethyl Esters in Model Beer Solution and Their Impact on Filterability

As shown in previous studies, not only the concentration of the dissolved beer ingredients but also their molecular size could influence their filterability. Therefore, polysaccharides of malt, especially β-glucan, are reported to have the greatest impact on filtration behavior. In the present study, the effects of barley (1,3;1,4)- and yeast (1,3;1,6)-β-glucan combined with aroma-relevant substances of beer were studied in Kieselguhr and membrane filtration (polyethersulfone, 0.45 æm) using ethanolic (4% w/w) model solutions. An increasing β-glucan concentration was found to have a negative impact on both applied filter types. The concentration increase of barley β-glucan to 300 mg/L decreased the filtrate flux more than 40% during membrane filtration. In contrast, pure medium-chain fatty acid (MCFA) ethyl esters had no effect on filterability. Mixed with (1,3;1,4)-β-glucan, the filtrate flux decreased from 400 kg/(h × m2) to less than 250 kg/(h × m2). A decrease of MCFA ethyl ester up to 90% was measured in the filtrate. Compared with barley β-glucan, an equivalent concentration of yeast β-glucan caused a flux decrease of more than 95% during membrane filtration. In summary, synergistic effects on filterability with polysaccharides and fermentation byproducts could be shown.

The yeast enzyme Eht1 is an octanoyl-CoA:ethanol acyltransferase that also functions as a thioesterase.

Fatty acid ethyl esters are secondary metabolites that are produced during microbial fermentation, in fruiting plants and in higher organisms during ethanol stress. In particular, volatile medium-chain fatty acid ethyl esters are important flavour compounds that impart desirable fruit aromas to fermented beverages, including beer and wine. The biochemical synthesis of medium-chain fatty acid ethyl esters is poorly understood but likely involves acyl-CoA:ethanol O-acyltransferases. Here, we characterize the enzyme ethanol hexanoyl transferase 1 (Eht1) from the brewer's yeast Saccharomyces cerevisiae. Full-length Eht1 was successfully overexpressed from a recombinant yeast plasmid and purified at the milligram scale after detergent solubilization of sedimenting membranes. Recombinant Eht1 was functional as an acyltransferase and, unexpectedly, was optimally active toward octanoyl-CoA, with kcat = 0.28 ± 0.02/s and KM = 1.9 ± 0.6 μm. Eht1 was also revealed to be active as a thioesterase but was not able to hydrolyse p-nitrophenyl acyl esters, in contrast to the findings of a previous study. Low-resolution structural data and site-directed mutagenesis provide experimental support for a predicted α/β-hydrolase domain featuring a Ser–Asp–His catalytic triad. The S. cerevisiae gene YBR177C/EHT1 should thus be reannotated as coding for an octanoyl-CoA:ethanol acyltransferase that can also function as a thioesterase. © 2014 The Authors. Yeast published by John Wiley & Sons, Ltd.

Reversal of the β-oxidation cycle in Saccharomyces cerevisiae for production of fuels and chemicals.

Functionally reversing the β-oxidation cycle represents an efficient and versatile strategy for synthesis of a wide variety of fuels and chemicals. However, due to the compartmentalization of cellular metabolisms, reversing the β-oxidation cycle in eukaryotic systems remains elusive. Here, we report the first successful reversal of the β-oxidation cycle in Saccharomyces cerevisiae, an important cell factory for large-scale production of fuels and chemicals. After extensive gene cloning and enzyme activity assays, a reversed β-oxidation pathway was functionally constructed in the yeast cytosol, which led to the synthesis of n-butanol, medium-chain fatty acids (MCFAs), and medium-chain fatty acid ethyl esters (MCFAEEs). The resultant recombinant strain provides a new broadly applicable platform for synthesis of fuels and chemicals in S. cerevisiae.

Supercritical fluid fractionation of fatty acid ethyl esters from butteroil

Countercurrent supercritical fractionation of the fatty acid ethyl esters from butteroil has been investigated. The main objective of the present study was to obtain extracts rich in short- and medium-chain fatty acid ethyl esters. To that end, transesterification of the original butteroil was used to transform the triacylglycerols into the corresponding fatty acid ethyl esters. Then, several supercritical fluid extractions were carried out at pressures ranging from 8.9 to 18.6MPa and at 2 different temperatures (48 and 60°C). The flow ratio of CO2 to butteroil was 15. Composition and yield of short- and medium-chain fatty acid ethyl esters was evaluated at different extraction conditions. Extracts containing ∼70% short- and medium-chain fatty acid ethyl esters were obtained at 101 bar and 60°C, and can be used as starting material for the production of highly valuable functional lipids.

The Saccharomyces cerevisiae EHT1 and EEB1 Genes Encode Novel Enzymes with Medium-chain Fatty Acid Ethyl Ester Synthesis and Hydrolysis Capacity

Fatty acid ethyl esters are secondary metabolites produced by Saccharomyces cerevisiae and many other fungi. Their natural physiological role is not known but in fermentations of alcoholic beverages and other food products they play a key role as flavor compounds. Information about the metabolic pathways and enzymology of fatty acid ethyl ester biosynthesis, however, is very limited. In this work, we have investigated the role of a three-member S. cerevisiae gene family with moderately divergent sequences (YBR177c/EHT1, YPL095c/EEB1, and YMR210w). We demonstrate that two family members encode an acyl-coenzymeA:ethanol O-acyltransferase, an enzyme required for the synthesis of medium-chain fatty acid ethyl esters. Deletion of either one or both of these genes resulted in severely reduced medium-chain fatty acid ethyl ester production. Purified glutathione S-transferase-tagged Eht1 and Eeb1 proteins both exhibited acyl-coenzymeA:ethanol O-acyltransferase activity in vitro, as well as esterase activity. Overexpression of Eht1 and Eeb1 did not enhance medium-chain fatty acid ethyl ester content, which is probably due to the bifunctional synthesis and hydrolysis activity. Molecular modeling of Eht1 and Eeb1 revealed the presence of a alpha/beta-hydrolase fold, which is generally present in the substrate-binding site of esterase enzymes. Hence, our results identify Eht1 and Eeb1 as novel acyl-coenzymeA:ethanol O-acyltransferases/esterases, whereas the third family member, Ymr210w, does not seem to play an important role in medium-chain fatty acid ethyl ester formation.

Effect of antioxidant protection of must on volatile compounds and aroma shelf life of Falanghina (Vitis vinifera L.) wine.

Two vinification methods involving different degrees of antioxidant protection of Falanghina must during prefermentative steps, and referred as HAMP (high antioxidant must protection) and LAMP (low antioxidant must protection), were compared in terms of fermentation performances of four different yeast strains, composition of the volatile fraction of wines at the end of alcoholic fermentation, and shelf life of wines during storage. The use of HAMP technology resulted in wines with lower volatile acidity and higher concentrations of medium-chain fatty acid ethyl esters, acetates, and volatile fatty acids. For two of the four strains a lower concentration of isoamyl alcohol was also observed. HAMP wines also revealed increased shelf life because of the higher concentration of odor active esters at the end of storage and better preservation of varietal aromas.