Ethyl decanoateCharpentier, in Managing Wine Quality: Oenology and Wine Quality The characteristic ethyl decanoate smell of cava is acquired mainly during decaonate ageing process when yeast autolysis and physico-chemical changes occur. There may be two explanations for this formation and decrease of esters. Yeasts contain enzymes simultaneously involved in the formation and degradation of esters.
Charpentier, in Managing Wine Quality: Oenology and Wine Quality , The characteristic aroma of cava is acquired mainly during the ageing process when yeast autolysis and physico-chemical changes occur. There may be two explanations for this formation and decrease of esters. Yeasts contain enzymes simultaneously involved in the formation and degradation of esters. Alternatively, some esters, especially long-chain esters, could be adsorbed on the cell walls Pozo-Bayon et al.
Vitispiranes could originate from the hydrolysis of glycosidically-bound precursors, which are carotenoid-derived megastigmane compounds. TDN may be a direct degradation product of carotene, although two possible glycosylated precursors have been reported in grape juice Silva Ferreira and Guedes de Pinho, This slow release or nucleic acid degradation is due to the unfavourable conditions for the autolysis process of champagne making.
However, the formation of flavour nucleotides during this process was not studied. These compounds have little or no flavour or aroma themselves but can enhance the flavour and mouthfeel of other compounds.
Ribonucleotides were only detected in yeast autolysate in a study on Champagnes Zhao and Fleet, , The threshold values of the most representative nucleotides in Champagne wines were higher than the concentrations found in the same wines.
However, it is known that there is synergism between the different nucleotides and also in the presence of glutamic acid. The concentrations of phenethyl acetate, ethyl octanoate, and ethyl decanoate increased by a factor of 2.
Noticeably, isoamyl acetate, ethyl hexanoate, and ethyl dodecanoate were detected only in OP-containing medium at concentrations of 0. Considering that dissolved oxygen negatively regulates the formation of volatile esters  , in the second series of experiments, the effect of OP on the production of the above compounds was evaluated with the influence of a limited oxygen supply under semi-anaerobic conditions. As is shown in Figure More specifically, depending on the volatile ester, a 4- to fold increase in yield was observed with regard to the respective values in the absence of OP.
Sponholz, in Managing Wine Quality: Volatile esters are important compounds of the wine aroma. As a result, changes in ester composition with ageing have often been reported to affect the aroma composition of wines Simpson, ; Marais and Pool, ; Chisholm et al. The variation in their concentrations during ageing is different; esters may increase or decrease during storage due to chemical esterification or hydrolysis towards chemical equilibria Simpson, ; Ramey and Ough, ; Zoecklein et al.
The initially-produced esters are slowly hydrolyzed during storage until an equilibrium is reached with the corresponding acids and alcohols Chisholm et al. In particular, during wine ageing, a decrease can be found in the concentrations of isoamyl acetate, hexyl acetate, 2-phenylethyl acetate, ethyl butyrate, ethyl caprate, ethyl caprylate, ethyl caproate, ethyl 4-hydroxybutyrate, ethyl hexanoate and hexyl hexanoate Simpson, ; Marais and Pool, ; Zoecklein et al.
Ethyl esters hydrolyze more slowly than acetate esters, so the apple aroma of ethyl butyrate and ethyl 2-methylbutyrate will not be lost very quickly Ramey and Ough, ; Chisholm et al. On the other hand, an increase during storage is found for ethyl acetate, diethyl succinate, ethyl lactate, ethyl monosuccinate and diethyl malate Marais and Pool, ; Rapp et al.
Opposite tendencies, however, may also occur, so that ethyl esters of caproic, caprylic and capric acids can also increase during ageing Marais and Pool, Besides the earlier mentioned compounds, large number of aroma and fragrant compounds that provide organoleptic characteristics of various wine types are also detected Ferreira, For example, the main constituents of cherry flavors include methanol, ethanol, butanol, pentanol, octanol, geraniol, linalool, ethyl acetate, acetic acid, isovaleric acid, octanoic acid, and benzaldehyde Dharmadhikari, In pomegranate juices, volatile compounds can be grouped in four main chemical families: After fermentation, in pomegranate wine following fragrance compounds prevail: Aldehydes and ketones are produced in smaller amounts during incomplete alcoholic fermentation or oxidation of alcohol, but still very important for the generation of varietal aromas.
Nevertheless, in higher concentrations they have undesirable effects, thus being considered as off-odor. In fruit wines, aldehydes have been detected in comparable amounts: In pomegranate wines, detailed analysis of volatiles showed presence of decanal, nonanal, and octanal in range from 0. Esters are also present in fruit and berry wines as one of the major ingredients defining final wine taste.
They are responsible for the fruity bouquet of wines, where mixtures of esters may not possess the same intensity or qualitative attributes as individually van der Merwe and van Wyk, In cashew, mango and apple wines total amount of esters were 82—, 15—35, and In blackberry wines, major esters are ethyl caprylate, diethyl succinate, and ethyl caproate, with overall values ranging from Fourteen of the 38 sensory attributes differed significantly across treatments Table CS All wet chemistry attributes differed significantly among the wines as did all Harbertson-Adams parameters Table CS The pH of the screw closure wines was lower than the pH for the cork synthetic and natural closure wines.
Additionally, all volatile compounds except hexanol, 2-phenyl ethyl alcohol, acetic acid, isovaleric acid, and octanoic acid differed significantly across treatments Table CS The same was true for the ethyl octanoate concentration in cork closed wines, whether synthetic or not, but in the case of the screw-capped wines the concentration of ethyl octanoate did not change significantly with temperature.
It is clear that wines with little or no oxygen ingress screw or wines stored at lower temperatures had higher auc values than wines with higher oxygen ingress naco This means that less of the present oxygen was consumed during oxidative reactions.
The natural cork closed wines did not differ from either the synthetic cork closed or the screw cap wines. However, it is very difficult to interpret this figure, therefore we replotted the same information with only the top 15 contributing variables Fig. Variable contributions to a dimension component have a value between 0 and 1 and all variables associated with a component sum to 1. Thus, variables with high contribution on a dimension are more important to that dimension than one with lower contributions Abdi et al.
Lastly, we also asked the MFA program to list the variables that were significantly linked to each dimension Table CS Based on all the aforementioned we can say that TPO is associated with wines that had been stored at lower temperatures and thus less oxygen in the bottles was consumed. Wine stored at higher temperatures had lower sulfur dioxide values, lower total tannins and anthocyanins content as well as less phenethyl acetate.
Screw cap closed bottles had higher concentrations of ethyl decanoate , ethyl octanoate, and ethyl hexanoate than bottles closed with synthetic corks. The bottles with synthetic corks had higher pH and more HS oxygen. Numerous attempts have been made to associate certain metabolites with microbial spoilage Nychas and Panagou, The microbial volatile organic compounds MVOCs are generated in this process as well, and the amount of MVOCs can reflect the condition of microbial growth and food spoilage directly Wang et al.
In a recent review, Wang et al. VH12, and Trichoderma sp. VS20 inoculated in strawberry jam. Unfortunately, correlating the production of molecules responsible for or associated with spoilage appearance to the functions of spoilage microorganisms is not always possible. There are several reasons for this limitation; spoilage may result from a large variety of processes. It can be the consequence of a complex succession of enzymatic reactions, potentially associated with nonenzymatic reactions, such as meat discoloration, or with enzymatic reactions originating from both the spoilage organisms and the food matrix like lytic activities of enzymes from muscle cells.
Another example is metabiosis that results from enzymatic reactions successively carried out by different microorganisms Remenant et al. Spoilage can also result from reactions catalyzed by enzymes that are not well identified. Finally, some molecules responsible for spoilage can be produced by many different enzymes and identifying those that produce them in food may be a challenge Remenant et al.
Liu, in Brewing Microbiology , Esters of short-chain and branched-chain fatty acids, which are most aroma-active, are arguably the most important volatile compounds in beer. They have a positive impact on the overall beer flavour, especially aroma, but excessive levels of esters can lead to overly fruity, fermented off-flavour.
Esters found in beer can be categorised into two main groups: In general, esters impart fruity flavour notes with sensory descriptions ranging from fruity and solvent-like ethyl acetate , banana- and pear-like isoamyl acetate , rose- and honey-like 2-phenylethyl acetate , or apple-like and sweet ethyl hexanoate and ethyl octanoate. Esters can be synthesised chemically or biologically in beer.
Brewing yeasts are undoubtedly the principal ester producers in beer fermentation. Esters and their formation mechanisms in brewing S. Therefore, it is beyond the scope of this section to elaborate the details of ester biosynthesis, and interested readers are referred to these review articles for further information.
However, a summary of ester biosynthesis based on these reviews are provided below. Ester formation is associated with yeast growth in the early phase of fermentation.
Acetate esters are produced via the reaction between an alcohol and acetyl Co-A, which is catalysed by the enzyme alcohol acetyl transferases ATF1 and ATF2.
Ethanol, branched-chain alcohols and 2-phenylethanol are the common moieties of acetate esters. Ethyl esters of medium-chain fatty acids are formed through the reaction between ethanol and respective fatty acyl Co-A, which is catalysed by the enzyme alcohol acyl transferases.
Saccharomyces cerevisiae strains also produce esterases that hydrolyse esters, and thus the final concentration of esters in beers is the net balance between ester synthesis and hydrolysis.
Strains of brewing yeasts produce predominantly ethyl esters of fatty acids, particularly ethyl octanoate, with relatively little formation of acetate esters. In the absence of oxygen, grape cells switch from respiratory to fermentative metabolism. This shift is more rapid if air is immediately flushed out with carbon dioxide. Because carbon dioxide is more dense than air, it displaces air around the fruit.
It is readily dissolved by cytoplasm, where it induces ion leakage Yurgalevitch and Janes, It also shifts the equilibria of cellular decarboxylation reactions Isenberg, In addition, carbon dioxide may accelerate the breakdown of pectins, by inducing the synthesis of grape pectinases.
Biochemically, grape-cell alcoholic fermentation is similar to that found in yeasts and most other cells. The primary end product is ethanol, with smaller accumulations of glycerol, acetaldehyde, acetic acid, and succinic acid. This results from the early inactivation of alcohol dehydrogenase in grape cells. However, ethanol accumulation is, by itself, insufficient to fully explain enzyme inactivation Molina et al.
Instead, enzyme activity probably ceases as an indirect result of ethanol-induced membrane disruption and cell death Romieu et al. The resultant release of organic acids, stored in cell, would inhibit alcohol dehydrogenase activity by lowering cytoplasmic pH.
During grape-cell fermentation, malic acid is metabolized to other acids primarily oxaloacetic, pyruvic, and succinic acids , as well as ethanol. Depending on the grape variety, and fermentation temperature Flanzy et al. Significant decarboxylation to lactic acid does not occur. The other major grape acids tartaric and citric are occasionally metabolized.