# Volatile Composition of Industrially Fermented Table Olives from Greece
## 3 Results and Discussion
### Volatile Composition of Table Olives
On the contrary, 2-butanol was more abundant than ethanol in CNS samples grown in FTH and EVIA. A similar pattern was observed within the HLK table olives grown in different locations (KAV, HAL). The content of phenylethyl alcohol was higher in HLK and CNS samples (\(\sim\)2.0-4.0%) than KLM ones (\(\sim\)0.5%) and varied significantly between the growing location of each cultivar. Similar findings were observed for 1-hexanol and (\(Z\))-3-hexenol. The above-mentioned results reflect different activity of yeasts and lactic acid bacteria between the cultivars as well as the growing locations of olives. It is generally known that ethanol is an end-product of the Embden-Meyerhof-Parnas glycolytic pathway, whose main function is the production of energy [13]. The biosynthesis of higher alcohols is linked to the catabolism of amino acids and sugars [37]. As suggested by [PERSON] et al. [7,12], C5-C6 alcohols, aldehydes and their corresponding esters, such as 1-hexanol, 3-hexen-1-ol, hexanal and hexyl acetate, can be produced either from polyunsaturated fatty acids through the endogenous lipoxygenases or/and a similar pathway mediated by the microbial enzymes in brine. Esters were the most numerous chemical class of volatile compounds detected in our study. Acetate and propanoate esters were quantitatively the most important. More specifically, the dominant esters in KLM samples were mainly ethyl acetate and ethyl propanoate, followed by propyl acetate, methyl acetate, 3-methylbutyl acetate and ethyl lactate (Table 2). The latter three compounds were significantly different between the two growing locations (AIT, PEL) of the KLM cultivar. On the contrary, the principal esters of CNS samples were ethyl propanoate and propyl acetate (representing \(\sim\)20% of total volatiles), of which the latter was present at significantly lower levels (\(p<0.05\)) in the samples from the MAG location. The same pattern was observed for propyl propanoate, which was also found in appreciable levels only in the samples from FTH and EVIA locations. It is worth to mention that several butanoate esters, such as ethyl butanoate, were detected in higher levels in MAG samples as compared to FTH and EVIA olives. This could be explained by the high content of butanoic acid in MAG olives, as mentioned before. As regards the olives of the HLK cultivar (processed with the Spanish method), the profile of esters was remarkably different between the samples grown in HAL and KAV. The most notable differences can be focused on the higher content of acetate esters, such as ethyl acetate, propyl acetate and 3-methylbutyl acetate, as well as ethyl lactate, found in HAL olives. On the other hand, the content of the major propanoate esters (methyl and propyl propanoate; ethyl propanoate excluded) was significantly higher in KAV samples. This is probably related with the corresponding higher level of propanoic acid in the latter samples, as previously mentioned. Esters are well known to contribute significantly to the flavor of both natural and fermented foods and are appreciated since they generally carry fruity flavors [38]. Acetate esters and propanoate esters could be synthesized by alcohol acyltransferase (AAT), which catalyzes the esterification of volatile alcohols with acetyl CoA and propionyl CoA, respectively, to produce volatile esters and free CoA-SH [13]. The most obvious factors that influence ester synthesis are the availability of substrates and the level of enzyme activities. Other parameters, such as pH, temperature and NaCl content, can also influence the production of esters [38]. From the six volatile phenols identified, special emphasis should be given to guaiacol and 4-methylguaiacol. They accounted for \(\sim\)12% of total volatiles in HLK samples, whereas significantly lower amounts (\(p<0.05\)) were observed in the CNS and KLM samples. In addition, guaiacol was found in appreciable levels only in the KAV samples as compared to HAL olives.