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21The volatile profiles of Spanish-style green table olives elaborated with Manzanilla, 22Gordal and Hojiblanca cultivars grown at different locations in Spain were established 23 by solid phase micro-extraction (SPME) and gas chromatography coupled to mass 24 spectrometry (GC-MS). A total of 102 volatile compounds were identified, belonging to 25 distinct chemical classes, and 20 of them are reported for the first time in table olives. 26The headspace profile was predominated by alcohols and phenols, followed by acids 27 and esters, whereas the relative amounts of the remaining classes were quite lower (< 28 5% in general). The principal compounds characterizing the headspace for most samples

The aim of the present study was to assess the malodorous spoilages of Spanish-style green table olives through microbial and metabolite composition using current measuring techniques (e.g., high-throughput DNA sequencing, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry). Under different alkaline and washing conditions, the spoilage fermentations were reproduced with Gordal and Manzanilla olive cultivars using a low salt concentration (71 g L−1 NaCl) in the initial brine. The degradation of lactic acid and significant increases in volatile fatty acids and phenols were found in all the spoiled samples in comparison with the unspoiled control samples. According to high-throughput DNA sequencing, Cardiobacteriaceae and Ruminococcus were the dominant bacteria in the spoiled samples. PLS regression and Pearson’s correlation coefficient analyses revealed positive and negative correlations among microbial communities, metabolites, and sensory spoilage descriptors. Notably, the “zapatera” descriptor was significantly associated with Propionibacterium, which was positively correlated with acetic acid, propionic acid, succinic acid, and methyl propanoate; while the “butyric” descriptor exhibited a significant positive relationship with the genus Ruminococcus, which gave an almost significant correlation with propionic and butyric acids.

Changes in physicochemical characteristics, substrate depletion, and product formation during fermentation were followed in both brine and olive juice in order to achieve a complete knowledge of fermentation chemistry in Spanish-type green olives. Both spontaneous and controlled fermentations were investigated. Fermentation rate, irrespective of the type of fermentation, was lower in olive juice than in brine, but the main acid products eventually reached equilibrium. Final free acidity remained significantly (p < 0.05) higher, and combined acidity remained lower, in brine than in olive juice in both fermentations, but differences in final pH were not significant in controlled fermentation. Final concentrations of lactic and formic acids were significantly (p < 0. 05) higher, and those of ethanol and succinic acid were lower, in controlled fermentation than in spontaneous fermentation. Butanediol, attributable to Enterobacteriaceae growth, was formed only in the latter case. Calculated carbon recoveries were not significantly (p < 0.05) different in any case, giving a mean of some 78%.