Vapor Analysis of Fermented Spanish‐type Green Olives by Gas Chromatography

Abstract

SUMMARY: Five major components were detected gas chromatographically in the head‐space vapor (HSV) of Spanish‐type green olives fermented by pure cultures of Lactobacillus plantarum, Pediococcus cerevisiae and Leuconostoc mesenteroides. Three of these compounds were identified as acetaldehyde, methyl sulfide, and ethanol. The same compounds were present in unfermented olives but in different amounts. Olives that had undergone a natural fermentation contained the above five compounds, and, in addition, a varying number of other compounds. These results indicated that HSV analysis may be a rapid method for detecting volatile end products resulting from the metabolism of various microorganisms. A high ethanol content was found in olive brines that contained a predominance of yeasts. Abnormal fermentations gave unique HSV profiles, one of which indicated a high level of 2‐butanol. Methyl sulfide was found to be a major odor component of fermented as well as unfermented olives. Acetaldehyde and ethanol contributed secondarily to the odor. Primary contributions of fermentation by the above lactic acid bacteria to the flavor of olives were: (1) production of a desirable level of acidity, and (2) utilization of fermentable sugars to the exclusion of microorganisms which produce metabolic end products with undesirable flavor characteristics.