Microbiological monitoring of olive fermentation process of Gemlik type dry-salted black olives and investigation of the effect of pasteurization on the product’s shelf life

Abstract

In the present research, the microbiological changes that occurred during the fermentation process of traditionally produced Gemlik style dry-salted olives, locally known as “sele”, were monitored. Following the fermentation process, microbiological, chemical and organoleptic changes were investigated for the products which were stored at room temperature for a period of 6 months after various pasteurization processes (non-brined, oiled and non-oiled). At the initial stages of fermentation, microbial flora consisted of molds and lactic acid bacteria, and in the following stages no presence of lactic acid bacteria could be detected. None of Gemlik style dry-salted (sele) olive samples contained coliform bacteria. During the storage period, the highest total bacteria count (1,2x105 cfu/g) was detected in the control-oiled group and the lowest total count (10 cfu/g) was observed in the pasteurized non-oiled group. The samples within the control group exhibited mold growth, whereas the pasteurized samples rarely exhibited yeast/mold growth. Throughout the storage period, dry matter, pH, total acidity, protein, oil content and oleuropein (absorbance) values of samples were monitored, and no significant change was observed among the sample groups. In general, all samples were relished according to the organoleptic evaluation results conducted after fermentation and throughout the storage period. However, with their attractive appearance, oiled group Gemlik style dry-salted (sele) olives were preferred at higher rates compared to non-oiled samples with dull appearance. Additionally, the slightly rancid taste of oiled group samples towards the end of the storage period, received adverse opinions of some of the panelists. Saltiness values, on the other hand, were found to be at normal levels.