BioScience Blog – Научный Биологический блог

One of the most popular ways of table olives preparing in the south of Portugal (Algarve) is the crushing them before the fermentation step. After harvesting and sorting olives are broken, washed, brined in salt solutions, and fermented at room temperature during traditional process which remains craft and empirical. The aims of this work were the characterization of traditional fermentation process of Manzanilla variety of Olea europaea fruits concerning the

microbiological and physicochemical evolution. The microbiological parameters studied were yeasts, lactic acid bacteria and Enterobacteriaceae. The physicochemical parameters measured were pH, total acidity and reducing sugars. Another task of this work was isolation of yeasts and identification them by Restriction Fragment Length Polymorphism (RFLP) method. Olives were fermented at room temperature with wild microbiota during 29 days in the laboratory of Microbiology of University of Algarve, Faro, Portugal. Yeasts were the main microorganisms responsible for the fermentation of the olives. The lactic acid bacteria were absent. The level of Enterobacteriaceae increased during the first two days with the following decrease probably due to the combined inhibitory effect of pH and brine concentration. From the 12th day of the fermentation until the end Enterobacteriaceae group of bacteria was not found. At the first day of fermentation pH values were 5.01 (fermentation A) and 5.02 (fermentation B). The pH values decreased slightly until reaching values of 4.43 for fermentation A and 4.25 for fermentation B on the day 29. Concentration of sugars increased in the first 2 days, probably due to the diffusing of sugars from the olives to the brine, and then decreased till the end of fermentation due to their consumption by the microorganisms during the fermentation process. 60 strains of yeasts were isolated throughout the fermentation, and were joined by morphological similarities into 14 strains. These 14 strains belong to 3 species which were identified by RFLP using PCR products. One group of isolates was not found in the database and additional experiments for characterization of them are ongoing. The rest of the isolates belong to the species Rhodotorula glutinis and Candida vinaria. This work was supported by Erasmus Mundus External Window Cooperation Lote-8 grant.