Changes in chemical and microbiological composition of two varieties of olive during fermentation

Abstract

In this study, the changes in chemical and microbiological composition of two olive varieties, Edincik and Gemlik, have been examined during fermentation at industrial scale. Prior to processing, the olives have been thoroughly characterized chemically and microbiologically. Then, the nature of the fermentation process has been investigated during the 9 months of fermentation period by taking samples at certain intervals. The most important characteristics of the two varieties before processing were determined as follows: Edincik variety was found to have relatively higher reducing sugar (5.94%) and moisture (59.53%) contents than that of Gemlik variety (4.45% reducing sugar and 43.18% moisture). Polyphenol concentrations of two varieties were 2.50% and 2.40%, respectively. During fermentation, reducing sugar and polyphenols contents were decreased gradually in the fruit, while other constituents were slightly changed or remained almost unchanged. While reducing sugar decreased to the values of 0.98% and 0.65%, free acidity in brine increased to 0.41% and 0.35%, pH value of brine were 4.4 and 4.9 and salt content in fruit were reached to the final values of 7.4% and 6.9% for Edincik and Gemlik varieties, respectively. Microflora of the raw samples was consisted of various bacteria mainly, lactobacilli, Gram-negative, anaerobic sulfide producing, coliform bacteria and yeasts. During the fermentation of both varieties, yeasts were dominated starting from the 40th days of fermentation.