Acceleration of ripening and improvement of quality of olive pickles by encapsulated cells in nano/micro-tubular cellulose

Abstract

An industrial process for black table olives fermentation was followed in order to study the effect of immobilized halophile culture and the initial halophile culture concentration in combination with temperature for a period of 30 days. For comparison, three types of batch fermentation were investigated: (a) fermentation with the indigenous microbiota (control), (b) inoculated fermentation with isolated mixed halophile culture (MHC) and (c) inoculated fermentation with isolated MHC on tubular cellulose (TC). The effects of (i) temperature (5 and 20 °C) and (ii) initial biomass concentration (0.15, 0.5, 1 and 1.5 g/300 ml brine) on pH, brine and total volatiles were studied. Immobilized MHC cells on TC increased the fermentation rate as compared with free MHC cells. When immobilized MHC was used in fermentation, pH values remained close to 4.0 for all initial culture concentrations and lower than that for natural fermentation for 30 days at 5 °C. Especially for 1 g of biomass/300 ml of brine initial culture, the pH remained lower than 3.4 during the 30 days of fermentation at 5 °C. At the case of immobilized halophile cells at 5 °C, propionic acid was produced (max. 26.74 ± 1.21 g/L) which acted as natural preservative, while there was increase in total volatiles.