Effect of brine replacement and salt concentration on the fermentation of naturally black olives

Abstract

This study was undertaken to modify the traditional fermentation of naturally black olives in order to obtain higher quality black table olives. After holding olives in tap water or low salt brine prior to fermentation, acidification of the cover brine and fermentation at two different salt concentrations (6 and 14 g/ 100 ml NaCl) were applied to Gemlik variety olives in three batches. Fermentations were monitored using physical, chemical and microbiological analyses and effects of the above changes to fermentation were investigated. Yeasts were the predominant microorganisms in all of the batches. Growth enhancement of lactic acid bacteria by brine replacement occurred in the fermentation with 6 g/ 100 ml NaCl cover brine but not with 14 g/100 ml NaCl brine. The highest level of titratable acidity (0.59 g/100 ml) formed during fermentation with 6 g/100 ml NaCl brine followed by fermentation with 6 g/100 ml NaCl brine (0.43 g/100 ml) where the brine was replaced after 48 days. The lowest level of titratable acidity (0.36 g/100 ml) was formed using a high salt brine. Reducing sugars were consumed effectively by microorganisms in all the batches and residual levels in the brines were 0.05–0.1 g/100 g ml. NaCl contents of the final products were 5.20 g/ 100 g (olives with high salt brine) and 3.27–3.58 g/100 g (olives with low salt brine). Moisture contents of the processed olives were in the range 49.58–50.79 g/ 100 g. The water activity ( a w) value of olives fermented with the high salt brine was found to be 0.947 while a w values of olives fermented with the low salt brine were 0.962–0.964. Protein content of the olives ranged between 1.76–1.95 g/100 g and the ash contents were found to be 2.41–2.81 g/100 g in olives with low salt brine and 4.70 g/100 g in olives with high salt brine. According to sensory evaluations of the final products, no differences between the treatments were found ( P > 0.05).