Innovative analytical protocol to pre-select lactic acid bacteria able to control table olive production

To evaluate the technological aptitude of new strains of lactic acid bacteria to ferment table olives, a lot of trials of olive fermentation are usually carried out using the new isolates. Aim of the present study was to develop an innovative analytical protocol - easy, cheap, and fast - to pre-select lactic acid bacteria high-tolerant to phenolic compounds and increasing the antioxidant activity and, consequently, the shelf-life of the table olives. The protocol was tested on 183 strains of autochthonous lactic acid bacteria. The strains were isolated from artisanal Calabrian table olives and brines at different stages of fermentation. The olives were of the following cultivars: Carolea, Geracese, Nocellara messinese, Ottobratica, Roggianella, and Sinopolese. The pH indicator 5',5"-dibromo-o-cresolsulfophthalein (bromocresol purple) was added to MRS agar to prepare a screening substrate where the strain biomass assumed colors significantly different, based on the amount of lactic acid produced. Using this and other phenotypical parameters the 183 strains were reduced to 83 excluding the worst and their duplicates. The remaining 83 lactic acid bacteria were inoculated in thermized olive paste with the addition of sodium chloride and water. The fermentation was monitored determining every week pH and titratable acidity. After 28 days the total lactic acid (D+L) was determined by OxiTester K270 plus (by CDR, Firenze, Italy). This way, only the best 15 strains will be more completely tested in the final selection. So the proposed analytical protocol allows excluding strains unable to act as starter in easy, cheap, and fast way.