Pilot-scale application of selected microbial starters to enhance the nutritional and sensorial traits of fermented and pasteurized table olives

Table olives represent a fundamental food source in the Mediterranean diet owing to their nutritional and bioactive properties. After determining the optimal conditions for fermenting black table olives at the laboratoryscale, in this study, starter-driven and spontaneous fermentations of the Leccino cultivar were studied in an industrial facility. A single inoculum of lactic acid bacteria, LAB1 (Leuconostoc mesenteroides), LAB2 (Lactiplantibacillus plantarum), of yeast, YST1 (Debaryomyces hansenii) and YST2 (Saccharomyces cerevisiae) strains, and a coinoculum LAB1 + YST2 (Leuconostoc mesenteroides + Saccharomyces cerevisiae) were used as starters to conduct the fermentation process and to counteract the development of pathogens and undesired microorganisms. Chemical and biochemical parameters confirmed the good outcome of the process and the improvement of nutritional traits, especially in the case of the LAB1 and LAB1 + YST2 treatments. These two strategies enhanced the total phenolic content by approximately 1.3-1.6 and 2.0-2.4 times and the corresponding antioxidant activity increased by about 1.2-1.4 and 1.8-2 times, in comparison with spontaneous fermentation and the raw material, respectively. Moreover, the same treatments resulted in the most appreciated sensory attributes and low levels of defects and off-flavors in the final products. The VOCs analysis highlighted the prevalence of esters in the LAB1 + YST2 sample. After in vitro digestion, the total bio-accessibility of phenolic compounds was quite high, with percentages ranging between 57.22 % and 74.03 %, in olives fermented by the mixed starter culture LAB1 + YST2 and those fermented by the LAB1 strain, respectively. These outcomes were useful to validate table olive starter-driven fermentation strategies on a pilot-scale and inside an industrial environment.