A sequential multi‐strain inoculation approach for designing functional Sicilian table olives

The exploitation of microbial strains with advanced technological traits is a pivotal step in enhancing the production of table olives and meeting consumers' demands. Here, a multi-step approach involving the sequential addition of a Lactiplantibacillus plantarum (namely C11C8) starter strain and a Lacticaseibacillus rhamnosus (namely VB1) probiotic strain with confirmed bile salt hydrolase activity was applied for the production of Nocellara Etnea and Tonda Iblea cultivars, fermented at 7% NaCl. Results revealed that in olives inoculated with the starter, staphylococci and Enterobacteriaceae were found below detectable limits. Furthermore, fermentation significantly increased total phenolic content (TPC) and radical scavenging activity (RSA) in Tonda Iblea brine samples, with the highest values for TPC (310.13 μg gallic acid equivalent mL-1) and RSA (222.27 μmol Trolox equivalent mL-1) after 150 and 120 days, respectively. Furthermore, the presence of the probiotic strain, confirmed by quantitative PCR, resulted in a slight reduction of TPC, although a value of 219.63 μmol Trolox equivalent mL-1 in Nocellara Etnea brine samples was detected after 150 days. The volatile organic compound profiles revealed that in samples inoculated with the two strains, benzaldehyde and α-farnesene, associated with fruity and floral notes, were detected. In contrast, the control samples exhibited higher levels of guaiacol and 4-ethylphenol, known for imparting off-flavors. Sensory analysis confirmed that consumers preferred olives enriched with the probiotic, for their aromatic complexity and reduced off-flavors. The proposed approach results in a promising strategy for designing lower-sodium functional table olives.