Valorisation of saffron floral by-products through fermentation: a focus on the antimicrobial activity

Saffron is obtained from the stigmas of Crocus sativus L. flowers, and after their removal, the remaining 80 % of the flower, including stamens and tepals, are discarded. Therefore, this work aimed to investigate the fermentability of saffron by-products and their valorisation through the recovery of antimicrobial extracts. To evaluate the fermentability of saffron by-products, a Design of Experiment was applied and the growth ability of 20 microbial strains, mainly lactic acid bacteria and one yeast, was tested. The best-adapted strains (Limosi-lactobacillus fermentum, Lacticaseibacillus rhamnosus, Lacticaseibacillus paracasei and Pediococcus acidilactici) were selected, and the antimicrobial activity of extracts from the fermented matrices was evaluated against Salmonella enterica, Listeria monocytogenes, Staphylococcus aureus and Escherichia coli. After the extraction process, especially the extracts obtained from the fermented matrices showed antimicrobial activity (Minimum Inhibitory Concentration values ranged between 50 and 25 mg/mL). To test the reproducibility of the fermentation and the antimicrobial activity of fermented matrices, by-products from different Mediterranean countries, collected in different years and subjected to different post-harvest treatments, were evaluated. The growth ability observed in the different matrices was comparable and in line with the predicted model as the antimicrobial activity.