Almond skin spontaneous fermentation promotes the selection of lactic acid bacteria starters with exopolysaccharide-producing activities to be used as by-product industry applications

Almond skin, a by-product of almond processing, is rich in polyphenols—plant-derived compounds with significant potential benefits for human health. However, it is primarily used in animal feeding or fuel production. The first aim was selection of starter cultures to be used in innovative food set-up, based on the addition of fermented almond skin as ingredient. The methodology involved spontaneous fermentation of almond skin, based on Type I sourdough daily propagation technology, to obtain a LAB-dominated ecosystem. LAB strains were isolated, and evaluated for their exopolysaccharide-producing activity, exploitable due to both their impact on human health and their technological properties. A selected pool of LAB strains was employed in a 24-hour fermentation of almond skin, to assess its efficacy at industrial by-product chain level. Results demonstrated that almond skin fermentation led and supports the establishment of a robust LAB ecosystem featured by an increase in antioxidant and prebiotic compounds. In evaluating resilience to almond skin niche, we identified 12 LAB strains and selected two of them (Leuconostoc mesenteroides UNLB14 and Lactiplantibacillus plantarum UNLB7), as the ones harbouring a stronger acidification power. At the same, these LAB enhanced the nutritional profile and contributed to the bioactive potential of the fermented almond skin. Furthermore, these strains showed an important rheological power supported by metabolomics profiles that highlighted metabolites conferring almond and floral notes. This research underscores the viability of almond skin as a functional ingredient, prompting its sustainable reuse and its future employment in innovative food production.