Manufacture of food ingredients with biological activity for human gut health from lemon peels: a comparative evaluation of several processing routes

• Lemon peels can be used as a source of products with several biological activities. • Liquors enriched in oligogalacturonides and polyphenols were obtained by hydrothermal treatment and further processed. • The biological properties depends on the downstream processing route. • A product showed high selectivity against the RKO colon cancer line and high antioxidant activity and could have interest as food ingredient for gut health. Lemon peels were subjected to hydrothermal treatment and the liquors obtained were processed following several downstream processing schemes obtaining a variety of products with different composition. Up to five products were generated, analysed for their saccharide and polyphenolic content and tested for their antimicrobial, antioxidant and anticancer (cytotoxicity) activities. Unfortunately, none of the products showed antimicrobial activity under the assayed conditions. However, the raw hydrothermal treatment product (P1) and the P4 variant (P1 after enzymatic tailoring) exhibited the highest antioxidant activity for ABTS and FRAP tests (6.12 and 0.98 for P1, and 7.98 and 0.96 g Trolox/100g non-volatile content for P4, respectively). Regarding anticancer activity, P1 exhibited a high selectivity index (1.99) against the RKO colon cancer cell line, with reduced effect on the BJ-5ta fibroblast cell line (control). The IC 50 for P1 on RKO was 14.4 mg/mL, The IC50 value for P1 on RKO was 14.4 mg/mL, which is in line with the required prebiotic doses for POS. These activities and the expected prebiotic potential make this product a promising functional food ingredient for improve gut health.