In recent years, the consumption of fish products has led to a worrying trend where approximately two-thirds of the total amount of fish is discarded as waste. At the same time, scientific interest in exploring natural collagen sources has increased. This study explores the potential of valorizing sardine scales (Sardina pilchardus), a by-product of the canning industry, through the extraction of collagen for potential use in cosmetic formulations and food supplements.

Collagen from sardine scales was obtained through acid and enzymatic extraction. The extracts were characterized by UV-Vis, FTIR, SDS-PAGE, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The collagen was hydrolyzed with papain to small peptides. Subsequently, the biological activities of acid-soluble collagen and the collagen peptides in terms of antioxidant and antimicrobial activity were evaluated. Furthermore, the capacity of collagen peptides to permeate the intestinal barrier, simulated with caco-2 cells, was evaluated. Purified collagen extracts were obtained, with the enzymatic extraction method yielding three times higher than the acid method. The SDS-PAGE analysis confirmed the extraction of type I collagen as well as its hydrolysis into small fragments (25-12 kDa). While no antimicrobial activity was observed, collagen peptides exhibited three times more antioxidant capacity than non-hydrolyzed collagen. Meanwhile, in 6 hours, about 6.37 % of collagen peptides could permeate the intestinal barrier.

This work represents a continuous effort to advance our understanding and valorization of marine co-products, focusing on collagen extraction for the development of food supplements, thus contributing to the sustainable evolution of the circular blue economy.