Production of bioactive protein-enriched hydrolysates from fish by-products using autohydrolysis

Protein demand is expected to double by 2050 [1]. The amount of by-products generated from the fish processing industry represents more than half of the entire fish weight. These materials are commonly discarded with high costs and environmental burden [1,2]. Giving their high protein content (57%, dry weight), fish- based by- and co-products could be used in the development and fortification of food and feed products, thus contributing to bioeconomy and sustainability. Hydrolysis has been widely used to extract protein from several matrixes and the resulting hydrolysates usually exhibit interesting bioactive and functional properties [3,4]. The present work aimed the production of bioactive protein-enriched hydrolysates from fish by-products, using water under subcritical conditions. For that, the raw material was homogenized and centrifugated at 8000 g and 4 ºC for 30 min. The resulting solid biomass was used for the hydrolysis experiments. Several temperatures (150 to 230 ºC) and times (5 to 30 min) were tested, using 20 g (dry weight) of biomass and 0.4 L of water. After the hydrolysis, the solubilization yields were determined and the hydrolysates were analysed for their chemical composition, peptide profiles (HPLC) and antioxidant activity (in vitro colorimetric assays). The solubilization yields increased with temperature and time of reaction. All hydrolysates presented antioxidant activity, being the best conditions at temperatures between 170 and 230 C. Moreover, all hydrolysates presented high protein content (up to 82%). Autohydrolysis proved to be an efficient method for the solubilization and hydrolysis of protein from fish by-products without the need for chemicals or expensive enzymes. Antioxidant hydrolysates with high protein content were produced, which could be useful in the development of and fortification of food and feed products and could be a possible path to a rational and integral use of scarce protein sources in the near future.
The authors would like to thank Sebol - Comércio e Indústria de Sebo S.A. for providing the fish by-products. This work was financially supported by Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2020 unit Further support was obtained by Portugal 2020, European Structural and Investment Funds (ESIF) and Agência Nacional de Inovação, S.A. (ANI) under the scope of the project HeathyPETFOOD- PetFood formulations for promotion of health and quality of life (POCI-01-0247-FEDER-047073).
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