Bi-objective optimization of tuna protein hydrolysis to produce aquaculture feed ingredients

Abstract

Fish meal is commonly employed as protein source in aquaculture diets. The enrichment of this ingredient with fish protein hydrolysates (FPH) and free amino acids has proved to improve larval development and feed assimilation. In this work, we produced tuna head hydrolysates using a sequential enzymatic treatment employing Alcalase and Flavourzyme. Statistical modelization coupled with bi-objective optimization were employed to optimize the operating parameters (i.e. pH, temperature and duration of the Flavourzyme treatment) for producing a FPH with a desired molecular weight profile. More specifically, this work focused on the content of small peptides between 700–2500 Da (F 2500 ) and that of free amino acids (F 250 ), supported by their benefits as aquaculture feed ingredients. The optimal reaction conditions for maximimizing the release of free amino acids F 250 (i.e, pH 7.2, 43–49 °C, Flavourzyme treatment above 160 min) were detrimental for the content of F 2500 . A bi-objective optimization approach was then proposed, able to find a set of intermediary solutions (Pareto Front) presenting maximal F 2500 for a range of free amino acids level between 2–30%. This allows the selection of the operating parameters for producing a FPH with a desired weight profile, based on the specific needs of the farmed species.