Abstract
The aim of this work was the recovery of protein substrates from monkfish waste (heads and viscera) generated in the on-board processing of this species. Initially, the effect of pH, temperature, and protease concentration was studied on mixtures of a 1:1 ratio (w/v) of monkfish heads/water. The optimal conditions of proteolytic digestion were established at 57.4 °C, pH 8.31, [Alcalase] = 0.05% (v/w) for 3 h of hydrolysis. Later on, a set of hydrolysis at 5L-pH-stat reactor were run under the aforementioned conditions, confirming the validity of the optimization studies for the head and viscera of monkfish. Regarding the chemical properties of the fish protein hydrolysates (FPH), the yield of digestion was higher than 90% in both cases and the degrees of hydrolysis and the soluble protein content were not especially large (<20% and <45 g/L, respectively). In vitro digestibility was higher than 90% and the percentage of essential amino acids ranged from 40 to 42%. Antioxidant activities were higher in viscera FPH, and antihypertensive ability was superior in head FPH. The values of number average molecular weights (Mn) of monkfish hydrolysates were 600 Da in the viscera and 947 Da in the head. The peptide size distribution, obtained by size-exclusion chromatography, indicated that the largest presence of peptides below 1000 Da and 200 Da was observed in the viscera FPH.
Highlights
An increasing global population, the effects of climate change, and the loss of productive croplands driven by urbanization, among other factors, pose substantial challenges for food and nutrition security in the following decades, especially for poorer countries [1,2]
Monkfish head is a tasteful substrate for the preparation of fish fumet, its on-board processing routinely leads to the sea dumping of this material in many fisheries
The valorization of monkfish wastes by means of a hydrolysis treatment may be executed in order to recover this protein source, which should be demanded of the fishing industry to comply with the objectives of the circular bioeconomy
Summary
The effects of climate change, and the loss of productive croplands driven by urbanization, among other factors, pose substantial challenges for food and nutrition security in the following decades, especially for poorer countries [1,2]. Many fisheries are currently overexploited, and fish production must become sustainable in order to satisfy demand in the long run [3]. Among the range of measures proposed for sustainable fish production, valorization of by-catch and processing by-products allows for an increase in resource efficiency and minimization of waste [4,5]. This strategy has demonstrated the possibility of isolating valuable compounds from specific tissues. From a more general perspective, most fish waste contains a significant amount of proteinaceus material, and in consequence, processes to recover this fraction present wider applicability
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