Recovery of antioxidant protein hydrolysates from shellfish waste streams using subcritical water extraction

Abstract

In recent years, a growing number of studies have demonstrated that protein hydrolysates have interesting functional properties and a strong antioxidant capacity, amongst other important bioactivities. In this work, the potential of subcritical water (ScW) to efficiently extract bioactive protein hydrolysates contained in brown crab shell residues was evaluated. Aiming at maximizing the extraction of the target molecules, the impact of operating temperature (150, 200, and 250 °C), solid/liquid ratio (1:5, 1:10, and 1:15 g/mL), and heating rate (3 and 6 °C/min) on ScW extraction performance was assessed. Extracts were then evaluated in terms of total protein content, Maillard reaction products formation, free amino acid profile, and antioxidant potential through oxygen radical absorbance capacity assay. Results have shown that, although an increase in operating temperature allowed a significant increase in global extraction yields, there was a slight decrease (approximately 1.4-fold) in the extraction selectivity towards proteins. Nevertheless, higher temperatures enabled the production of extracts with a higher antioxidant potential, possibly due to an increase of smaller peptides/free amino acids and Maillard reaction products. Therefore, the study reported herein reinforces that ScW represents a viable sustainable alternative extraction media for the recovery of protein hydrolysates from shellfish biomass, with potential to be used as ingredients in industrial applications.