Invasive silver carp (Hypophthalmichthys molitrix) protein hydrolysates- A potential source of natural antioxidant.

摘要

Invasive silver carp (Hypophthalmichthys molitrix), continue to spread over the Mississippi River causing a great concern for the river ecosystem due to their impact on native fish species. To minimize the negative effects of silver carp, many strategies were implemented including using it for animal feed, as fertilizers or simply discarding them into waste. However, these fish are high in protein content, making them excellent starting material for protein-derived by-products. One alternative is to recover and modify the protein in the fish into bioactive food ingredient. In the functional/ nutraceutical food industry, there is high demand for antioxidant agents. In this study, silver carp hydrolysates (SPH) were evaluated for their antioxidant activity using in vitro assays which simulate food and in vivo cell model. This study also attempts to understand the factors affecting antioxidant activity of SPH.;The general goals of this study were to (1) evaluate the antioxidant potential of SPH prepared using two different commercial enzymes (Flavourzyme RTM and AlkalaseRTM) and to characterize the amino acid composition of the SPH in order to understand the influence of free amino acid composition on different antioxidant mechanisms; (2) to evaluate antioxidant activity of SPH using a Caco-2 cell based model and to determine the relationship between molecular weight of the peptide fractions and antioxidant activity (3) to determine the effect of simulated gastro intestinal digestion of SPH on its cell based antioxidant activity.;The results showed that most of the SPH samples displayed higher or comparable antioxidant capacity than commercial antioxidants (BHA, BHT and &agr; tocopherol). Further, the antioxidant activity of the SPH was shown to depend on the presence of specific amino acids which include acidic amino acids and hydrophobic amino acids. In addition, peptide fractions with low molecular weight (<3 KDa) improved cell based antioxidant activity even after longer incubation time under both oxidative stress and non-stress conditions. Dose dependent cell based antioxidant activity was observed in the low molecular weight peptide fractions. Lower molecular weight peptide fraction of FlavourzymeRTM SPH showed higher activity than AlcalaseRTM SPH due to presence of high number of peptides with active sequence in former than later. In addition, simulated gastrointestinal digestion of Flavourzyme RTM SPH using a lower digestion enzyme activity was able to retain its activity and also was able to show dose dependent activity. Overall, SPH displayed potential antioxidant capacity both in chemical based and cell based assays thus providing alternatives for using an invasive fish in the form of potential functional, bioactive ingredients.