Enzymatic production of antioxidative and antimicrobial hydrolysates from cod solid side-streams

In the last decade, there has been an increased focus and interest in increasing the utilization of existing raw materials and reducing waste especially due to the increasing global population. In the cod filleting industry, up to 60% (w/w) of the biomass end up as side-streams for example, frame, head and gut, which are either used as low value products such as animal feed or are wasted. An example of animal feed is mink feed. However, in Denmark, the mink production is closed due to COVID-19 and new utilization possibilities are needed. The cod side-stream used in this study is from Royal Greenland and is very fresh with the possibility of freezing right after production to maintain quality and increase shelf life before further production. Cod frames still contain meat after filleting and could be used as hydrolysates with bioactive properties such as antioxidative and/or antimicrobial activity for food or feed applications. Previous studies have shown that longer peptides (shorter hydrolysis time) potentially have antimicrobial properties and shorter peptides (longer hydrolysis time) have antioxidative properties. Therefore, an experiment was designed using three different types of proteases (Alcalase, Neutrase and Protamex) and different hydrolysis time (½, 1, 2, 3 and 6 h) to produce different hydrolysates. Produced hydrolysates were evaluated for their antioxidative and antimicrobial activities by in vitro antioxidant assay, radical scavenging (DPPH), and metal chelating activity, and by disc diffusion and minimal inhibitory concentration (MIC) assays, respectively. Furthermore, the hydrolysates were also characterized with respect to yield, protein content, and degree of hydrolysis.

The produced hydrolysates showed antioxidant properties. Highest DPPH activity was obtained with Protamex, whereas highest metal chelating activity surprisingly was obtained for a control (no enzyme added). Unfortunately, no antimicrobial activity was detected for the produced hydrolysates independent of enzymes and hydrolysis time applied. BBI JU-funded WASEABI project.