Physicochemical and functional properties of protein isolated from herring co-products; effects of catching season, pre-sorting, and co-product combination.

ABSTRACT

Effect of catching season (spring vs fall), pre-sorting and selective recombination of different herring filleting co-products on protein yield during valorisation using the alkaline pH-shift technology was studied. Impacts of the pre-processing conditions on lipid oxidation, rheological, structural and functional properties of the proteins were also investigated. The sorted frame fraction resulted in the highest protein yield, myosin content, gel-forming capacity and gel whiteness. pH-shift processing triggered severe proteolytic degradation and lipid oxidation in the head fraction imposing a low-quality protein isolate. The unsorted co-products and the combinations head + frame and head + frame + tail gave protein isolates with gelation and oxidative quality being better than head but below the isolate from frame alone. The spring co-products produced protein isolates with better overall quality than the fall co-products. Altogether, the results revealed the advantage of sorting herring co-products, and the influence of season on protein extraction from herring co-products.