Creating functional protein ingredients by cross-processing herring co-products with lingonberry press-cake, shrimp shells, or green seaweed.

Other conference contribution, 2022

Cross-processing herring co-products with lingonberry press-cake, shrimp shells and green seaweed (hereafter referred to as "helpers") was recently reported to mitigate lipid oxidation during pH-shift-based protein isolation but had the drawback to reduce protein yield. Here, four strategies to counteract this yield-reduction were studied; optimized solubilization and precipitation pHs, increased water to raw material ratio as well as application of high shear mechanical homogenization (HSMH) and ultrasonication (US). Beyond effects on protein yield, the impacts of the process conditions on the structural, rheological and functional properties of the recovered proteins were also investigated.Increasing solubilization pH from 11.5 to 12 and decreasing precipitation pH from 5.5 to 5.0 or 4.5, as well as increasing the water-to-raw material ratio significantly improved protein yield with all helpers. Rotor-stator (RS)-HSMH and US also improved protein yield by 5-12% with a more marked effect of the type of helper.

Cross-processing herring co-products with antioxidant-rich helpers substantially improved water solubility and emulsification capacity of the protein isolates but the effects of RS-HSMH and US were highly dependent on the type of helper. RS-HSMH helped in mitigating the observed negative impact of cross-processing on gel-forming capacity of protein isolates produced in presence of all three helpers; results with lingonberry press-cake were particularly promising. Altogether, tuning processing conditions as well as adding RS-HSMH and US can help in maximizing protein yield during cross-processing of herring co-products with antioxidant-containing helpers. However, the effects of processing conditions on protein functionality are intimately linked to the type of helpers. The combination of herring co-products with lingonberry press-cake was the most promising and will be subject for further studies.