Functional properties of protein-rich ingredients recovered from brown crab side streams via mechanical separation vs pH-shift processing

Journal article, 2026

The effects of steam cooking, cleaning (i.e., carapace and viscera removal), mechanical separation (MS), and alkaline pH-shift processing on mass yield from clawless, poorly filled brown crab were evaluated together with the structural, dynamic rheological, and functional properties of the resulting protein-enriched ingredients. Mechanical separation of cooked crab resulted in the highest mass yield (57-60% w/w based on the input biomass) but yielded the lowest protein functionality. In contrast, pH-shift processing enabled more efficient protein concentration (10-14% wet weight basis) than MS (8-9% wet weight basis) due to improved shell removal; however, this method was only applicable to raw crab due to the heat-induced protein denaturation reducing its solubility. Protein denaturation in cooked material and proteolytic degradation in non-cleaned crab significantly impaired gel-forming capacity in ingredients obtained by both processing routes. Ingredients produced by pH-shift processing of cleaned raw crab exhibited a threefold higher gel-forming capacity (164 g vs 54 g, respectively) and significantly improved water-holding capacity compared with MS-derived proteins. Overall, valorization of clawless, poorly filled brown crab into protein-enriched ingredients represents a viable strategy to reduce biomass losses in crab fisheries. Nevertheless, appropriate combinations of biomass pretreatment and processing methods must be selected according to the intended ingredient functionality.