Shrimp processing methods profoundly alter protein structure and digestibility, with raw-frozen preserving nutritional value

Optimizing the nutritional value of seafood, particularly protein digestibility, is a key challenge in food science. Shrimp is a globally consumed protein source, but its processing methods can drastically alter its protein structure and subsequent bioavailability. Current understanding of how common processing techniques — such as freezing, cooking, and drying — mechanistically impact the multi-scale digestive behavior of shrimp muscle protein is limited. This knowledge gap hinders the development of processing strategies that enhance, rather than compromise, the nutritional quality of shrimp protein, affecting consumer health and food industry practices.

Researchers systematically investigated the impact of four processing methods on Litopenaeus vannamei muscle protein: fresh (FB), raw-frozen (RFB), cooked-frozen (FCB), and dried (DB). An in vitro dynamic gastrointestinal digestion model was employed to simulate human digestion. Multi-scale analytical techniques, including SDS-PAGE for protein degradation, endogenous fluorescence spectroscopy for protein unfolding, particle size distribution and confocal laser scanning microscopy (CLSM) for structural changes, and peptidomics for peptide release and cleavage sites, were used to assess digestive properties.

Processing methods significantly altered protein structure, enzymatic resistance, and digestive product characteristics. SDS-PAGE revealed persistent MHC bands in DB samples throughout gastric digestion, whereas FB and RFB exhibited complete degradation. Endogenous fluorescence spectroscopy indicated that processing generally inhibited the unfolding of proteins during gastrointestinal digestion, suggesting reduced accessibility for enzymes. Particle analysis and CLSM confirmed that the DB group still presented large, dense, and insoluble residues after gastrointestinal digestion. Severe dehydration in dry-heat treatment formed dense and stable protein aggregates that markedly hindered pepsin and trypsin penetration, resulting in the lowest digestion efficiency across all methods. Peptidomics further revealed that myosin and actin were the primary peptide sources, with over 80% of cleavage sites located in helix structures. The raw-frozen samples better preserved protein digestibility and nutritional value.

Raw-frozen shrimp samples demonstrated superior protein digestibility compared to cooked-frozen or dried counterparts, indicating better preservation of nutritional quality.