Protein-based carriers for food bioactive delivery: gastrointestinal barriers, structural design, and...

Poor gastrointestinal stability and inefficient intestinal absorption remain major bottlenecks limiting the nutritional efficacy of food bioactives. Although protein-based carriers are widely investigated because of their edible origin, biodegradability, structural diversity, and tunable assembly behavior, many studies still emphasize material-level parameters rather than bioavailability-relevant performance. This review re-examines protein-based oral delivery systems through a gastrointestinal barrier-oriented framework. Representative carriers, including plant prolamins, legume globulins, oilseed and tuber proteins, albumins, milk proteins, fibrous proteins, ferritin cages, virus-like particles, elastin-like polypeptides, and silk fibroin, are discussed according to their structural features, assembly behavior, digestion fate, and delivery functions. Particular attention is given to how protein architectures can be engineered to improve gastric protection, protease resistance, mucus penetration, epithelial interaction, regional retention, and controlled release. Rather than treating protein source as the primary determinant of delivery performance, this review highlights carrier-barrier compatibility as the central design principle. Current evidence suggests that effective systems increasingly require integrated functions, including colloidal stability, food-grade manufacturability, safety, sensory compatibility, and measurable bioavailability enhancement. Future development should move beyond proof-of-concept encapsulation toward standardized digestion-absorption models, quantitative in vivo evaluation, and scalable processing strategies suitable for functional foods and dietary supplements.