Chitosan oligosaccharides-tripolyphosphate microcapsules as efficient vehicles for desalted duck egg white peptides-calcium: Fabrication, entrapment mechanism and in vivo calcium absorption studies

Microcapsules based on food-grade biopolymers are of particular interest for biological components delivery owing to their unique controlled release property. In present study, a novel calcium delivery system was obtained by gelation interaction of chitosan oligosaccharides (COS) with tripolyphosphate (TPP), and desalted duck egg white peptides-calcium (DPs-Ca) chelate was encapsulated to fabricate TPP-COS/DPs-Ca microcapsules. The solution containing 4% COS and 1.76% TPP, TPP pH of 9, and COS: DPs<1k -Ca ratio of 2:1, resulted in calcium content of microcapsules was 22 mg/g. The intermolecular forces, morphology characterizations, controlled calcium release and calcium absorption properties in vitro and vivo of microcapsules were investigated. The resulted showed that, material wall (COS) could prevent DPs-Ca avoiding stomach digestion and lead more calcium to enter the intestine, thus to promote calcium absorption. In low-calcium diet-induced calcium deficiency mice model, the analysis of serum indexes, bone indexes and micro-CT of bone trabeculae in mice revealed that TPP-COS/DPs-Ca could promote the absorption of calcium in enterocyte of the body, then to reduce the risk of osteoporosis and improve gut health. Overall, these results confirmed the potentialities of TPP-COS/DPs-Ca as nutraceuticals/functional food for oral calcium delivery to promote calcium absorption and improve gut health.