Two novel calcium delivery systems fabricated by casein phosphopeptides and chitosan oligosaccharides: Preparation, characterization, and bioactive studies

Calcium delivery systems based on natural products such as proteins and polysaccharides, for improving calcium bioavailability, were of particular interest for food applications. Here, two novel delivery vehicles based on casein phosphopeptides (CPP) and chitosan oligosaccharides (COS) were prepared, characterized, and evaluated. These delivery vehicles were prepared via Amadori-type reactions and TGase-catalyzed reactions. Particle size and zeta potential determinations results showed that the particle size of two delivery vehicles significantly increased and the solution stability not decreased. Besides, the calcium release time of two nano-carriers significantly increased. Fourier transform infrared spectroscopy (FTIR) indicated that the chemical grafting of Amadori-type copolymer generated in -NH2 of CPP and C=O of COS, while TGase-type copolymer in -NH2 of CPP and -NH2 of COS. Structural characterizations revealed COS exerted a screening effect to protect CPP from the aqueous phase. Additionally, Caco-2 cells model demonstrated that two delivery vehicles could enhance intestinal calcium absorption. Serum and bone parameters exhibited that two delivery vehicles could enhance the calcium retention and bone synthesis. Gut microbiota environment was regulated in a prebiotic-like manner, and some microbial metabolite like butyric acid increased. Therefore, two calcium delivery systems could not only function as novel calcium supplements, but also protect gut health.