Construction and stability evaluation of a novel Amadori-type dextran-casein phosphopeptide-Ca²⁺ delivery system

Calcium bioavailability is substantially reduced during digestion due to interactions with food components that promote precipitation as insoluble salts in the gastrointestinal environment. The aim of this paper is to construct an efficient and stable Amadori-type DEX-CPP-Ca²⁺ delivery system using casein phosphopeptide (CPP) and dextran (DEX). Optimal calcium binding capacity (15.39 mg/g, p < 0.05) was achieved under a CPP: DEX mass ratio of 1:3, pH 8.0, and heating at 90 °C for 3 h. The DEX-CPP-Ca²⁺ system effectively inhibited phosphate precipitation, maintained structural stability with sustained calcium release throughout in vitro digestion, and enhanced calcium uptake efficiency in Caco-2 cell models. Furthermore, the system exhibited exceptional stability across broad ranges of pH (2.0-9.0), temperature (0-100 °C), sugar concentrations (glucose, fructose, lactose, sucrose), and NaCl concentrations (0.5-1.3 % w/v). Structural characterization revealed successful cross-linking among DEX, CPP, and Ca²⁺, resulting in a more compact and regular morphology stabilized by hydrogen bonds. The DEX-CPP-Ca²⁺ delivery system provides a novel strategy to overcome food interference in dietary calcium absorption.