The casein phosphopeptide calcium chelation: preparation optimization, in vitro gastrointestinal simulated digestion and peptide fragments exploration.

Abstract

The calcium is closely related to the formation of bones and teeth, cell metabolism and other physiological activities. In this work, casein phosphopeptide-calcium chelate (CPP-Ca) was synthesized and the optimal process parameters for the chelation reaction were obtained. The bioavailability of calcium in CPP-Ca was investigated by in vitro gastrointestinal simulated digestion. The existence of phytic acid and oxalic acid in digestion system was evaluated to clarify the calcium holding ability of CPP. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) was utilized to identify oligopeptides from CPP-Ca. The optimal process parameters for the chelation reaction follows: peptide concentration 7.76 mg/mL, pH 8.54, and the reaction temperature 43.3°C. The digestion in vitro results indicated that the calcium release rate of CPP-Ca in the stomach for 2 h reached 85%, and about 50% of the ionized calcium was re-chelated with CPP in the intestine. The phytic acid and oxalic acid could lead to a sharp decrease in soluble calcium, but around 50% of the calcium was still retained in the form of chelates in the presence of CPP. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) identified nineteen casein-derived oligopeptides after digestion, and calcium modifications were found on 8 peptides derived from β-casein and αs2 -casein. The work clarified the excellent calcium holding capacity of CPP in the presence of phytic acid and oxalic acid. Furthermore, LC-MS/MS revealed peptide changes, and identified peptides with calcium chelation. These findings provided significant insights into further utilization and product development of peptide-calcium chelate in food industry. This article is protected by copyright. All rights reserved.