Membrane-based fractionation, enzymatic dephosphorylation, and gastrointestinal digestibility of β-casein enriched serum protein ingredients

Abstract This study aims to produce a serum protein ingredient enriched with dephosphorylated β-casein from skim milk for infant formula manufacture using ceramic membrane filtration combined with enzymatic dephosphorylation. Compared to filtration at 25 °C or using skim milk ultrafiltration permeates as a diafiltrant, filtration at 4 °C using water as a diafiltrant improved the selective co-enrichment of β-casein with whey proteins in the permeates, resulting in a serum protein ingredient with 49% β-casein, 45% whey proteins and 6% of other caseins after microfiltration and 4-stage diafiltration. Subsequent incubation with phosphatase achieved 0–97% casein dephosphorylation, and β-casein showed multi-dephosphorylated isoforms depending on dephosphorylation extent. With increased dephosphorylation, β-casein enriched serum protein ingredients formed looser gastric clots with greater gastrointestinal digestibility under infant in vitro model conditions. These results offer a potential to develop a multi-functional serum protein ingredient with a casein profile (composition/phosphorylation) close to human milk for use in infant formula.