Calcium binding affects in vitro gastrointestinal digestion of bovine α-lactalbumin under infant, adult and elderly conditions

Abstract

α-Lactalbumin bound with negligible, one and two Ca2+ ions (apo, holo-Ca and holo-2Ca La) were prepared, and thermal stability and gastrointestinal digestibility under infant, adult and elderly conditions were studied. Holo-2Ca La was prepared by adding 1.5 mol Ca mol−1 La to holo-Ca La solution. Almost complete release of bound Ca from holo-Ca La was achieved at pH 2.0. Bound Ca was limitedly released from holo-Ca La using citrate, and was readily released using EDTA especially at alkaline pH. Apo La was prepared by 5 stages of 4× ultrafiltration of holo-Ca La solution with 8 mol added EDTA mol−1 La at pH 8.0, where the bound Ca2+ ion remained at 0.03 mol mol−1 La. Thermal stability increased in order of apo, holo-Ca and holo-2Ca La. Infant gastrointestinal digestibility increased in order of holo-2Ca, holo-Ca and apo La. Digestibility of apo La increased in order of infant, elderly and adult conditions.