Complexes of lutein with bovine and caprine caseins and their impact on lutein chemical stability in emulsion systems: Effect of arabinogalactan

Abstract

Lutein is an important xanthophyll carotenoid with many benefits to human health. Factors affecting the application of lutein as a functional ingredient in low-fat dairy-like beverages (pH 6.0-7.0) are not well understood. The interactions of bovine and caprine caseins with hydrophobic lutein were studied using UV/visible spectroscopy as well as fluorescence. Our studies confirmed that the aqueous solubility of lutein is improved after binding with bovine and caprine caseins. The rates of lutein solubilization by the binding to bovine and caprine caseins were as follows: caprine α-II-casein 34%, caprine α-I-casein 10%, and bovine casein 7% at 100 μM lutein. Fluorescence of the protein was quenched on binding supporting complex formation. The fluorescence experiments showed that the binding involves tryptophan residues and some nonspecific interactions. Scatchard plots of lutein binding to the caseins demonstrated competitive binding between the caseins and their sites of interaction with lutein. Competition experiments suggest that caprine α-II casein will bind a larger number of lutein molecules with higher affinity than other caseins. The chemical stability of lutein was largely dependent on casein type and significant increases occurred in the chemical stability of lutein with the following pattern: caprine α-II-casein > caprine α-I-casein > bovine casein. Addition of arabinogalactan to lutein-enriched emulsions increases the chemical stability of lutein-casein complexes during storage under accelerated photo-oxidation conditions at 25°C. Therefore, caprine α-II-casein alone and in combination with arabinogalactan can have important applications in the beverage industry as carrier of this xanthophyll carotenoid (lutein).

Mechanisms Governing the Transfer of Pure and Plant Matrix Carotenoids Toward Emulsified Triglycerides

“…This hypothesis explains why the transfer of pure LYC, which was not soluble in the emulsifiers, was more impaired by the emulsifiers than that of the two other pure carotenoids (Figure 5). Thus, when TG are coated with these emulsifiers, the transfer efficiency of pure carotenoids to TG results from opposite effects: negative effects due to both the quenching of the hydrophobic force by the emulsifier barrier between carotenoids and TG and to the trapping of a fraction of carotenoids by the fraction of emulsifiers that remain in the aqueous phase, and positive effects due to both the facilitated transfer of carotenoids that are incorporated in the fraction of emulsifiers located at the lipid droplet interface, and to the higher surface of exchange induced by the emulsifiers. Obviously, these hypotheses should be verified by dedicated experiments and we cannot extrapolate these observations to the effect of other dietary emulsifiers on the transfer of other carotenoid species.…”

Lutein-Enriched Emulsion-Based Delivery System: Impact of Casein-Phospholipid Emulsifiers on Chemical Stability

“…The integrity of the samples was confirmed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and the percentages of the various component caseins estimated by densitometry as previously described [22]. The casein composition of the samples is as follows: α s2 -casein (bovine casein 12.1%; caprine α s1 -I-casein 9.2%; caprine α s1 -II-casein 5.3%), α s1 -casein (type I): (bovine casein 0%; caprine α s1 -I-casein 4.0%; caprine α s1 -II-casein 0%); α s1casein (type II): (bovine casein 39.5%; caprine α s1 -I-casein 21.1%; caprine α s1 -II-casein 25.6%); β-casein: (bovine casein 37.2%; caprine α s1 -I-casein 51.6%; caprine α s1 -II-casein 60.6%); and κ-casein: (bovine casein 11.2%; caprine α s1 -I-casein 13.8%; caprine α s1 -II-casein 9.6%) [20].…”

“…Likewise, emulsions exert good protective effects on the carotenoids. Thus, it has been reported that the multilayer emulsions around the oil droplets can potentially reduce the amount of light reaching the carotenoid [19,20]. A lutein dispersion was achieved using bovine casein or caprine caseins (caprine α s1 -I-casein and caprine α s1 -II-casein) as emulsifier in an emulsion beverage [19,20].…”

“…Thus, it has been reported that the multilayer emulsions around the oil droplets can potentially reduce the amount of light reaching the carotenoid [19,20]. A lutein dispersion was achieved using bovine casein or caprine caseins (caprine α s1 -I-casein and caprine α s1 -II-casein) as emulsifier in an emulsion beverage [19,20]. The caprine casein emulsifier, in particular caprine α s1 -II-casein, in combination with arabinogalactan, a water-soluble polysaccharide, is noteworthy because this lutein dispersion system remains stable after light exposure during storage [20].…”

“…In bovine milk the constancy of the ratio of caseins results in a rather distribution of structure for casein micelles (with Ca 2+ ), which has been used for the delivery of fat-soluble bioactive compounds such as curcumin and vitamin D in aqueous solutions [17,18]. Casein sub-micelles (without Ca 2+ ) from bovine and caprine milks have been used for the delivery of lutein in food emulsions [19,20].…”