Oxidative stability of whey protein-coated milkfat droplets encapsulated in wall matrices consisting of non-fat milk solids or of carbohydrates

Microencapsulation of lipids in a wall system of whey proteins (WP) has been shown to enhance the oxidative stability of lipids. To determine the contribution of the interfacially adsorbed WP film to the enhanced oxidative stability, and to evaluate the potential application of this interfacially adsorbed WP film to improve the oxidative stability of lipids in other systems, studies were conducted to establish basic understanding and applicable information pertinent to the formation, physico-chemical and functionality of whey-coated lipid droplets embedded in wall matrices of spay-dried microcapsules consisting of nonfat milk solids (NFMS) or carbohydrates.; When NFMS was used as the wall matrix, a two-step emulsion preparation method allowed establishing an interfacially adsorbed film consisting mainly of WP. Heating (90°C for 30 minute) WP-stabilized base emulsion or WP solution significantly increased adsorption of WP at oil/water interface, and reduced the displacement of the adsorbed WP by caseins after adding nonfat milk solids. Both short-term (at 50°C) and long-term (at 20 and 30°C) oxidative stability studies indicated that WP-coated lipids embedded in a NFMS matrix exhibited a significantly higher oxidative stability than casein-coated lipids embedded in the same matrix. Heating WP or base emulsion also significantly enhanced the oxidative stability of the microcapsules.; When maltodextrins or corn syrup solids were used as matrix materials, the two-step emulsion preparation method had also enhanced the adsorption of WP at O/W interface. Increasing the load of WP from 2.5% to 5%, and heating base emulsion improved the oxidative stability of the resulting microcapsules. As DE increased from 7.5 to 24, oxidative stability of microcapsules increased if they were coated only with carbohydrates, but decreased in the presence of WP.; The enhanced oxidative stability of the encapsulated WP-coated lipid indicated that the stable, continuous interfacially adsorbed films consisting of mainly WP could be established using the investigated microencapsulation techniques, that these films were effective in providing good oxygen barriers that significantly enhanced the oxidative stability of the lipids. Results of the research present new opportunities in protecting and delivering nutrients that are highly susceptible to oxidation.