title: Effects of ionic and nonionic surfactants on milk shell wettability during co-spray-drying of whole milk particles.
abstract: Mixing surfactants with whole milk feed before spray drying could be a commercially favorable approach to produce instant whole milk powders in a single step. Pure whole milk powders obtained directly from spray drying often have a high surface fat coverage (up to 98%), rendering them less stable during storage and less wettable upon reconstitution. Dairy industries often coat these powders with lecithin, a food-grade surfactant, in a secondary fluidized-bed drying stage to produce instant powders. This study investigated the changes in wetting behavior on the surface of a whole milk particle caused by the addition of surfactants before drying. Fresh whole milk was mixed with 0.1% (wt/wt) Tween 80 or 1% (wt/wt) lecithin (total solids), and the wetting behavior of the shell formed by each sample was captured using a single-droplet drying device at intermediate drying stages as the shell was forming. The addition of surfactants improved shell wettability from the beginning of shell formation, producing more wettable milk particles after drying. The increase in surfactant loading by 10 times reduced the wetting time from around 30s to <5s. At the same loading of 1% (wt/wt; total solids), milk particles with Tween 80 were much more wettable than those with lecithin (<5s compared with >30s). We proposed that Tween 80 could adsorb at the oil-water interface of fat globules, making the surface fat more wettable, whereas lecithin tends to combine with milk proteins to form a complex, which then competes for the air-water surface with fat globules. Spray-drying experiments confirmed the greatly improved wettability of whole milk powders by the addition of either 0.1% (wt/wt) Tween 80 or 1% (wt/wt) lecithin; wetting time was reduced from 35±4s to <15s. To the best of our knowledge, this is the first time that a dynamic droplet drying system has been used to elucidate the complex interactions between ionic or nonionic surfactants and milk components (both proteins and fat), as well as the resultant effect on the development of milk particle functionality during drying.
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, China; Department of Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: P
authors.initials: P
authors.lastname: Lallbeeharry
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Tian
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, China. Electronic address: nan.fu@suda.edu.cn.
authors.forename: N
authors.initials: N
authors.lastname: Fu
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, China. Electronic address: duo.wu@suda.edu.cn.
authors.forename: W D
authors.initials: WD
authors.lastname: Wu
authors.affiliation: Department of Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: M W
authors.initials: MW
authors.lastname: Woo
authors.affiliation: Department of Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Selomulya
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, China; Department of Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: X D
authors.initials: XD
authors.lastname: Chen
mesh_terms: D000818:Animals; D003890:Desiccation; D005511:Food Handling / Q000379:methods*; D054709:Lecithins / Q000737:chemistry; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry; D011208:Powders / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000032:analysis; D017155:Wettability
chemical_list: D054709:Lecithins; D008894:Milk Proteins; D011208:Powders; D013501:Surface-Active Agents; D014867:Water
keywords: Tween 80; lecithin; shell formation; single-droplet drying