title: Salting-out and salting-in: competitive effects of salt on the aggregation behavior of soy protein particles and their emulsifying properties.
abstract: Emulsions stabilized by protein particles have gained increasing research attention due to their combined advantages of biocompatibility and superior stability. In this study, colloidal particles consisting of soy protein isolates (SPIs) prepared through a heat-treatment procedure are used to make oil-in-water emulsions at a protein concentration of 10 g L(-1) and a pH of 5.91. We investigate parallelly the effects of NaCl on the stability and rheological properties of the particle suspensions and their stabilized emulsions at salt concentrations of 0, 100 and 400 mM. The aggregation behavior of the particles is strongly dependent on the NaCl concentration, showing signs of sedimentation at low NaCl concentration (100 mM) but redispersion again at high NaCl concentration (400 mM). The extensive particle aggregation is beneficial to the formation of a continuous interfacial film for the emulsions, and hence results in a remarkable increase of creaming stability and interfacial viscoelastic moduli. The results can be explained in terms of two competitive effects of NaCl: salting-out and salting-in, which are attributed to complex electrostatic interactions between the particles as a function of NaCl concentration. The delicate balance between salting-out and salting-in provides an interesting insight into the nature of underlying protein particle interactions in aqueous suspensions and a possible mechanism for tailoring their emulsifying properties via salt effects.
authors.affiliation: State Key Laboratory of Food Science and Technology, Key Laboratory of Food Colloids and Biotechnology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P. R. China. hnxujnu@163.com lianfu@jiangnan.edu.cn.
authors.forename: Hua-Neng
authors.initials: HN
authors.lastname: Xu
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Lianfu
authors.initials: L
authors.lastname: Zhang
mesh_terms: D004655:Emulsions / Q000737:chemistry; D009821:Oils / Q000737:chemistry; D010316:Particle Size; D012212:Rheology; D012965:Sodium Chloride / Q000737:chemistry*; D030262:Soybean Proteins / Q000737:chemistry* / Q000378:metabolism; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D009821:Oils; D030262:Soybean Proteins; D014867:Water; D012965:Sodium Chloride