title: Influence of biopolymer emulsifier type on formation and stability of rice bran oil-in-water emulsions: whey protein, gum arabic, and modified starch.
abstract: Rice bran oil (RBO) is used in foods, cosmetics, and pharmaceuticals due to its desirable health, flavor, and functional attributes. We investigated the effects of biopolymer emulsifier type and environmental stresses on the stability of RBO emulsions. Oil-in-water emulsions (5% RBO, 10 mM citrate buffer) stabilized by whey protein isolate (WPI), gum arabic (GA), or modified starch (MS) were prepared using high-pressure homogenization. The new MS used had a higher number of octenyl succinic anhydride (OSA) groups per starch molecule than conventional MS. The droplet diameters produced by WPI and MS were considerably smaller (d < 300 nm) than those produced by GA (d > 1000 nm). The influence of pH (3 to 8), ionic strength (0 to 500 mM NaCl), and thermal treatment (30 to 90 °C) on the physical stability of the emulsions was examined. Extensive droplet aggregation occurred in WPI-stabilized emulsions around their isoelectric point (4 < pH < 6), at high salt (> 200 mM, pH 7), and at high temperatures (>70 °C, pH 7, 150 mM NaCl), which was attributed to changes in electrostatic and hydrophobic interactions between droplets. There was little effect of pH, ionic strength, and temperature on emulsions stabilized by GA or MS, which was attributed to strong steric stabilization. In summary: WPI produced small droplets at low concentrations, but they had poor stability to environmental stress; GA produced large droplets and needed high concentrations, but they had good stability to stress; new MS produced small droplets at low concentrations, with good stability to stress. Practical Application: This study showed that stable rice bran oil-in-water emulsions can be formed using biopolymer emulsifiers. These emulsions could be used to incorporate RBO into a wide range of food products. We compared the relative performance of whey protein, GA, and a new MS at forming and stabilizing the emulsions. The new OSA MS was capable of forming small stable droplets at relatively low concentrations.
authors.affiliation: Dept. of Product Development, Faculty of Agro-Industry, Kasetsart Univ., Bangkok, Thailand.
authors.forename: Ratchanee
authors.initials: R
authors.lastname: Charoen
authors.forename: Anuvat
authors.initials: A
authors.lastname: Jangchud
authors.forename: Kamolwan
authors.initials: K
authors.lastname: Jangchud
authors.forename: Thepkunya
authors.initials: T
authors.lastname: Harnsilawat
authors.forename: Onanong
authors.initials: O
authors.lastname: Naivikul
authors.forename: David Julian
authors.initials: DJ
authors.lastname: McClements
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage; D045703:Emulsifying Agents / Q000737:chemistry*; D004655:Emulsions; D004951:Esterification; D005503:Food Additives / Q000737:chemistry; D005527:Food, Fortified / Q000032:analysis; D006170:Gum Arabic / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008894:Milk Proteins / Q000737:chemistry*; D012275:Oryza / Q000737:chemistry*; D009994:Osmolar Concentration; D010938:Plant Oils / Q000737:chemistry*; D000073879:Rice Bran Oil; D012639:Seeds / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D013213:Starch / Q000031:analogs & derivatives* / Q000737:chemistry; D000067816:Whey Proteins
chemical_list: D000975:Antioxidants; D045703:Emulsifying Agents; D004655:Emulsions; D005503:Food Additives; D008894:Milk Proteins; D010938:Plant Oils; D000067816:Whey Proteins; C551966:octenyl succinic anhydride-modified starch; D012965:Sodium Chloride; D006170:Gum Arabic; D013213:Starch; D000073879:Rice Bran Oil