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.

Formation, antioxidant property and oxidative stability of cold pressed rice bran oil emulsion

“…The fact that the droplets have a high negative charge is important for certain applications, since it affects the physical and chemical stability of emulsions (Karraker and Radke 2002;McClements 2005). The CPRBO emulsions stabilized by GMS had larger negative zeta potential than RBO emulsions stabilized by whey protein, gum Arabic, or modified starch (Charoen et al 2011) or by Tween 80 and Span 80 (Nguyen et al 2013). This may have been due to differences in the type of ionized species adsorbed at the oil-water interface, or due to differences in solution properties (such as pH and ionic strength).…”

Progress in natural emulsifiers for utilization in food emulsions

“…Consequently, polysaccharide-stabilized emulsions tend to be relatively stable to changes in pH (Figure 4), ionic strength, and temperature [22,23,39,46]. Nevertheless, many polysaccharides have some electrical charge, which may impact their ability to interact with other charged substances, such as transition metals, colloidal particles, or biopolymers.…”

Effects of antioxidants on the stability of β-Carotene in O/W emulsions stabilized by Gum Arabic

“…It consists mainly of a mixture of arabinogalactan (AG) (80-90 % of the total gum in weight), glycoprotein (GP) (2-4 % of the total gum in weight) and arabinogalactan protein (AGP) (10-20 % of the total gum in weight) fractions (Bouyer et al 2011). Previous studies showed that gum arabic was widely used in preparation of emulsions, and the droplet characteristics were then evaluated (Jayme et al 1999;Djordjevic et al 2007Djordjevic et al , 2008Karaiskou et al 2008;Padala et al 2009;Bouyer et al 2011;Charoen et al 2011;Zhang and Liu 2011). However, no information is available concerning the effect of antioxidants on the stability of β-carotene in the emulsions stabilized by gum arabic.…”