Dept. of Product Development, Faculty of Agro-Industry, Kasetsart Univ., Bangkok, Thailand.
J Food Sci. 2011 Jan-Feb;76(1):E165-72. doi: 10.1111/j.1750-3841.2010.01959.x. Epub 2011 Jan 6.
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.
米糠油（RBO）因其良好的健康、风味和功能特性，被广泛应用于食品、化妆品和制药领域。我们研究了生物聚合物乳化剂类型和环境应激对 RBO 乳液稳定性的影响。采用高压均质法制备了乳清蛋白分离物（WPI）、瓜尔胶（GA）或改性淀粉（MS）稳定的水包油（5% RBO、10mM 柠檬酸盐缓冲液）乳液。所使用的新型 MS 每淀粉分子的辛烯基琥珀酸酐（OSA）基团数量高于传统 MS。WPI 和 MS 产生的液滴直径明显较小（d < 300nm），而 GA 产生的液滴直径较大（d > 1000nm）。研究了 pH（3 至 8）、离子强度（0 至 500mM NaCl）和热处理（30 至 90°C）对乳液物理稳定性的影响。在等电点（4 < pH < 6）、高盐（> 200mM，pH 7）和高温（> 70°C，pH 7，150mM NaCl）下，WPI 稳定的乳液中发生了广泛的液滴聚集，这归因于液滴之间静电和疏水相互作用的变化。GA 或 MS 稳定的乳液受 pH、离子强度和温度的影响较小，这归因于强大的空间稳定作用。综上所述：WPI 在低浓度下产生小液滴，但对环境应激的稳定性较差；GA 产生大液滴且需要高浓度，但对应激的稳定性较好；新型 MS 在低浓度下产生小液滴，对应激的稳定性较好。实际应用：本研究表明，可使用生物聚合物乳化剂形成稳定的米糠油/water 乳液。这些乳液可用于将 RBO 掺入各种食品产品中。我们比较了乳清蛋白、GA 和新型 MS 形成和稳定乳液的相对性能。新型 OSA MS 能够在相对较低的浓度下形成小而稳定的液滴。
