Oil Gelation Ability of a Rice Bran Wax and Botanical High-Melting-Point Alcohol Mixture

Abstract

Due to its availability and relatively high melting point, rice bran wax can be used in foods and cosmetics as an oil solidifying agent. The addition of high-melting-point alcohols to the wax to optimize its performance was investigated. Such alcohols were prepared by the hydrolyzation of rice bran wax or carnauba wax. These alcohols had melting points of ～80°C, higher than that of rice bran wax, and consisted of hydrocarbons with alkyl chain lengths ranging from C24 to C34, much longer than the alkyl chains found in commercially available higher alcohols. Oil gel made with only rice bran wax as a solidifying agent has lower hardness than the conventional hydrocarbon wax gel, too low for practical usage in stick cosmetics such as lipsticks and lip creams. Blending high-melting-point alcohols with rice bran wax at 10–20% led to marked increase in gel hardness, equivalent to the gel hardness of the hydrocarbon wax. This effect on rice bran wax was not observed in commercially available higher alcohols and esters with lower melting points. Based upon the change in microstructure observed with SEM, the improved gel hardness of the rice bran wax upon addition of high-melting-point alcohols was probably induced by the disappearance of spherical clusters, originally presented in the gel, resulting in close to uniform morphology.