Everything You Need to Know About Oryza Sativa Rice Bran Wax

What is Oryza Sativa Rice Bran Wax?

Oryza sativa rice bran wax also called rice bran wax, is the waste of rice bran oil processing by refining the product[1-3], by many kinds of different carbon chain length fatty alcohol and fatty acid combination and becoming the ester mixture, rice bran wax molecular carbon chain length distribution range is C44 ~ C62, rice bran wax fat alcohol molecular weight is 430 ~ 460, fatty acid molecular weight is 340 ~ 360[4-6]. The research on the composition of rice bran wax began in the twentieth century in the twentieth generation, and with the application of chromatographic separation technology in lipid analysis, there was a big breakthrough in the seventies. Japan Iwama, Takamoto and Rock (Tulloch) and so on successively analyzed the carbon number composition of alcohol and acid homologue in rice bran wax, carried out the determination of carbon number, and made people have a clearer understanding of the composition of rice bran wax[7-9].

1.Physical Properties of Oryza Sativa Rice Bran Wax

Refined rice bran wax is a white or light yellow solid, the specific gravity of rice bran wax is 0.97 in the solid state at room temperature, its expansion coefficient is 0.00064 in the liquid state at room temperature, and 0.00111 in the solid state; rice bran wax has a certain hardness, and the melting point is higher (78~83℃), and there is no viscosity. The gloss of rice bran wax is very good and it has electrical insulation properties. At room temperature, the solubility of oryza sativa rice bran wax in organic solvents is very low, at 20℃, the solubility in petroleum ether, six solvents and toluene is 1.0%~3.5%, and the solubility in methanol, isopropyl alcohol, 95% ethanol, butanol, hexane, acetone, and benzene is even lower, only 0.1%~0.86%. Meanwhile, the solubility gradually increases with increasing temperature [10-13].

2. Chemical Properties of Oryza Sativa Rice Bran Wax

Rice bran wax is an ester mixture mainly composed of higher fatty acids and higher monohydric alcohols (also containing trace amounts of hydrocarbon compounds). The saponification value of rice bran wax is usually 72-80; The iodine value is relatively low, between 17 and 20; The acid value is 1-4; The content of unsaponifiable substances in rice bran wax is 54-60%; The acetyl value of rice bran wax is 3-5. In addition, rice bran wax, as an ester, can be hydrolyzed, but it is difficult and can only be carried out in alkaline media. Its hydrolysis process is slower and more difficult than that of oil, and it cannot be completely decomposed in acidic media [14-17].

3. Melting Point of Rice Bran Wax

Rice bran wax is a light yellow lump. Slightly rice bran odor. Melting point 60~85℃. Can be mutually soluble with all kinds of natural wax arbitrarily. Insoluble in water, insoluble in ethanol, hot soluble in xylene and trichloroethylene, benzene, and other organic solvents.

4. Oryza Sativa Rice Bran Wax Composition

Oryza sativa rice bran wax is different from Brazilian carnauba wax and beeswax in that it contains double esters, triple esters, and diol esters, etc. Its composition is relatively single, with most of the wax esters composed of even-carbon number long-chain fatty acids and even-carbon number long-chain aliphatic monobasic primary alcohols, and relatively few other components [18-19]. Due to the differences in the processing methods of rice bran wax, the composition of the wax is inconclusive, and there are many studies on its composition in China and abroad, but there is no uniform conclusion [20-23].

Wang Yun et al. analyzed the composition of fatty acids and fatty alcohols in rice bran waxes of different origins by gas chromatography and concluded that the carbon number of fatty acids in bran waxes ranges from C14 to C36, which is much longer than that of fatty acids in general animal and vegetable fats and oils. Among them, even carbons account for about 95%, C22 and C24 fatty acids are the main fatty acids, and the sum of these two fatty acids accounts for about 60%. And contains a small amount of unsaturated fatty acids, among them are C18 monoolefin, diene and trienoic acid as, its content with the rice bran wax refining degree to improve and reduce. In the crude rice bran wax, the total content of C18:1, C18:2 and C18:3 is as high as 28-61%, which is mainly due to the high oil content in the crude rice bran wax and the high content of oleic acid and linoleic acid in the rice bran oil. The fatty alcohol carbon number distribution range of rice bran wax is C22-C38, even carbon alcohol accounts for about 95%, and the content of thirty alcohol is the highest. Fatty acid carbon number distribution range is C14-C36, even carbonic acid accounts for about 95%, and C24 acid content is the highest, accounting for more than 40% [24-25].

5.  Oryza Sativa Rice Bran Wax Manufacturing Method

1) Taking wax oil as raw material, adopt a saponification method, wax oil first by bagging presses, remove most of the oil and grease, obtain the gross wax, then carry on the saponification of the gross wax, washes, dehydrate, then decolors the treatment to obtain the fine bran wax. The advantage of this method is simple production equipment, and low investment; shortcomings are also obvious, labor intensity, and low wax yield. At the same time because of the wax with neutral oil saponification, resulting in more soap and washing liquid, easy to cause environmental pollution.

2) Take wax oil or wax as raw material and adopt the solvent extraction method. This method improves the rate of oryza sativa rice bran wax and its oil use value, improves the labor conditions, and prevents and reduces the pollution to the environment; However, the required production equipment investment is large.

6. Application of  Oryza Sativa Rice Bran Wax

Rice bran wax can be used as a substitute for Brazilian carnauba wax in most applications due to its relatively high melting point. It is used in paper coatings, textiles, explosives, fruit and vegetable coatings, confectionery, pharmaceuticals, candles, molded novelties, electrical insulation, textile and leather sizing, waterproofing, copy paper, typewriter ribbons, printing inks, lubricants, crayons, adhesives, chewing gum and cosmetics.

In cosmetics, oryza sativa rice bran wax is used as an emollient and is the base material for some exfoliating particles. It has been found that at concentrations as low as 1% triglyceride, rice bran wax can crystallize to form a stable gel.

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