Rice bran is by-product obtained during rice milling operation. This is golden reddish cuticle obtained after removal of the husk and during polishing of the rice. Rice bran is a mixture of substances, including protein, fat, ash, and crude fiber. In many cases, bran contains tiny fractions of rice hull, which increases the ash content of bran.
Rice bran is obtained from paddy rice in a multistage process, after harvest. The grains are submitted to the milling process, where, first, the kernel is separated from the hull (dehulling). The burnishing step is carried out to remove the brownish layer of the kernel, producing germ and bran. It is used for treating diabetes, high blood pressure, high cholesterol, alcoholism, obesity, and AIDS; for preventing stomach and colon cancer; for preventing heart and blood vessel (cardiovascular) disease; for strengthening the immune system; for increasing energy and improving athletic performance; for improving liver function; and as an antioxidant.
Rice Bran Oil –
Rice bran oil (also known as rice bran extract) is the oil extracted from the germ and inner husk of rice. Rice bran oil is also used for high cholesterol. Some people apply rice bran directly to the skin for an allergic skin rash called eczema (ectopic dermatitis). Rice bran oil, also known as Rice bran extract, is notable for high unsaturated fatty acids, Vitamin E, and Gamma Oryzanol.
Rice Bran Oil Processing –
Solvent Extraction Method –
RBO produced from solvent (normally hexane) extraction is preferred as a cooking oil, after further refinement, while the oil produced by cold pressed extraction is considered to be a superior functional oil as a dietary supplement and medicinal purposes. After solvent extraction, further refining of the rice bran oil involves degumming, neutralization, bleaching, dewaxing, and deodorizing to produce quality cooking oil, resulting in large amount of waste products left from the processes. Degumming involves the removal of phospholipids and lipoproteins through hydration by water with citric or phosphoric acid. Free fatty acids (FFAs) are removed by caustic soda (NaOH) in the neutralization process. Rice acid oil (RAO) is the major waste product from these two steps. Then, the bleaching step is applied to remove the pigments (including chlorophylls and carotenoids) of the RBO by adsorption on activated carbon or bleaching earth. A dewaxing and winterization steps follow by maintaining the oil at a low and very low temperature respectively to cause the solidified waxes and other high melting point substances as well as high melting point wax are separated as waste products.
Cold Pressed Extraction Process –
The cold pressed RBO is produced by compressing the rice bran through a mechanical screw press under mild heating (<50 °C), and the resulting oil is then filtered through filter paper, to produce the refined functional oil. Defatted rice bran and filter cake are the main by-products from this process.
During both processes, a considerable amount of by-product is produced, some of which contains more or less quantities of potential ingredients for functional food, nutraceuticals and pharmaceutical manufacture. These ingredients include mainly of γ-oryzanol, tocotrienol, tocopherol, phytosterol, lecithin, carotenoids and long-chain alcohols. Rice bran wax (RBW) is also a rich source of aliphatic primary alcohols knows as policosanols and many studies have shown that rice policosanols moderately decrease plasma cholesterol levels in hypercholesterolemia patients, reduce platelet aggregation.
Image – Flow chart of rice bran oil (RBO) production (a) RBO from solvent extraction process (b) RBO from cold pressed extraction process.
RBO is known for its high nutritional value due to the high concentrations of health beneficial bioactive compounds naturally present in the oil. Hot extraction process gets more oil yield and pure edible oil than the cold processing. It is gaining huge popularity in recent days due to its umpteen health benefits including improved heart health, regulates blood glucose and blood pressure, and prevents cancers, enhanced immunity, and skin health. Furthermore, it renders powerful antioxidant, anti-inflammatory and anti-cancer effects, so reap the wellness incentives by adding this nourishing oil in your regular cooking.