Stabilization of Rice Bran

Methods for stabilization of rice bran have been reviewed (37). These include dry heating, wet heating, and extrusion. The most practical method has been the use of extrusion or expansion methods. 

Rice bran oil is used in foods, feed, and industrial applications. Only high-quahty oil is targeted to foods. The use of rice bran oil in Japan, where it is the largest volume domestically produced vegetable oil, is as a frying oil where its flavor is preferred over alternative oils. The oxidative stability of rice bran oil is equivalent to peanut oil and cottonseed oils in deep frying applications (Table 18) (8, 59). 

Rhee, J and Yoon, H (1984) Stabilization of rice bran by microwave energy. Korean J. Food Sci. Technol, 161, 13-19. 

Although rice bran is still a wasted product all over the world, recent scientific studies have recognized its potential health benefits. This is a unique, nutrient-dense natural product which offers health benefits for a series of ailments. It is a food pharmacy worth considering not only for general health maintenance but also as a dietary supplement for serious health conditions. With the advent of unique stabilization technology rice bran, an under-utilized waste product, has now been made available as a highly nutritious, health-promoting food for humans. 

Unstabilized bran and polish have been used almost exclusively for animal feed, due to the bitter flavor that develops from the lipolytic action of enzymes on the oil found in them. However, development of a thermal process that inactivates the lipases has resulted in a stabilized rice bran product that is suitable for the food industry. The impressive nutritional qualities of the oil, fiber, carbohydrate and proteins of rice bran have made it a valuable food material. Removal of fiber from the bran by physical K,J7or enzymic1819 processes produces a milk-like product having desirable nutritional and functional properties. The nutritional composition of the rice bran milk product described by California Natural Products has been shown to match the nutritional requirements of an infant formula. Originally, the anti-nutritional factor of the residual phytates was of concern. However, as of 2005, phytase enzymes are suitable for use to break down these phytates. 

Refined rice bran oil is an excellent salad oil and frying oil with high oxidative stability resulting from its high level of tocopherols and from the presence of the oryzanols (ferulic acid esters of sterols and triterpene alcohols). The oxidative stability of this oil is exploited in Good Fry Oil. This is a frying oil based on oleic-rich sunflower oil to which is added up to 6% of rice bran and/or sesame oil to confer high oxidative stability. Rice bran oil also finds several nonfood uses (45). 

The instability of rice bran has long been associated with lipase activity (35). As long as the kernel is intact, lipase is physically isolated from the lipids (29). Even dehulling disturbs the surface structure allowiug lipase and oil to mix. Oil in intact bran contains 2—4-% free fatty acids (2). Once bran is milled from the kernel, a rapid increase in the FFA occurs, lu high huuiidity storage, the rate of hydrolysis is 5-10% per day and about 70% in a month as shown earlier. The objectives of rice bran stabilization are as follows ... 

The initial interest in rice bran oil resulted from work with the stabilized rice bran. Rice bran was shown to be equivalent in serum cholesterol reduction to oat bran in hamster trials (Table 15) (1). Two clinical studies showed rice bran reduced serum low-density lipoprotein (LDL) cholesterol in humans (49,50). Defatted bran was less effective in lowering cholesterol than full fat bran (1). The cholesterol-lowering activity was concentrated in the unsaponifiable fraction of rice bran oil (Table 16) (51). Oryzanol was found to contribute to the hypocholesterolemic activity of rice... 

Blends of rice bran oil with soybean oil reduces the increase in total polar material (TPM) depending on the amount of rice bran oil in the blend (Table 19). Potato chips fried in rice bran oil show flavor and odor stability at elevated temperatures between that of peanut and cottonseed oUs (Table 20). 

The addition of rice bran oil or its components as a stabilizer in frying oils has been reported (Kamal-Eldin et al., 1998 Gertz et al., 2000). Kamal-Eldin et al. (1998) reported that the addition of a blend of sesame oil and rice bran oil... 

Stabilized whole rice bran is rich in protein, lipids, dietary fiber, vitamins, essential minerals, and important nutraceuticals such as phospholipids, choline, inositol, phytosterols, tocols, and tocotrienols. Tocols and tocotrienols are potent antioxidants that reduce the risk of cancers and CVD. The whole rice bran is stabUized in order to denature lipases that cause oxidative rancidity and to protect the intrinsic nutraceutical compounds. The stabilization of the rice bran is usually done by applying heat in an extrnder. The preservation of the oryzanol is of utmost importance because this compound is very effective in promoting cardiovascular health (Hoffpauer 2005). 

Nutrient analysis of stabilized rice bran and its derivatives indicates that it is a good source of protein, dietary fiber and carbohydrates, in addition to several valuable phytonutrients, antioxidants, vitamins and minerals (Table 17.1). SRB and its water-soluble and water-insoluble derivatives contain all the nutrients at different levels. They are gluten and lactose free and do not give rise to any food allergy. 

Nutrients Macronutrients (%) Stabilized rice bran Water-soluble derivative of stabilized rice bran Water-insoluble derivative of stabilized rice bran... 

HETTiARACHCHY N s (1999) HypoaUergenicity of stabilized rice bran products. RiceX Company Report. 

QURESHI A A, SAEED A s, FAROOQ A K (2002) Effects of Stabilized rice bran, its soluble and fiber fractions on blood glucose levels and serum lipid parameters in humans with diabetes mellitus Types 1 2. J Nutri Biochem, 13 175-87. 

SHIN T, GODBER s J, MARTIN D E, WELLS H J (1997) Hydrolytic Stability and changes in vitamers and oryzanol of extruded rice bran during storage. JFood Sci, 62(4) 704-29. 

Cairoll. L.E. functional Properties and Applications of Stabilized Rice Bran in Bakery Products, Food Technology, 74 (April 1990). 

Shin and Godber (228) used a silica column and a mobile phase composed mainly of isooctane and small amounts of ethyl acetate, acetic acid, and 2,2-dimethoxypropane. The acetic acid component reduced retention times of the late-eluting E vitamers, presumably by competing with water and polar material for binding to silanol groups on the silica surface. 2,2-Dimethoxy-propane reacts with water to form acetone and methanol, and its inclusion stabilized retention times and reduced the need for column regeneration. Chromatograms of vitamin E vitamers in a standard solution and in a saponified rice bran sample are shown in Fig. 13. 

Rice bran oil can be extracted from either stabilized or unstabilized bran. The by-product resulting from stabilized bran extraction is suitable for human food use. Stabilized rice bran is currently being used in baked goods, energy bars and protein fortification of powdered drink formulations. 

Experimentally, anti-oxidants such as gallic acid, ethyl gallate, oat flour (Findlay and Smith, 1945), sorbitan monostearate, glycerol monostearate, polyoxyethylene sorbitan monostearate (Hibbs and Ashworth, 1951), ascorbyl palmitate, dodecyl gallate (Abbot, 1971), high-oryzanol rice bran oil - containing tocopherols and tocotrienols (Nanua et al, 2000), nordihy-droguaiaretic acid, butylated hydroxyanisol, butylated hydroxy toluene and citric acid (Helal et al., 1976) have been used to enhance the oxidative stability of milk powders. 

Nanua, J.N., McGregor, J.U., Godber, J.S. 2000. Influence of high-oryzanol rice bran oil on the oxidative stability of whole milk powder. J. Dairy Sci. 83, 2426-2431. 

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