An Update on the Use of Co-products from the Milling of Rice in Value-Added Food Products

Because of the large amount of rice produced annually, milled rice co-products, such as rice flour, rice bran, rice bran oil, wax, and rice hulls are plentiful and readily available. These co-products are valuable sources of food ingredients, but they are currently under-utilized. Rice bran and flour contain different levels of protein. When treated with carbohydrate-hydrolyzing enzymes, high-protein products can be produced, which are nutritious and used widely in health and baby food formulations. Recently, subcritical water processing has also been studied, in which water is put under high pressure to maintain its liquid state and used as an environmental-friendly media for the recovery of rice bran proteins. Rice flour contains more than 90% rice starch (RS), and functional properties of RS are normally modified to suit the needs for food applications. For example, the addition of small amounts of phosphorylated RS esters or pregelatinized rice flour to frying batters made of rice flour was found to impart superior sensory characteristics and lower the amount of oil-uptake. Reductions in oil uptake of up to 50% were observed with the rice based formulations compared with batters made from traditional wheat ingredients. Treatment of RS with octenylsuccinic anhydride produces modified starch products that are useful as an emulsifying agent for the encapsulation of lipophilic compounds. Similarly, other rice-based products, such as microcrystalline celluloses from rice hulls, edible films formed with rice wax, various components with antioxidant properties, and germinated brown rice flours have also been developed.