Rice is one of the oldest cereal grains, and has its origins in China more than five thousand years ago. It is a staple food source throughout the world, particularly for people living in Asia. White rice is the most commonly consumed type, but brown rice is gaining popularity because of its high fiber content and other nutritional and health benefits.
Rice from the field is enclosed in a tough outer hull which needs to be removed. Underneath is a nutritious whole grain, which is usually brown. All rice can be eaten at this stage, but most times it is processed further. Under the hull are the bran and the germ which are high in vitamins, minerals, and oils. Remove the bran and the germ and what is left is the endosperm, the white rice that most of us know. To replace some of the nutrients lost in processing, processors apply a thin vitamin rich coating and call it enriched rice.
Various food products are made from rice, including rice flour, rice syrup, rice bran oil, and rice milk. Rice is composed of mainly carbohydrates in the form of starch and small amounts of protein and almost no fat. Like all grains, rice can also be used to make alcoholic beverages.
The processing of rice involves multiple steps, which are categorized here in general terms. After harvesting, the rice has to be pre-cleaned and dried to a moisture content of 20%. De-hulling of the rice is done mechanically with a shelling machine that removes 90% of the hulls. Hulled rice is commonly known as brown rice. Since the bran layers are still intact, further processing is required to remove them. Additional hulling machines abrade away the bran layers to reveal the endosperm or what we know as white rice. The lightened rice is polished to produce a smooth finish. The rice is then coated with vitamins and minerals to restore nutrients.
Rice hulls are used in a wide variety of food and industrial applications. In addition to being used as a source of fiber in foods, rice hulls are used as a pellet binder in animal feed, fiber to add structural strength in injection molding and extrusion processes, and is also a substitute for products containing wood fiber, wood flour, or wood shavings. A Mikro Pulverizer Hammer Mill system can be used to grind rice hulls down to a particle size of 35% < 100 mesh (150 microns) or finer. Secondary screenings allow the capability to make different particle size distributions.
Rice flour also has many uses. Rice flour is a good substitute for wheat flour, which causes irritation in the digestive systems of those who are gluten-intolerant. Rice flour is also used as a thickening agent in recipes that are refrigerated or frozen since it inhibits liquid separation. Rice is milled into rice flour with the Mikro ACM Air Classifying Mill to a particle size of 100% < 80 mesh (180 microns).