Rice (Oryza sativa L.) consists of 18 to 28% hull and the edible portion (brown rice). After the hull is removed, the resulting brown rice is further processed by abrasive milling, which removes 6 to 10% of the weight as bran polish. The remainder is known as white or milled rice. Conventional and Japanese rice milling systems consist of pre-cleaning, dehulling, rough rice separation, and whitening (16); the chemical composition of rice and its fractions have been listed (17). Brown rice and white rice are usually consumed as food after cooking. Rice bran, because of rancidity problems, was used exclusively as animal feed until recently. Stabilized rice bran is now commercially available in the United States, and perhaps 1% of rice bran in the United States, is used as human food.

Rice is a staple diet item in half of the world's population, but only a relatively small proportion of adverse food reactions are from rice proteins. The main allergen of rice is the 16-kDa globulin, and rice mutants containing low levels of the 16-kDa allergenic protein were obtained by y-ray irradiation or ethyl methanesulfonate treatment (18). Another method to make hypoallergenic rice is to digest the allergenic protein with a proteolytic enzyme, Ac-tinase (19).

OATS Processing

Oat (Avena sativa L.) processing includes cleaning, de-hulling, steaming, and flaking (20). Typical products from milling oats are rolled oats, oat hulls, feed oats, mixed grains and seeds, and fines. Oats are dry milled into break flour, reduction flour, shorts flours, shorts, bran, and hulls (21). Weight distribution and protein contents of dry-milled oat fractions, sequential solvent extraction of proteins from milled fractions, and amino acid compositions of milled fractions and oat extracts were also determined (21). Several commercial high-protein oat cultivars are available. Protein concentrates have been prepared from oat groats (dehulled oats) by wet-milling procedures (22). Air classification (separation of particles by size in a stream of air) of oat groats can concentrate protein in the fine fraction and concentrate /?-glucan, a polysaccharide that can lower elevated serum cholesterol in humans, in the coarse fraction (23). Amylodextrins with soluble fi-glucan contents as high as 10% were prepared from milled oat flours and brans by a-amylases treatment (24). These amylodextrins are used as fat substitutes in bakery goods, dairy products such as cheese, and beverages. Estimated production of oat amylodextrins was around 5 million lb in 1998.

Nutrient Composition of Oat Products

The nutritional quality of oat protein is good compared with other cereals; rolled oats have a protein efficiency ra tio (PER) of 2.2 compared with the milk protein casein with a PER of 2.5. Oat groats used for food contain 11 to 15% protein. However, some dehulled oats from the Near East have protein contents of up to 25%.

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