Dehulling

Magnets, Aspirators, Screening, Disk Separators and Gravity Tables 

FIGURE 7.6 Flowchart of the typical dry-milling process of rice. Photograph depicts, from top to bottom and left to right, rough rice, rice hulls, brown rice, bran, head rice, second head, broken rice and rice flour. 

Rice bran has little use as a source of dietary fiber unless the fat is ranoved with hexane. Rice bran is approximately 20% oil rich in monounsaturated and polyunsaturated fatty acids (Table 7.3). These unsaturated fatty acids are prone to oxidative rancidity. In Asia and other rice-producing regions, rice oil is frequently obtained from rice bran. 

Milling Yields and Chemical Composition of Dry-Milled Products of Rice 

Nutrient Paddy Brown Grits Flour Bran 

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Data vary with efficiency of dehulling and oil extraction, variety of seed, and climatic conditions during growth. Red skins or testa. 

In order to produce soy protein, soybeans are first dehulled, flaked, and defatted to make white flakes . Soy protein concentrates are obtained by removing a portion of the carbohydrates from defatted and dehulled soybeans. Alcohol extraction is the method most commonly used to manufacture soy protein concentrates even though it results in the loss of isoflavones. Soy protein concentrates retain most of the fiber in the original soybean and must contain at least 65% protein on a moisture-free basis to meet quality standards. The most concentrated source of soy protein is soy protein isolates (or isolated soy protein, ISP), which is required to be at least 90% protein on a moisture-free basis. It is heat-treated during processing to insure inactivation of trypsin inhibitors. Most isolated soy protein is manufactured by water extraction from defatted and dehulled soybeans and it retains the natural isoflavones. 

The Water Unextractable Solids were isolated from dehulled, defatted, untoasted soy bean meal (particle size < 0.5 mm) by removal of cold water solubles, proteins and starch. The soy bean meal was extracted with cold water, a solution containing sodium dodecylsulphate and 1,4-dithiothreitol, and incubated with a-amylase, to yield the CWS, SDSS and HWS... 

In the USA, specially treated oat bakery ingredients are produced by heating the grain to 100°C with steam and leaving the grain in silos for 12 hours. This process conditions the oats so that they can then be dehulled. 

Protein content of dehulled Trapper field peas is negatively correlated with the amino acids threonine, cystine, glycine, alanine, methionine, and lysine and positively correlated with glutamic acid and arginine (8). Holt and Sosulski (19) obtained similar correlations with Century field peas for all amino acids except glutamic acid. Other investigators (20) also found that sulfur amino acids (cys, met) are negatively correlated with protein content. 

The predominant polysaccharide in dehulled field pea flour is starch (49.7-59.8%) and the major soluble sugars are a-galactosides (4.78%) and sucrose (1.85-2.2%) (8,23,24). Verbascose is the major a-galactoside present in field pea flour (23,24). The a-galactosides are the main contributors to the flatulence caused by ingestion of legume flours. 

Preparation. Traditionally, soaked, hand-dehulled and briefly boiled soybeans are inoculated with small pieces of tempeh from a previous fermentation, wrapped in banana leaves which also serve as a source of inoculum, then left at room temperature for 1-2 days. 

Dehulled full-fat soybean grits -Tap water Soaked 30 min. at 25 C... 

The smooth field pea (Pisum sativum L. cv. Trapper) and small fababean (Vicia faba minor cv. Diana) samples were composites of several lots grown in 1981. After blending, about 20 kg were dehulled on a resinoid disc, abrasive dehuller (19), followed by air aspiration to remove 10 and 15% of hulls, resp. The dehulled seeds were coarse-ground in a hammermill and subdivided for dry and wet processing. 

Composition of legume flours. Proximate analyses of the dehulled flours of field pea and fababean (Table I) showed that the raw materials were typical of legume flours processed by previous investigators (3,8,24) but Colonna et al. (6) and Vose et al. (9) utilized field pea samples with higher concentrations of crude... 

Table I. Concentration of proximate constituents and carbohydrates in flours, dry and wet processed products from dehulled field pea and fababean, % dry basis.

Dry beans (Phaseolus vulgaris), represented by the commercial classes of navy, pinto and black were used to produce flour fractions at the Food Protein Research and Development Center, Texas A M University. Beans were dry-roasted under selected process conditions in a gas fired solid-to-solid heat exchanger, dehulled by air aspiration, pin-milled and air-classified to obtain four flour fractions. These fractions included whole, hulls, high protein, and high starch flours. 

Radioprotective effect. Rice seeds of cul-tivars Katakutara and Kusabue, kept in the seed hull and irradiated with y-radiation, showed greater germination than those that had been dehulled and irradiated ° . Salivary secretion. Decoction of the grain, administered intraperitoneally to mice at a dose of 100 mg/kg, was inactive vs pilocarpine-induced salivary flow in streptozo-tocin-diabetic mice " . ... 

The preparation of protein-rich morama flours follows a number of simple unit operations. These include heating, dehulling, defatting (in some cases), and milling (Fig. 5.5). These operations may impact either... 

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