Wheat separation

The first-break roUs of a mill are cormgated rather than smooth like the reduction roUs that reduce the particles of endosperm further along in the process. The rollers are paired and rotate inward against each other and at different speeds. The clearance between rollers and the pressure as well as the speed of each separate roUer, can be adjusted. At each breaking step, the miller selects the milling surface and the cormgations the speed of and interrelation between the rollers depend on the type and condition of the wheat. 

Soft-wheat flours are sold for general family use, as biscuit or cake flours, and for the commercial production of crackers, pretzels, cakes, cookies, and pastry. The protein in soft wheat flour mns from 7 to 10%. There are differences in appearance, texture, and absorption capacity between hard- and soft-wheat flour subjected to the same milling procedures. Hard-wheat flour falls into separate particles if shaken in the hand whereas, soft-wheat flour tends to clump and hold its shape if pressed together. Hard-wheat flour feels slightly coarse and granular when mbbed between the fingers soft-wheat flour feels soft and smooth. Hard-wheat flour absorbs more Hquid than does soft-wheat flour. Consequently, many recipes recommend a variable measure of either flour or Hquid to achieve a desired consistency. 

Fibers and Fiber Sources. Fibers are present ia varyiag amounts ia food iagredients and are also added separately (see Dietary fiber). Some fibers, including beet pulp, apple pomace, citms pulp, wheat bran, com bran, and celluloses are added to improve droppiags (feces) form by providing a matrix that absorbs water. Some calorie-controUed foods iaclude fibers, such as peanut hulls, to provide gastroiatestinal bulk and reduce food iatake. Peanut hulls normally have a high level of aflatoxias. They must be assayed for aflatoxia and levels restricted to prevent food rejection and undesirable effects of mycotoxias. 

The quality of flour used ia the production of yeast-raised products depends on several factors, including the quality and characteristics of the wheat variety, the environmental conditions under which the wheat was grown, the skill of the miller in separating the endosperm of the wheat kernel from the germ and bran, and the proper treatment of the flour in the mill. 

Flour and Feed Meal The roller mill is the traditional machine for grinding wheat and lye into high-grade flour. A typical mill used for this purpose is fitted with two pairs of rolls, capable of making two separate reductions. After each reduction the product is taken to a bolting machine or classifier to separate the fine flour, the coarse produc t being returned for further reduction. Feed is supphed at the top, where a vibratoiy shaker spreads it out in a thin stream across the full width of the rolls. 

Table 5.15 Relative signal responses from various injection volumes for the LC-MS-MS analysis of a wheat forage matrix sample. Reprinted from J. Chromatogr., A, 907, Choi, B. K., Hercules, D. M. and Gusev, A. L, Effect of liquid chromatography separation of complex matrices on liquid chromatography-tandem mass spectrometry signal suppression , 337-342, Copyright (2001), with permission from Elsevier Science...

One practical aspect of the procedure for monitoring carbon flow following C labeling is the need to separate roots from the soil for analysis. Incomplete removal of roots can lead to an overestimation of rhizodeposition, but overzealous washing of soil may lead to leaching of " C or loss of fine roots. This problem has been examined in detail for wheat and barley, and procedures to correct for these errors have been developed (69). 

Even with these problems, attempts have been made to demonstrate that mulches suppress weeds allelopathically. Putnam and DeFrank (12) and Barnes and Putnam (39) used Populus wood shavings to separate chemical and physical effects of mulches. Their work indicated that certain mulches do possess allelopathic potential. Liebl and Worsham (9) and Shilling and Worsham (14) placed mulch on tilled soil, after tilling, in an attempt to provide the weeds with an exposure to light. Their work also indicated that at least part of the suppression of weeds by wheat and rye mulch is allelopathic. Thus, research to date indicates that both mulch and the lack of soil tillage contributes to the suppression of weeds in no-till cropping systems. 

Analytical techniques for the quantitative determination of additives in polymers generally fall into two classes indirect (or destructive) and direct (or nondestructive). Destructive methods require an irreversible alteration to the sample so that the additive can be removed from the plastic material for subsequent detention. This chapter separates the additive wheat from the polymer chaff , and deals with sample preparation techniques for indirect analysis. 

Young, P.M., Wheat, T.E. (1990). Optimization of high-performance liquid chromatographic peptide separations with alternative mobile and stationary phases. J. Chromatogr. 512,273-281. 

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