Wheat milling extraction rate

Wheat flour contains 1.5-2.5% fipids, depending on milling extraction rate. Part of this lipid is nonstarch lipid. This portion is extracted with a polar solvent, water-saturated butanol, at room temperature. Nonstarch lipid comprises about 75% of the total lipid of flour (Fig. 15.19). The residual lipids (25%) are bound to starch (cf. 15.2.4.1). Nonstarch- and starch-bound lipids in wheat differ in their composition (cf. Table 15.28 and Table 15.32). In nonstarch-bound lipids the major constituents are the triacylglycerides and digalactosyl diacylglycerides, while in starch-bound lipids, the major constituents are lysophosphatides in which the acyl residue is located primarily in position 1. A decrease in amylose content is accompanied by a decrease in the lipid content (Table 15.28). The ratios of nonstarch-bound lipid classes are dependent... 

The commercial product semolina Cgriess ) is made from endosperm cells of hard durum wheats. Semolina keeps its integrity during cooking and is used mostly for pasta production. Since semolina is a milled flour of low extraction rate, it contains few minerals and vitamins. 

Durum wheat is usually milled into a granular product called refined semolina for pasta production (Table 7.5). Semolina is coarser than flour and is classified depending on average particle-size distribution into coarse, middle, or fine semolina. The average extraction rate is in the range of 65%-70%, and particle-size distribution is in the range of -60 to h-100 U.S. mesh. No more than 3% of the particles should pass a No. 100 sieve (Bizzarri and Morelli 1988, Kill and Turnbull 2001). 

I assumed typical extraction rates during milling, that is, a 15% loss for wheat and a 30% loss for rice, and I used average protein contents of 10% and 7%, respectively. 

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