Food Chemistry

15.3 Cereals – Milling 709

Table 15.36.Average composition of wheat and rye floursa

A. Wheat flour
Type

405 550 812 1050 1700 b

Flour extraction ratec

40–56% 64–71% 76–79% 82–85% 100%

Starch 82. 381. 878. 177. 869. 2
Protein (N× 5 .8) 11. 712. 313. 012. 912. 7
Lipids 1. 01. 21. 52. 02. 3
Dietary fiberd 4. 75. 05. 66. 013. 4
Minerals (ash) 0. 41 0. 55 0. 81 1. 05 1. 7

B. Rye flour
Type

815 997 1150 1370 1740

Flour extraction ratec

69–72% 75–78% 79–83% 84–87% 90–95%

Starch 74. 873. 571. 371. 168. 6
Protein (N× 5 .8) 7. 28. 03 9. 69. 611. 7
Lipids n.a. 1. 31. 51. 71. 8
Dietary fiberd 7. 610. 19. 310. 516. 2
Minerals (ash) 0. 82 1. 01. 15 1. 37 1. 74

aWeight-% per dry matter of wheat and rye flours. Flour average moisture content is 13 weight-%.
bWhole wheat flour.
cApproximate data.
dIndigestible carbohydrates (water soluble and insoluble), lignin. n.a.: not analyzed.

portion of starch and increases the amount of
kernel-coating constituents such as minerals, vi-
tamins and crude fiber (cf. Tables 15.8 and 15.9).
Comparing products of the same extraction
rate, rye flour contains higher proportions of
both minerals and vitamins than wheat flour
(Fig. 15.23). It should be pointed out that in the
case of some B-vitamins, such as niacin, this
difference is well-balanced by the higher con-
centrations in wheat in comparison to rye kernels
(cf. Table 15.6). Consequently the concentrations
of such vitamins are similar in rye and wheat
flour.
Bread flours are standardized on the basis of their
ash content in Europe and, particularly, Germany.
The type of flour=ash content(weight %)×
1000 corresponds to the extraction grade. Ex-
amples are provided in Table 15.36 for wheat
and rye flours and their chemical composition

is detailed. Protein and starch contents are also

related to flour particle size (cf. Table 15.37).

Because of the variable particle sizes and den-

sities of protein and starch, a flour sample can

be separated by air classification into a fraction

enriched in protein and starch. These are the so-

called special purpose flours.

Table 15.37.Protein content of wheat flours as affected

by flour particle size

Particle size As portion of flour Protein content

(μm) (weight %) (weight %)

0–13 4 19

13–17 8 14

17–22 18 7

22–28 18 5

28–35 9 7

> 35 43 11. 5