Food Chemistry

15.2 Individual Constituents 675

Table 15.6.Chemical composition of cereals (average values)

Wheat Rye Corn Barley Oats Rice Millet

weight %

Moisture 13. 213. 712. 511. 713. 013. 112. 1
Protein (N× 6 .25) 11. 79. 59. 210. 612. 67. 410. 6
Lipids 2. 21. 73. 82. 17. 12. 4 a 4. 05
Available carbohydrates 59. 660. 764. 263. 355. 774. 168. 8
Fiber 13. 313. 29. 79. 89. 72. 23. 8
Minerals 1. 51. 91. 30 2. 25 2. 85 1. 21. 6
mg/kg

Thiamine 5. 54. 44. 65. 77. 03. 44. 6
Niacin 63. 615. 026. 664. 517. 854. 148. 4
Riboflavin 1. 31. 81. 32. 21. 80. 55 1. 5
Pantothenic acid 13. 67. 75. 97. 314. 57. 012. 5

aPolished rice: 0.8%.

Table 15.7.Fractions of various cereals separated by
milling (average weight-%)

Cereal variety Husk Bran Germ Endosperm

Wheat 0 15. 02. 083. 0
Corn 0 7. 211. 081. 8
Oats 20 8. 02. 070. 0
Rice 20 8. 02. 070. 0
Millet 0 7. 99. 882. 3

15.2.1.2 A Review of the Osborne Fractions
of Cereals

In 1907 Osborne separated wheat proteins,
on the basis of their solubility, into four frac-
tions. Sequential extraction of a flour sample

Table 15.8.Chemical composition of anatomical parts of a wheat kernel (average weight-% on dry weight basis)

Ash Crude protein Lipids Crude fibera Cellulose Pentosans Starch

(N× 6 .25)

Longitudinal cells 1. 33. 91. 027. 732. 150 .1–

Cross- and tube cells 10. 610. 70. 520. 722. 938 .9–

Fruit and seed coatings 3. 46. 90. 823. 927. 046 .6–

Aleurone cellsb 10. 931. 79. 16. 65. 328 .3–

Germb 5. 834. 027. 62 .4–––

Starchy endosperm 0. 612. 61. 60. 30. 33. 380. 4

aCrude fiber includes parts of cellulose and pentosans.
bData for carbohydrates are incomplete.

yielded: water-soluble albumins, salt-soluble

(e. g., 0.4mol/l NaCl) globulins, and 70%

aqueous ethanol-soluble prolamins. The glutelins

remained in the flour residue. They can be

separated into two sub-fractions. For this pur-

pose, all the proteins remaining in the residue

are first dissolved in 50% aqueous 1-propanol

at 60◦C with reduction of the disulfide bonds,

e. g., with dithioerythritol. The high-molecular

(HMW) subunits (cf. 15.2.1.3.1) precipitate out

on increasing the propanol concentration to 60%,

while the low-molecular (LMW) subunits

(cf. 15.2.1.3.3) remain in solution.

Further separation of theOsbornefractions and

subfractions into the components is possible

analytically with electrophoretic methods (cf.

Fig. 15.3, 15.4) and analytically and preparatively

with RP-HPLC (cf. Figs. 15.5–15.8).