Chapter 4 - Chemical composition and nutritive value

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The composition of the kernel fractions of sorghum and pearl millet is given in Table 16. The sorghum bran is low in protein and ash and rich in fibre components. The germ fraction in sorghum is rich in ash, protein and oil but very poor in starch. Over 68 percent of the total mineral matter and 75 percent of the oil of the whole kernel is located in the germ fraction. Its contribution to the kernel protein is only 15 percent. Sorghum germ is also rich in B-complex vitamins. Endosperm, the largest part of the kernel, is relatively poor in mineral matter, ash and oil content. It is, however, a major contributor to the kernel's protein (80 percent), starch (94 percent) and B-complex vitamins (50 to 75 percent).

The pearl millet bran is low in mineral matter like that of sorghum, but it is remarkably rich in protein ( 17.1 percent). The germ fraction in pearl millet is relatively large, 16 percent as against 10 percent in sorghum. It is also rich in oil (32 percent), protein ( 19 percent) and ash ( 10.4 percent). Practically all the oil (87 percent) of the whole kernel is in the germ fraction, which also accounts for over 72 percent of the total mineral matter. Greater concentration of minerals in the germ and the bran layers than in endosperm is typical of cereal grains (MacMasters, Hinton and Bradbury, 1971). The total fat content of pearl millet is higher than that of other millets and sorghum because of the size of the germ and its high oil content and because of somewhat higher levels of fat in the bran fraction.

 

Variation in grain composition

Like other cereals, sorghum and millets are predominantly starchy. The protein content is nearly equal among these grains and is comparable to that of wheat and maize (Table 17). Pearl and little millet are higher in fat, while finger millet contains the lowest fat. Barnyard millet has the lowest carbohydrate content and energy value. One of the characteristic features of the grain composition of millets is their high ash content. They are also relatively rich in iron and phosphorus. Finger millet has the highest calcium content among all the foodgrains. High fibre content and poor digestibility of nutrients are other characteristic features of sorghum and millet grains, which severely influence their consumer acceptability. Generally the whole grains are Important sources of B-complex vitamins, which are mainly concentrated in the outer bran layers of the grain.

TABLE 16: Nutrient content of whole kerneI and its fractionsa

Kernel fraction % of
kernel weight
Proteinb
(%)
Ash (%) Oil (%) Starch (%) Calcium (mg/kg) Phosphorus (mg/kg) Niacin (mg/100g) Riboflavin (mg/100 g) Pyridoxin (mg/100g)
Sorghum  
Whole kernel 100 12.3 1.67 3.6 73.8     4.5 0.13 0.47
Endosperm 82.3 12.3 0.37 0.6 82.5     4.4 0.09 0.40
    (80) (20) (13) (94)     (76) (50) (76)
Germ 9.8 18.9 10.4 28.1 13.4     8.1 0.39 0.72
    (15) (69) (76) (20)     (17) (28) (16)
Bran 7 9 6.7 2.0 4.9 34.6     4.4 0.40 0.44
    (4 3) (11) (11) (4)     (7) (22) (8)
Pearl millet  
Whole kernel 100 13.3 1.7 6.3   55 358      
Endosperm 75 10.9 0.32 0.53   17 240      
    (61) (14) (6)   (25) (56)      
Germ 17 24.5 7.2 32.2            
    (31) (71) (87)            
Bran 8 17.1 3.2 5.0   168 442      
    (10) (15) (6)   (36) (15)      

a Values in parentheses represent percentage of whole kernel value.
b N 6.25
Sources: Hubbard. Hall and Earle. 1950 (sorghum): Ahdelrahman. Hoseney and Varriano-Marston, 1984 (pearl millet).

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