Food Structure


Factors responsible for grain hardness in sorghum are not well understood. Therefore, a study was undertaken to observe differences in the developmental processes of three sorghum varieties which vary in endosperm texture: hard, intermediate, and soft. Grain samples were collected at 5 day intervals beginning at 5 days after half-bloom (DAHB) until physiological maturity (40 DAHB) and prepared for viewing with scanning electron microscopy and transmission electron microscopy.

Comparisons were made between vitreous and floury endosperm portions of each variety and among the three varieties. The major difference between vitreous and floury endosperm was the degree to which the protein matrix was present and continuous. The protein matrix which surrounds the starch granules forms at approximately 20 DAHB. The proportion of cells in the endosperm with a continuous protein matrix corresponds to the proportion of vitreous endosperm in the mature kernel. A similar sequence of development was observed in the hard, intermediate, and soft varieties. however, the harder varieties appeared to develop faster than the softer varieties. Differences between hard and soft varieties were visible as early as 15 DAHB. In the early stages of endosperm development, the hard variety had a higher concentration of protein bodies in the outer endosperm than the softer varieties.

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