Effects of Germination of Wheat, Oats, and Pearl Millet on Alpha‐Amylase Activity and Starch Degradation

Hard red winter wheat, oats, and pearl millet were germinated at 15°C for periods up to 14 days. Endosperm areas in kernels fractured with a razor blade and starches isolated from the malted flours were examined with a scanning electron microscope to determine the morphology of starch granules and the nature of α‐amylolytic attack on granules. Free sugars content, damaged starch content, and α‐amylase activity of the flours were determined to establish relationships between physical changes in the cereal grains and formation of α‐amylase during germination. Starch granules in the three cereals were degraded during germination by α‐amylase accompanied by production of free sugars and increases in the damaged starch of flours milled from the germinated grains. The cementing material embedding starch granules in endosperms of wheat and oats decreased and disappeared during germination; these changes were not obvious in germinated millet endosperm. Amorphous‐appearing material seemed to cover starch granules in the endosperm of wheat and oats during later stages of germination, but were not observed in the isolated starch granules. Although wheat starch granules had the highest α‐amylase activity, this enzymic degradation was less than expected. Enzymic attack was evidenced as channels or pits on the surfaces of wheat and millet starch granules. Compound oat starch granules were relatively resistant to enzymic attack and no evidence of erosion of the granule surface was observed; small granula were released from the compound granules during germination. The most extensive degradation was obtained with millet starch, appearing as discrete holes leading to the interior of the granule. Concentric shells were visible in the interior of wheat and millet starch granules, but were not observed in oat starch granules.