Drying of high-moisture corn : changes in properties and physical quality

Corn at 30% moisture was air-dried at 25-100 degree C. Drying times to 12% final moisture ranged from 1 hr at 100 degree C to 38 hr at 25 degree C. Chemical composition was unchanged by drying temperature. Increasing drying temperature decreased test weight, germination, nitrogen solubility index, and it increased kernel breakage susceptibility and percentage of floating kernels. Because breakage susceptibility, but not stress-cracking, increased upon high-temperature drying, some chemical or physical change other than stress-cracking in the kernel cell-wall matrix or in the starch granules may have affected breakage susceptibility. Isoelectric focusing showed decreasing protein bands at pi 4.0-6.6 as corn-drying temperature increased from 70 to 100 degree C. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that proteins with molecular weights of 21,000-97,000 decreased after treatment at 70 degree C; they cannot be observed in corn dried at 85-100 degree C. Prolamin levels also decreased as air-drying temperature increased. Thus, corn density, breakage susceptibility, and germination may change upon drying because of changes in albumins and prolamins. These relationships may provide new or improved methods for identifying grain that is damaged or of lower quality due to high-temperature drying.