Quality evaluation and parameter selection of maize by hot-air and vacuum drying

In order to reasonably evaluate the quality of maize after hot air and vacuum drying, the physical, physiological and biochemical quality parameters of maize dried by hot air and vacuum drying methods in different levels of drying strength were determined and analyzed. The quality evaluation parameters of dried maize were selected by using of the principle component analysis method. The results indicated that, to hot air drying, crack ratio was less than 35% when drying temperature was below 60℃, drying rate was lower than 4.21%/h. Drying temperature of maize seed should under 45℃. When drying temperature was above 75℃, drying rate was higher than 4.56%/h, crack ratio increased rapidly, content of MDA and fatty acid value increased, but the activity of POD decreased. The higher the initial moisture of maize had, the larger drying strength influenced on quality parameters. To vacuum drying, crack ratio was less than 35% when drying temperature below 75℃, drying rate lower than 5.56%/h, and the germination rate of maize had a less change under 45℃. When drying temperature was above 75℃, drying rate was higher than 5.56%/h, the activity of POD decreased, MDA, conductivity and fatty acid value increased, but the activity of POD decreased. By using of the principle component analysis method, the sensitive quality evaluation parameters of maize by hot air drying that were crack ratio, fatty acid value, the activity of POD, content of MDA and conductivity, while by vacuum drying were crack ratio, germination rate, activity of POD and conductivity. The comprehensive evaluation mode was erected, and it could fundamentally reflect maize drying quality.