热风和真空干燥玉米的品质评价与指标筛选

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

为了能对热风和真空干燥后玉米的品质作出合理的评价,对在2种干燥方式和强度下处理的玉米样品物理、生理生化指标进行测定与分析,利用主成分分析法,对干燥后玉米的品质评价指标进行筛选。结果表明,对热风干燥,在温度低于60℃、干燥速率小于4.21%/h时,玉米裂纹率低于35%;当温度高于75℃、干燥速率大于4.65%/h时,玉米电导率急剧升高,丙二醛(MDA)含量、脂肪酸值增加,过氧化物酶(POD)活力下降;玉米初始含水率越高,品质指标受干燥强度的影响越大;而对于真空干燥,当温度低于75℃、干燥速率小于5.56%/h时,玉米裂纹率小于35%,温度高于75℃、干燥速率大于5.56%/h时,电导率和MDA含量、脂肪酸值增加,POD活力下降。主成分分析得到热风干燥玉米的关键评价指标为裂纹率、脂肪酸值、POD活力、MDA含量和电导率;真空干燥玉米的关键评价指标为裂纹率、发芽率、POD活力和电导率,所建立的综合评价模型可反映玉米的干燥品质特性。

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.