Different sieving methods for determining the physical characteristics in ground corn

ABSTRACT. We evaluated various sieving methods to estimate particle size (PS) and geometric standard deviation (GSD) of ground corn. The corn had been previously divided in six fractions and each one ground in a hammermill (1-, 2-, 3-, 4-, 5- or 12-mm sieves). The stacked sieving method, with prior drying at 105ºC without agitators was the reference. We evaluated eight sieving methods, distributed in a factorial design (2 x 2 x 2 x 6), consisting of the following treatments: i) with and without agitators (two 25-mm rubber spheres), ii) with and without previous drying, iii) with a nest of test sieves set in a stacked or reverse, and iv) employing six ground corn degrees, totaling 48 treatments (four replicates). There was a linear increase in PS estimation for methods without drying and stacking and quadratic increases for the others. Reverse, drying, and agitator methodologies gave better sieving of corn, and consequently gave the lowest PS and highest GSD. The results were more pronounced for high-intensity grinding (hammermill sieve with small apertures) in which the differences between the reference method with the drying and reverse methods were up to 210 µm. Reverse sieving combined with agitators allowed the greatest passage of corn particles through the test sieves and promoted better characterization of ground corn.

摘要：本研究评估了多种筛分方法，用于估算粉碎玉米的粒径（Particle Size，PS）与几何标准偏差（Geometric Standard Deviation，GSD）。实验用玉米此前已被分为6个组分，各组分分别在配备1mm、2mm、3mm、4mm、5mm或12mm筛孔的锤式粉碎机中进行粉碎。以先经105℃预干燥且不使用搅拌器的堆叠筛分法作为参照方法。本研究共评估8种筛分方法，采用2×2×2×6析因设计，处理组设置如下：① 是否使用搅拌器（采用2个25mm橡胶球作为搅拌介质）；② 是否进行预干燥；③ 标准筛组采用正向堆叠或反向放置；④ 6种玉米粉碎程度，共计48组处理（每组设置4次重复）。结果显示，未进行干燥且采用正向堆叠的筛分方法，其粒径估算值呈线性增长，其余方法的粒径估算值则呈二次增长。反向放置筛分、预干燥及使用搅拌器的筛分方法对玉米颗粒的筛分效果更佳，最终得到的粒径更小、几何标准偏差更高。该差异在使用小筛孔锤式粉碎机进行的高强度粉碎样品中更为显著，此时参照方法与预干燥、反向筛分方法的粒径差值最高可达210μm。反向筛分结合搅拌器可使玉米颗粒更顺畅地通过标准筛，从而实现对粉碎玉米更精准的表征。