Developing an appropriate system for onion grading

Onion (Allium cepa,L)is a crop of warm climate and it is grown worldwide. Manual grading of onion is a labor-consuming and tedious operation coming with many losses. Sizing is one of the most important operations affecting onion export. It determines the weight of standard sale package and simplifies the mechanization of different handling systems. Sizing also has an effect on heat transfer processes, since size-graded produce allows heat transfer uniformity during drying, cooling and freezing processes.The aim of this work was to develop an appropriate machine for sizing onions, reduce losses and reduce grading costs. Maximum sizing efficiency obtained was 94.9% at zero longitudinal angle and at a belt speed of (0.23 m/s), while it was 94.5% at 10o longitudinal angle for the same belt speed. The overall average of the sizing efficiency (94.33%) was recorded at 20o side angle and the highest grading capacity (1.72 t/h) was obtained at 10o side angle and 10o longitudinal angle. Total costs of grading the produce were 3.89 LE/t.(0.7 US$/t). This machine has the potential to size other crops like potatoes, tomatoes, apples and citrus fruits.