BULK-DENSITY AND RESISTANCE TO AIR-FLOW OF SLICED ONIONS

The bulk density of sliced onions (Allium cepa L., cv. Southport White Globe) at different moisture contents and slice thicknesses was deter mined by weighing the contents of a cylindrical container of known vol ume. The void fraction of the samples was estimated from its relations hip with apparent and bulk densities. The bulk density and void fracti on of onion slices varied non-linearly with moisture content and linea l ly with slice thickness. For dried onion flakes, the bulk density an d void fraction varied non-linearly with slice thickness and moisture content. The experimental results on bulk density and void fraction of onion slices and of dried onion flakes were best explained by second order polynomial models. Using a laboratory apparatus, the resistance to airflow though a bed of the sliced onions of 5 mm initial thickness were measured experimentally and the results at different moisture co ntents were described well by the modified Ergun equation.