Electrical density sorting and estimation of soluble solids content of watermelon

The relationship between density and internal quality of watermelon was investigated. The density of watermelon was found to be related both to the degree of hollowness and the soluble solids content which can be used as a measure of sweetness. The soluble solids content of watermelons can be estimated from density and mass by multiple regression analysis. An optimum range of density was found which provides an indication of watermelon quality. A new electrical method is proposed for density sorting of spherical fruits, which measures the volume by electric capacity and mass by electronic balance. A new automatic density sorting system was developed for measuring the degree of hollowness, which enables low density watermelons with cavities or deteriorated porous flesh to be removed and permits the soluble solids content of watermelons to be estimated. The system was tested with satisfactory results. (C) 1997 Silsoe Research Institute.