Development of a Frequency-based Firmness Index for Solid Fruits and Vegetables of Ellipsoidal Shape

Firmness is an important biomaterial property in assessing the internal quality of agricultural products. This article briefly summarizes recent research results of a new frequency-based firmness index for solid fruits and vegetables of ellipsoidal shape. This new firmness index is in fact a generalization of the conventional ones targeted for spherical fruits and vegetables. Meanwhile, it can also serve as a dynamic Modulus of Elasticity (MOE) estimator. The development of this new firmness index extends the potential applications of non-destructive firmness estimation to non-spherical fruits and vegetables. The theory of formulation is first introduced, followed by a discussion on two experimental case studies, “tri-star” pear and Chinese radish. The results show that the new firmness index is indeed more robust and accurate, especially for ellipsoids with long principal axes ratios.