Modeling Static Bruising in Apple Fruits: A Comparative Study, Part I: Analytical Approach

ABSTRACT- Bruising degrades the quality of fresh apple fruits. Reducing bruise damage is of utmost importance in designing and developing processing equipments. The main objective of the present study was to introduce an analytical method to predict the allowable static load applicable to apple fruits. To predict the strain energy absorbed by the fruit, a point load was applied on the solid spherical object. The strain energy of the spherical element was extended to the whole body using a triple integral in the spherical domain. In order to verify the results, a series of compression tests were carried out using a universal testing machine on an apple kept at two different storage and initial fruit temperatures (zero and 25oC). The results showed a strong polynomial relation with a coefficient of determination of 0.990 between the value of the theoretical stored strain energy and the experimental one. Also, it was found that the size of the bruised area can be determined by its corresponding theoretical stored strain energy with an error less than 3.6 percent.