Bruise susceptibilities of Golden Delicious apples as affected by mechanical impact and fruit properties

In order to reduce bruising damage to fruits, it is necessary to know the effect of fruit properties on bruise susceptibility. Statistical bruise estimation models were constructed to determine the level of bruising in Golden Delicious apples. The regression models were built based upon peak contact force (PF) and impact energy as the main independent variables, with other parameters including fruit curvature radius, temperature and acoustic stiffness (a measure of texture/firmness of fruit and vegetables). Significant effects of acoustic stiffness, temperature and curvature radius and some interactions on bruising were obtained with determination coefficients of 0·87 and 0·93 for the force and energy models, respectively. It was demonstrated that increasing the temperature and lowering acoustic stiffness reduced bruise damage to the fruit. Golden delicious apples with a low radius of curvature developed more bruise damage compared to large apples when impacts were low, but the opposite was true for high impacts, with less damage for small fruit. No significant differences were observed between the predicted bruise volumes of models that included PF and impact energy at all impact levels.