Impact Damage Threshold of Young Coconut (Cocos nucifera L.)

Basic information on the bruising incidence of young coconut „buko‟ was generated by establishing the threshold values for impact. Young coconut at two levels of maturity: 6--7 months (M1) and 7-8 months (M2) after pollination were subjected to impact at the cheek by actual dropping on two reference impact surfaces (ground and concrete) and by using a pendulum impactor that was locally fabricated. It was found that the drop heights, which bruised 10% of the fruits, were 20 cm and 22.50 cm for M1 and M2 nuts, respectively with reference to ground surface. For concrete, 10% bruising occurred at 5 cm and 7 cm for M1 and M2 nuts, respectively. The study revealed that bruise volume and bruise depth increased with an increase in drop height for both levels of maturity. M1 nuts should never be dropped from heights greater than 38 cm above ground and not higher than 8 cm above concrete to limit depth of bruise below the critical depth of 1.435 cm. Similarly, drop heights for M2 nuts were noted to be lower than 60 cm and 8 cm for ground and concrete, respectively in order to avoid bruise reaching its critical depth of 1.299 cm. Correlation analysis revealed highly significant correlation between bruise volume and bruise depth and coefficient of restitution (e). Increase in e significantly decreased bruise volume and depth. On the other hand, absorbed energy (Eabs) was noted to have highly significant positive correlation with bruise volume and depth. As Eabs increased, bruise volume and depth also increased. Prediction models were developed and validated relating magnitude of bruise to different parameters in the study.