Ripeness Inspection of Oil Palm Fruits by Applying Hardness Test Technique

Abstract

The objective of this study was to investigate whether the ripeness of oil palm fruits could be estimated based on their hardness. The hardness was examined by indenting with a steel ball on the exocarp of the fruit with the required indentation force (kgf) measured. Five steel balls with diameters of 4, 6, 8, 10, and 12 mm were tested on CIRAD and COMPACT varieties of oil palm, with the fruits in unripe, under-ripe, and ripe stages. The results reveal that, on using five ball indenters, the average hardness of unripe oil palm fruit differs from those of under-ripe and ripe fruit, on both CIRAD and COMPACT varieties. In contrast, the average hardness of under-ripe and ripe stages did not differ, while the hardness in three stages oil palm fruits reflects the oil and moisture percentages. Oil percentages in the COMPACT oil palm fruit in unripe, under-ripe, and ripe stages were 27.71%, 75.11%, and 76.78%, respectively, and for CIRAD variety of oil palm these were 59.42%, 76.67%, and 75.79%, respectively. The empirical dependence of hardness on oil content was y=1.47x2+11.20x+55.36 for the COMPACT oil palm and y=-1.90x2+3.21x+77.49 for the CIRAD oil palm.