Development and evaluation of a mechanical model for the assessment of cocoa pod opening force

Abstract

Confronted with limited data on cocoa pod opening force and bean separation for optimization, several machines developed have faced challenges over the years. To address this challenge, a mechanical model for the pod opening force assessment was developed and evaluated using Forastero, Amezonia, and Amelonado cocoa cultivars under 0, 2, 4, 6, and 8-day post-harvest delay. Ten Forastero pods were fixed one after the other between two parallel plates on the developed model on the first day of harvest. The pressure shaft was turned through a number of revolutions and the corresponding opening force was recorded using a sensor placed underneath the bottom plate for five pods under longitudinal and lateral orientations and repeated for the other postharvest delays. The process was replicated five times using Amezonia and Amelonado cultivars. Results showed that the opening force decreases with increasing postharvest delay. Terminal opening force for the Forastero >Amezonia >Amelonado. ANOVA showed no significant difference (P ˃ 0.05) between successive postharvest delays for the Forastero, except 4-6 days (P > 0.05) for Amelonado, and 6-8 days (P < 0.05) for Amezonia. Therefore, the maximum postharvest delay for effective pod opening is 4 days for Amelonado, 6 days for Amezonia and 8 days for Forastero. The quantitative assessment of the PLSR model for the Forastero cultivar (R² = 0.70309; RMSE = 0.01404) is considerably better than the Amezonia cultivar (R² = 0.68875; RMSE = 0.02134) and Amelonado cultivar (R² = 0.62312; RMSE = 0.01785). The technique highlighted the cultivar differences and provided excellent quantitative analysis.