Res. Agr. Eng., 2026, 72(2):142-153 | DOI: 10.17221/149/2025-RAE

Effect of maturity and the colour parameters on the cocoa opening force using the existing mechanical systemOriginal Paper

Randy Amuaku ORCID...1,3, Eric Amoah Asante ORCID...1, Emmanuel Y.H Bobobee ORCID...1, Jerry Oppong Adutwum ORCID...2, Godwin Amanor ORCID...3
1 Department of Agricultural and Biosystems Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
2 Wood Physics and Drying Laboratory, CSIR-Forestry Research Institute, Kumasi, Ghana
3 Department of Mechanical Engineering, Koforidua Technical University, Koforidua, Ghana

The study assessed the mechanical and colorimetric properties of cocoa (Theobroma cacao L.) pods at various maturity stages to improve the mechanised pod-opening efficiency. Thirty pods, each replicated three times, underwent compressive loading and colour analysis using the CIE Lab* colour space to correlate the colour attributes with mechanical resistance. The pod maturity significantly (P < 0.05) influenced the opening force and compressive strength: unripe pods required the highest mean force (1 222 N) and strength (0.316 N.mm–2), while aged pods needed only 346 N and 0.094 N.mm–2. The longitudinal orientation yielded higher and more consistent force  response than the transverse orientation, with the ANOVA confirming significant differences (P < 0.05). The colour parameters, especially yellowness (b*) and hue angle (H°), were strongly and negatively correlated with the mechanical properties (r ≥ –0.99, P ≤ 0.05), making them reliable non-destructive indicators of maturity. The Partial Least Squares Regression (PLSR) models validated the predictive power of the combined colour and mechanical data, with the longitudinal orientation producing the highest model accuracy across all the maturity levels. Combining the colour-based maturity assessment with mechanical testing provides a robust framework for designing automated, maturity-sensitive cocoa pod-opening systems that optimise the efficiency and reduce bean damage during post-harvest handling. The research approach provided an outstanding quantitative assessment.

Keywords: colour space analysis; compressive strength; orientation effects; postharvest mechanisation; ripeness indicators

Received: August 31, 2025; Accepted: February 26, 2026; Prepublished online: June 16, 2026; Published: June 22, 2026  Show citation

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Amuaku R, Amoah Asante E, Y.H Bobobee E, Oppong Adutwum J, Amanor G. Effect of maturity and the colour parameters on the cocoa opening force using the existing mechanical system. Research in Agricultural Engineering. 2026;72(2):142-153. doi: 10.17221/149/2025-RAE.
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