Physical and mechanical properties of peanut kernel from four cultivars grown in Ecuador

Equipment mismatch is a common challenge during postharvest processing of peanuts in developing regions due to limited engineering data. This study determined the physical and mechanical properties of four peanut cultivars (Rosita, Charapotó, Barriga de Sapo and Caramelo) grown in Manabí, Ecuador, to provide parameters for design and optimization of postharvest equipment. Kernel length equatorial diameter, mass, true density, bulk density, roundness coefficient, flowability (angle of repose), friction coefficients and rolling resistance coefficients (rubber, stainless steel, carbon steel) were measured using standardized procedures on rubber, stainless steel, and carbon steel surfaces. 90.5% of kernels had a diameter within the 6.8–10.28 mm suitable for mechanical sizing; however, gravimetric or densimetric methods are recommended for accurate classification. The measured angle of repose (28–31°) indicates excellent flowability of peanut kernels. Rubber surfaces showed the highest static (μs=1.10±0.01) and dynamic (μd=0.95±0.01) friction and rolling resistance, whereas stainless steel showed the lowest (rubber > steel). The resulting dataset supports material selection (e.g., stainless steel to reduce energy demand), density-based quality control, and DEM/CFD inputs for adapted seeders, conveyors, and storage systems. Measured ranges are consistent with values reported for cultivars from Asia, Africa, and the Mediterranean, while highlighting regional differences relevant to equipment design.