The Impacts of Different Oven-Drying Temperatures on the Elemental Profile and Microstructural Integrity of black bean(Akidi) Seeds

Abstract

This study examined how oven-drying temperature affects the mineral content and physical structure of black beans (Akidi), a protein-rich legume vital to sub-Saharan African diets. Fresh cowpea seeds were dried at 45, 50, 55, 60, and 65°C in a forced-air oven. Freeze-dried seeds served as the control. Mineral analysis was conducted using energy-dispersive X-ray spectroscopy, and structural changes were observed with scanning electron microscopy. Results showed significant temperature effects. Carbon and oxygen levels decreased with rising temperatures, dropping from 63.5% to 49.8% and 26.4% to 20.4% respectively, due to moisture loss and organic compound volatilization. Conversely, mineral concentrations increased substantially — potassium rose from 3.2% in fresh seeds to 10.5% at 65°C. Sulphur followed a non-linear pattern, indicating thermal degradation at higher temperatures. Structural examination revealed progressive seed coat deterioration. Minor wrinkling appeared at 45°C, micro-cracks formed at 50°C, crack networks developed at 55–60°C, and complete structural collapse with mineral aggregation occurred at 65°C. The findings indicate that moderate drying temperatures between 50–55°C offer the optimal balance. This range achieves meaningful mineral concentration while maintaining seed coat integrity essential for storage and processing. These results provide scientific guidance for improving post-harvest handling of cowpeas, supporting better nutritional security through optimized preservation protocols.

Keywords

• Black bean
• Oven-drying temperature
• Scanning electron microscopy
• Mineral composition
• Seed coat integrity
• Microstructure

Supporting Institution

Tertiary Education Trust Fund (TetFund) Nigeria

Ethical Statement

This article does not require any Ethical Committee Decision.

Thanks

Our appreciation goes to Tertiary Education Trust Fund (TETFund) of Nigeria that funded this research.

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