Thin-layer drying kinetics and quality assessment of octopus (Octopus sp.) using mixed and open solar dryers

Octopus (Octopus sp.) is highly perishable marine species for which efficient drying is essential to extend shelf life in tropical climates. The anatomical heterogeneity of the octopus complicates consistent drying. This study systematically evaluated the performance of a mixed solar dryer (MSD) and open solar drying (OSD) across distinct anatomical regions (head, mantle, and tentacles), with emphasis on drying kinetics and quality attributes. Five thin-layer models were applied to characterize moisture reduction, and product quality was assessed by measuring browning, protein, fat, and ash content. The MSD achieved a 20% higher temperature and 29% lower humidity, resulting in a 74% increase in drying rate relative to OSD. The Hasibuan and Daud model exhibited the highest predictive accuracy (coefficient of determination (R2) = 0.9965; root mean square error (RMSE) = 0.0168; sum of squared errors (SSE) = 0.0058). Significant interaction effects between anatomical region and drying method were observed for browning and ash content (P < 0.05), whereas protein and fat content were primarily influenced by anatomical characteristics. Overall, the MSD produced products with reduced browning and enhanced nutrient retention. These results support the implementation of MSD technology by small-scale processors to improve both drying efficiency and product quality in octopus preservation.