Insights into the effects of predrying treatments and temperature on drying kinetics, moisture diffusivity, activation energy and quality attributes of Frafra potato (Solenostemon rotundifolius) slices

Frafra potato ( Solenostemon rotundifolius ) is an underutilized root tuber with significant potential to contribute to food and nutritional security in marginalized communities. However, its utilization is constrained by postharvest challenges such as discoloration and rapid spoilage. This study investigated the effects of predrying treatments and drying temperatures on the drying kinetics, moisture diffusivity, activation energy, and quality attributes of dried S. rotundifolius slices. Four predrying treatments (0.5% potassium metabisulfite solution (KMS), steam blanching, KMS + blanching, control) were evaluated at drying temperatures of 40 –70 °C. Results indicated that drying occurred predominantly in the falling rate period and was influenced by both predrying treatments and drying temperature. The Page model showed the best fit to the drying data, exhibiting R 2 values ranging from 0.9951 to 0.9994. The effective moisture diffusivity ranged from 2.91 × 10 −10 m 2 /s – 8.23 × 10 −10 m 2 /s, while activation energy varied across treatment, reaching 18.27 kJ/mol in KMS-treated samples. KMS pretreatment improved color quality by increasing lightness and whiteness index and reducing browning across all drying temperatures. Drying reduced total phenolics, flavonoids, β-carotene, vitamin C and antioxidant activity, with losses ranging from 27.37%–71.66%, 9.00%–97.70%, 23.51%–89.92%, 18.47%–90.20% and 41.17%–77.37%, respectively. However, KMS-treated samples dried at 40 °C showed the highest β-carotene retention (759.31 µg/100 g d.b.), while blanched samples dried at 60 °C showed the highest vitamin C retention (141.88 mg/100 g d.b). Total antioxidant activity decreased in all dried samples. The findings indicate that quality retention varies among quality attributes, with no single processing condition optimizing all attributes.