Effective moisture diffusivity, colour and consumer acceptability of marula (Sclerocarya birrea) fruit leather as affected by drying hot air temperature and added sugar

Drying was used as a new approach of preserving marula (Sclerocarya birrea) fruit. The effect of forced convection drying hot-air temperature (50, 60, 70°C) and added sugar (0, 5, 10% w/w) on the moisture diffusivity, colour and consumer acceptability of marula fruit leathers was studied. Moisture diffusivity (5.45×10^‑8 - 1.28×10^‑7 m² s^‑1) and activation energy (20.7-31.7 kJ mol^‑1) increased with hot air temperature and sugar content. Browning (-59.1-694.9) and yellowness indices (60.4-68.1) significantly (p≤0.05) increased with drying temperature and decreased with added sugar content. The sugar content influenced the organoleptic texture, overall consumer acceptability and willingness-to-buy while temperature was negatively correlated with all parameters. The presented research provides a basis for marula fruit leather processing and further research into dried marula fruit products.