Effect of pretreatment and drying method on drying kinetics of ackee (blighia sapida) arils

Abstract

The research investigated the effect of different pretreatments and different drying methods on the drying kinetics of ackee arils (AA). Freshly harvested AA were portioned and subjected to pretreatments, including blanching at 85 °C for 3 min, dipping in salt (NaCl) solutions of 1, 2, and 3% w/v for 5 min, and untreated samples served as the control. The aril samples were dried at different temperatures (50, 60, and 70 °C) and monitored at intervals until a constant weight was achieved. They were subsequently analyzed for drying kinetics, effective moisture diffusivity (Deff), and activation energy (Ea), using standard methods. The moisture content reduced from 62.9 to 3% and was in a falling rate period. The moisture loss occurred at a faster rate in AA dried at 70 °C compared to 60 °C and 50 °C. The Deffincreased with an increase in drying temperature from 50 to 70 °C. The overall highest Deffwas 2.07 ×10-4m2/s at an oven drying temperature of 60 °C, with 1% salt solution pretreatment, while the lowest was 4.23 × 10-6m2/s at an oven drying temperature of 70 °C, 3% salt solution pretreatment. The Ea obtained falls within the range of (106.10 –125.29 kJmol-1), which indicates that the AA processed is highly sensitive to temperature. The obtained drying data were fitted into five different thin-layer drying mathematical models using the coefficient of determination (R2), least values of Chi-Square (χ2), Root Mean Square Error (RMSE) and Mean Biased Error (MBE). Pretreatment had a significant effect (p≤0.05) on the drying of AA. The Midilli and Kucuk model described the drying behaviour of AA pretreated with 1% salt (NaCl) solution and oven-dried at 70 °C satisfactorily with the R2 values of 0.999