Effect of vacuum drying and pulsed vacuum drying on drying kinetics and quality of bitter orange (Citrus aurantium L.) slices

The effect of vacuum pressure (20.0, 17.5, 15.0, 12.5, and 10.0 kPa) of vacuum drying (VD) and vacuum pressure (20.0, 15.0, and 10.0 kPa), drying temperature (65, 70, and 75 °C), and the ratio of pulsed vacuum (5:10, 5:15 and 5 min:20 min) of pulsed vacuum drying (PVD) on drying kinetics and quality (rehydration rate and color difference L^*, a^*, b^*, ΔE, and BI) of bitter orange slices (4 mm) were investigated experimentally. Drying bitter orange slices by PVD can effectively increase the drying rate and decrease quality degradation. The optimal condition was 75 °C, 10.0 kPa and 5 min:15 min, which decreased 47.6%, 28.3%, and 15.5% of the moisture ratio, ΔE and BI than VD. Compared with APD, the moisture content undergoing PVD for 4 hr decreased 72.9%. The Third-degree polynomial drying model was the most suitable (R² of 0.99865) for PVD. Novelty impact statement: Drying bitter orange slices by pulsed vacuum drying can effectively increase the drying rate and decrease quality degradation, and the optimal operating condition is 75 °C, 10.0 kPa and the ratio of pulsed vacuum of 5 min:15 min. The optional vacuum drying condition for bitter oranges slices (4 mm) is 75 °C, 15 kPa but not 10kPa. The Third-degree polynomial drying model is the most suitable for pulsed vacuum drying.