Fresh red chilli (Capsicum frutescens L.) was dried using microwave-vacuum drying (MVD) and the far-infrared radiation assisted microwave-vacuum drying (FIR-MVD) method. The MVD was operated using the microwave power of 100, 200 and 300 W under absolute pressure of 21.33, 28.00 and 34.66 kPa. In terms of FIR-MVD, far-infrared power was applied at 100, 200 and 300 W. The effect of drying conditions, i.e., microwave power, absolute pressure and FIR power, on drying characteristics and qualities of dried product were investigated. It was observed that an increase in microwave power and FIR power with a decrease in absolute pressure could accelerate the drying rate. It was also found that FIR-MVD method required shorter drying time than MVD. Moreover, qualities, i.e., color changes, texture, rehydration ability and shrinkage, of FIR-MVD chilli were found to be better than those of MVD. Consequently, the optimum drying condition of FIR-MVD within this study was microwave power of 300 W under absolute pressure of 21.33 kPa with FIR power of 300 W.
A combination of room cooling and the use of thermal insulation materials to maintain okra quality under simulated storage and transportation was evaluated. Okra pods were packed in plastic baskets and either cooled at 18 °C or not cooled in a room for 2 h. After either room cooling or no cooling, the okra pods were covered with three different materials: (1) perforated linear low-density polyethylene (P-LLDPE), (2) two layers of heat-reflective sheet with thin nonwoven (HRS+TNNW), and (3) metalized foam sheet (MFS). Typical handling (TP) without cooling and covering with P-LLDPE was used as the control. The six treatments were conducted during simulated storage (18 °C for 48 h) and transportation (30 °C for 15 h). Results showed that MFS gave the best insulation properties (Qx and R-values), followed by HRS and TNNW. After room cooling, both HRS+TNNW and MFS materials delayed the time for pulp temperature to reach 18 °C (10 h), compared to P-LLDPE (2 h). TP presented the highest mass loss (17.8%) throughout simulated conditions, followed by cooling plus P-LLDPE (15.2%) and either of the thermal insulation materials with or without room cooling (3.6% to 5.2%), respectively. TP, cooling plus P-LLDPE, and no cooling plus MFS (44% to 56%) showed the highest percentage of decay, while cooling combined with both HRS+TNNW and MFS gave the lowest decay incidence (11–21%). Findings demonstrated that room cooling combined with HRS+TNNW had the highest efficiency for preserving cool temperature and reducing decay, compared to TP and room cooling plus MFS.
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