The optimization of pink guava was executed using central composite face-centred design to optimize the spray drying parameters of inlet temperature, maltodextrin concentration (MDC) and feed flow (FF). The experimental results were significantly (<0.01) fitted into second-order polynomial models to describe and predict the response quality in terms of the final moisture, particle size and lycopene with of 0.9749, 0.9616, and 0.9505, respectively. The final moisture content significantly (<0.01) decreased with increasing inlet temperature and MDC, whereas the particle size increased. In contrast, the lycopene content significantly (<0.01) decreased with the higher temperature and increased with increasing MDC. However, according to multiple response optimization, the optimum conditions of 150°C inlet temperature, 17.12% (w/v) MDC and 350 mL/h FF-predicted 3.10% moisture content, 11.23 μm particle size and 58.71 mg/100 g lycopene content. The experimental observation satisfied the predicted model within the acceptable range of the responses.

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The performances of industrial dryers, namely the inclined bed dryer (IBD) and the fluidized bed dryer (FBD) combined with IBD, in terms of drying kinetics, energy consumption, and quality of paddy were investigated in this study. Drying parameters used in a single-stage paddy drying using IBD and a two-stage drying using FBD combined with IBD were analyzed to assess the existing performances of the drying techniques. The overall performances of the current drying practices exhibited inconsistent results with the operating parameters, such as drying air temperature, drying time, and air flow rate among the drying process lines. Distinct variations in moisture reduction and energy consumption of the drying systems were identified. Poor performance of the industrial fluidized bed dryer was observed in the case of drying in low capacity that caused higher specific energy consumption. However, the quality of milled rice obtained from both drying systems was found to be almost similar. Minimal process time (i.e., up to 24.5% less) was found in the paddy dried with FBD as the first-stage drying, followed by IBD as the second-stage drying.