The influence of inlet and exit air temperatures (160-200 and 80-100 C, respectively) on the spray drying of mandarin oil was evaluated by using a three-level factor design. For optimization, dryer evaporative rate, volatile oil retention, and microencapsulation efficiency were considered as response variables. The response surface analysis produced significant (p < 0.05) polynomial regression equations that were successfully fitted for all response variables and no significant (p > 0.05) lack of fit was indicated for the reduced models. This observation confirmed an accurate fitness of the reduced response surface models to the experimental data. The multiple response optimizations indicated that an inlet air temperature of 200 C and an exit air temperature of 80 C were predicted to provide the maximum evaporative rate, volatile oil retention, and microencapsulation efficiency in the studied ranges.

Summary The influence of inlet and outlet air temperatures (180–220 and 80–100 °C, respectively) on the spray drying of lime essential oil was evaluated by using a three‐level factor design. For optimisation, dryer evaporative rate, volatile oil retention, and microencapsulation efficiency were considered as response variables. The response surface analysis produced significant (P < 0.05) polynomial regression equations that were successfully fitted for all response variables, and no significant (P > 0.05) lack of fit was indicated for the reduced models, with the exception of microencapsulation efficiency. This observation confirmed an accurate fitness of the reduced response surface models to the experimental data. The multiple response optimisations indicated that an inlet air temperature of 220 °C and an outlet air temperature of 85 °C were predicted to provide the maximum evaporative rate (7.7 kg h−1), volatile oil retention (95.7%), and microencapsulation efficiency (99.9%) in the studied ranges. Checking of the optimisation showed that with these optimal parameters, a very good closeness between the experimental and predicted values was obtained.

Response surface methodology was used to optimize the spray-drying process for the development of stingless bee honey powder. The independent variables were: inlet air temperature (110–150 oC) and maltodextrin 10DE content (50–70 % wb). The responses were powder yield, moisture, volatiles retention, solubility time, hygroscopicity, bulk loose, and hydroxymethylfurfural content. Powder moisture content, solubility time, hygroscopicity and loose bulk density were negatively affected by inlet air temperature, while powder yield, volatiles retention and hydroxymethylfurfural content were directly related. Powder yield, volatiles retention and solubility time increased with the rise in maltodextrin content, while moisture content, hygroscopicity, loose bulk density and hydroxymethylfurfural content were negatively affected by maltodextrin content. Multiple response optimization indicated that an inlet air temperature of 150 oC and maltodextrin content of 61 % wb were predicted to provide 40 % powder yield, 4.9 % wb moisture content, 71 % volatiles retention, 242 s solubility time and 232 mg/kg hydroxymethylfurfural content.

Response surface methodology was used to optimize spray-drying process for concentrated orange juice. Independent variables were: inlet air temperature (130-170 ºC) and maltodextrin 12DE content (60-75% wet basis (wb)). Responses variables were powder yield, moisture, and ascorbic acid retention. Moisture content was negatively affected by inlet air temperature, while ascorbic acid retention was directly related. Powder yield and ascorbic acid retention increased with the rise in maltodextrin content, while moisture content was negatively affected by maltodextrin content. Multiple response optimisation indicated that an inlet air temperature of 155 ºC and maltodextrin content of 74% wb were predicted to provide 77% powder yield, 3.7% wb moisture content, and 89% ascorbic acid retention.

In this study, production of sour orange juice powder utilizing a spray dryer was investigated. To prevent stickiness, maltodextrin DE 12 was used as a drying agent. While feed fl ow rate, feed temperature, and air fl ow rate were kept constant, inlet air temperature (120-160 °C) and maltodextrin content (maltodextrin dry solids/100 g feed mixture dry solids; 10-20%, w/w) were selected as the independent variables. Product properties investigated included ascorbic acid, volatile compounds, and moisture content. Ascorbic acid retention, volatiles retention, and moisture content were used in optimization of the process by response surface methodology. The optimum inlet air temperature and maltodextrin content were 156 °C and 20% w/w maltodextrin, respectively. This study revealed that by applying these optimal conditions, sour orange juice powder with 81.5% ascorbic acid retention, 5.5%, w/w moisture content, and 78% volatiles retention was produced.