Raisin Production by Convective–Microwave Dryer and Optimization of Ochratoxin A Content, Physicochemical, Sensory Characteristics, and Fungal Load of Raisin

Raisins are so popular in the human diet as a nutritional and sweet snack. The quality of this foodstuff depends on drying conditions. To minimize ochratoxin A (OTA) content and yeast and mold content (YMC) in raisins with favorable physicochemical and sensory properties, the response surface methodology (RSM) and the face-centered central composite design (FCCD) were utilized. The independent variables were studied over a range of microwave power (0-220 W) and temperature air (35°C-55°C). The microwave power had a significant effect on the OTA value and YMC of dried samples. The use of microwaves in drying contributed to a higher decline in OTA content and YMC than in conventionally dried samples. The regression models detected for OTA content, acidity, pH, rehydration ratio (RR), water holding capacity (WHC), shrinkage, appearance, texture, acceptability, and YMC were significant and reliable. The desirability function was applied to recognize an optimized situation. The result of the RSM analysis showed the optimum conditions for obtaining healthy raisins with desired physicochemical and sensory attributes by microwave-convective dryer at 220 W microwave power and 38.68°C air temperature.