Comparing the effect of osmotic, hot air oven and microwave methods of drying on physicochemical and sensory properties of strawberry

n this study, the effect of different drying methods was investigated on physicochemical characteristics, sensory properties and nutritional quality of strawberry and effective factors on the increasing of its shelf life. For osmotic dehydration treatment, temperature (35 and 45 °C), mixture of fructose and sucrose syrup concentration (70%(W/V) (20% fructose 50% sucrose)), calcium chloride (0.75 and 1.5% (W/V)), during 5 hours with 1 to 8 ratio of fruit to osmotic solution was used. The best treatment among the 8 different treatments was the treatment 8 (osmotic solution containing %50 fructose with %20 sucrose %1.5 calcium chloride and treatment time of 5 hours at 45°C) with respect to the lowest SG/WL which lead to better drying of strawberries in comparison with the other treatments and was known as the best treatment. Then, the best osmotic treatment with respect to physicochemical characteristics, and sensory properties was evaluated and compared to dried strawberry samples by microwave, hot air oven and control sample. The results showed the moisture content (%28, %37 and %18), pH (3.57, 3.15 and 3.19), acidity (% 0.042, %0.045 and % 0.044), Brix (%23, %15 and %26), total sugar (%15, %4 and %3), vitamin C (8, 13 and 19mg/100 g) and Anthocyanin (75, 72 and 86 mg/kg) in the strawberry samples dried by osmotic method, hot air oven and microwave methods, respectively. Dried strawberries using the microwave had lower moisture content, total sugar and a higher brix, vitamin C and anthocyanins than the samples dried with osmotic and hot air oven methods. On the other hand, from the viewpoint of sensory properties, dried strawberry using microwave and osmotic methods had better appearance, color, firmness and flavor in comparison with dried samples by hot air oven and control. Overall, dried strawberries using the microwave method had the lowest amount of moisture, vitamin C and the higher content of anthocyanins and sensory characteristics than the other drying methods. Therefore, in this study for producing of dried strawberries in comparison with the other drying methods, the microwave method was recommended.