Study of Physicochemical Properties of Dried Kiwifruits Using the Natural Hypertonic Solution in Ultrasound-assisted Osmotic Dehydration as Pretreatment

In this study, the effect of osmotic solutions (sugar solution, grape syrup and mulberry syrup) and ultrasound time (20, 30, and 40 min) was investigated on the water loss, solid gain, moisture content, shrinkage, firmness, color (L*a*b*), vitamin C, total chlorophyll, and sensory properties of dried kiwifruits. High performance liquid chromatography revealed that grape and mulberry syrups contained high amounts of invert sugar as fructose and glucose. The results showed that the use of grape syrup as pre-treatment reduced the moisture content, shrinkage and L* value of the kiwifruit slices while increasing the water loss, solid gain, firmness, vitamin C and total chlorophyll of the samples compared to other pretreatments. Moreover, with increasing ultrasonic time from 20 min to 40 min, moisture content, vitamin C, and total chlorophyll decreased whereas firmness increased in the samples. The results also demonstrated that the use of grape and mulberry syrups significantly improved the organoleptic characteristics of the dried kiwifruit slices.