Effects of ultrasonic-assisted pretreatments on quality attributes of dried carrot slices (Daucus carota)

Pretreatments are widely used before drying horticultural products to enhance the drying efficiency, improve quality and prolong the storage life of the dried products. This study investigated the effect of ultrasonic-assisted edible coating pretreatment on the physical, phytochemical and antioxidant properties of oven-dried carrot slices. Fresh carrots were processed into slices and dipped in 3% gum arabic (GA), ethanol (100%) and water (control), followed by ultrasonication (25°C and high frequency) for 10 min. The pretreated samples were then oven-dried at 50°C until 10% moisture content was obtained. Physical (colour, hardness, rehydration capacity), phytochemical (total phenolic content (TPC), β-carotene) and radical scavenging properties (DPPH radical scavenging activity) were investigated. TPC ranged from 11.5 (control)-33.2 mg gallic acid equivalent 100 g^-1 dry matter (mg GAE 100 g^-1 DM) (GA), while β-carotene content in the dried carrots ranged between 5.98 (control)-12.99 mg β-carotene equivalent 100 g^-1 DM (GA). Pretreatment with gum arabic had the highest DPPH radical scavenging activity of the dried carrot slices (81.65), and the unpretreated sample had the lowest value (55.5 mM ascorbic acid equivalent 100 g^-1 DM). The study demonstrated that ultrasonic-assisted GA pretreatment coating improved the quality integrity of the dried carrot slices.