THE EFFECT OF HIGH INTENSITY ULTRASOUND PRE-TREATMENT ON THE FUNCTIONAL PROPERTIES OF MICROWAVE-DRIED PEARS

Abstract

The objective of this study was to investigate the impacts of high intensity ultrasound (HIU) pre-treatment on the quality of microwave-dried pears. Functional properties including color and bioactive compounds (total phenolic content (TPC) and antioxidant capacity (ATC)) of microwave-dried pears at 2 power levels (100 and 200 W) with and without HIU-pretreatment were compared with the untreated pears. A Konica Minota CR-400 Chroma Meter was used to examine the color changes in microwave-dried pears. TPC was measured using the Folin-Ciocalteu reagent. The free radical scavenging activity of the extract was analyzed using 1,1-dipheyl-2-picylhydrazyl (DPPH). It was concluded that the TPC and ATC of microwave-dried pears treated with and without HIU pre-treatment under both power levels were decreased in comparison with untreated pears. The highest phenolic substances were observed in a HIU pre-treated (20 min) and dried at 200 W pear pieces. Similarly, the ATC of microwave-dried pears at 200 W with HIU pre-treatment were higher than those of the samples processed with microwave drying at 100 W for both HIU-treated and untreated samples. All colour parameters (L*, a*, b*)were shown a significant change depending on the drying powers and application of HIU pre-treatment. The closest color values to the fresh sample were found for the microwave-dried samples at 200 W with HIU pre-treatment during 20 min. In overall, microwave drying process was proven to be more effecient when combined with HIU-pretreatment to acquire a high-quality food product along with an enhanced bioactive components & color.