| dc.description.abstract | Pretreatments applied before drying have been proposed as an effective method to
improve the quality of dried fruit samples. In this study, the effects of different
pretreatments (ultrasound and microwave) combined with osmotic dehydration on
semi-dried pumpkin slices were evaluated. Samples were treated with ultrasound
(USOD) at different temperature (30oC, 40oC, 50oC) and different periods of time (30,
60, 90 minutes) while microwave (MWOD) at different powers (240 W, 400 W and
560 W) during 30, 60 and 90 seconds. USOD-50oC-30min and MWOD-560W-60s
were used as the most optimal conditions in this research based on the highest result
of WL/SG ratio. The Two-term model was used to describe the drying process of
pumpkin slices. USOD and MWOD showed effectiveness in significantly shortening
drying time to 499 and 510 minutes, respectively. Furthermore, they also showed
positive effects on improving product shrinkage, hardness and color. This leads to
good reviews for the product by panelists in the sensory analysis. However, significant
losses (p<0.05) of nutrients (total phenolic, antioxidant and carotenoids content)
compared to non-treated samples were also observed when pretreatment methods were
applied. Scanning electron microscopy (SEM) technique was used to analyze the
structural changes that are responsible for the differences mentioned. | en_US |
