| dc.description.abstract | This study was carried out to examine the effect of different pretreatments (hot water
blanching, steaming and starch coating) and their parameters on the physical,
chemical, and microstructural properties of semi-dried pumpkin slices. The slices were
pretreated and dried at 70°C and were taken to measure the value of hardness,
shrinkage, color, total carotenoids, total phenolic content, and antioxidant capacities
by both DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-Azino-bis (3-
ethylbenzothiazoline-6-sulfonic acid) radial scavenging assays. For microstructural
characterization, Scanning Electron Microscopy was used. Mathematical modelling of
the drying curves of each pretreated sample was also investigated by fitting
experimental data to Midilli equation. All the R2 values obtained were consistently
high throughout all the samples (>0.99), suggesting that the model chosen was a
good fit for the drying of this product. All pretreatments were found to be effective
for bioactive compounds preservation, with highest values for all chemical properties
measured (total phenolic content, total carotenoids, antioxidant capacities) belonged
to samples coated with 1% corn starch. As for physical characteristics, hardness
values were reduced by all the pretreatments; however, smallest hardness values
were obtained in thermal pretreatments with values ranging from 5.99 to 10.38 N.
Highest shrinkage extent was caused by steaming and hot water blanching (55.53-
60.05%) while starch coating kept the area of the sample well maintained (30.94-
49.27%). Color changes were observed to be most significant in thermally pretreated
samples with ∆E value ranging from 37.00 to 46.76. Sensory evaluation results
showed that all pretreatments gave relatively positive effect on the sensory
properties; however, starch coated samples were found to be consistently highest in
value throughout the characteristics investigated. According to this project’s results,
steaming, blanching and starch coating could efficiently improve the quality of semi dried pumpkin slices. However, starch coating should be practiced more as a novel
technique since the results had proven this method to be superior in all properties. | en_US |
