Effect Of Different Pretreatments On The Quality Of Semi-Dried Pumpkin Slices

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.