Title : Effect of pretreatments and solar tunnel dryer temperature on proximate and bioactive components of pumpkin (Cucurbita maxima) pulp powder
Abstract:
Pumpkin (C. maxima) is rich in nutrients, adapts well to local conditions and grows in a wide range of agro-ecological zones. However, it is one of underutilized crop due to lack of enough information about its nutrient contents. In addition to this, the big size of the fruit makes difficult the use of the fruit for one-time cooking and the remaining pieces from days cooking prone to high after harvest loss. The loss is high due to absence of refrigerator in most households to store the remaining portions of the fruit. Production of the fruit is also seasonal and only available for few months. However, production shelf stable value added product from the pulp, reduce the postharvest loss, overcome limitations associated with storage and make the product available throughout the year. Therefore, this study was carried out to investigate the effect of pre drying treatments and solar tunnel dryer temperature (solar tunnel drier zones) on proximate and bioactive component of pumpkin pulp powder. Solar tunnel drier of 16 m long divided in to three zones considering temperature and RH variation along the dryer. The experiment consisted of three level of solar tunnel dryer temperature (45 ± 3.38, RH 34.58 ± 3.67, 54 ± 3.70, RH 31.36 ± 3.40 and 65 ± 3.20? 0C, RH, 24.16 ±3. 40% representing three zones (I, II, III) and four levels of pretreatments (control, 1% citric acid, 2% salt solutions and 2% salt blanched at 65 oC for 20 min) laid out in a 3×4 factorial arrangement using Randomized Complete Block Design. Pretreated slices (2mm) dried at three zones of solar tunnel dryer at above indicated temperatures to constant moisture content of three subsequent measurements. Results showed that, moisture content of dried powder varied from 6.4-8.2%, 4.7-6.2% in total ash, 1.1-4.2% in crude fat, and 2.4-4.2% in crude protein. The higher ash content could be corresponding to mineral elements concentration in the powder. Slices dried at highest solar drier temperature resulted in higher crude protein value pretreated with 2% salt solution. From the bioactive component the highest total phenolic content, beta carotene, L-ascorbic acid and total antioxidant activity were recorded for sample dried at 54 ± 3.70 0C pretreated with same salt solution. Dryer zone I representing relatively the lower temperature results in inferior results both in proximate and bioactive compositions. Therefore, creation of a more homogenous drying temperature and RH along the driers through mechanical mixing could result in a more uniform drying condition for better quality product.
Keywords: Bioactive, Proximate, Pumpkin, Solar Dryer, Blanched.
