Effect of Steam Blanching on Carotenoids, Phenolic Compounds Content and Antioxidant Activity of Dried Pumpkin’s Pulp (Cucurbita moschata) Farmed with Three Biological Fertilizers

Abstract

Aims: This study aims to assess the effect of steam blanching on the phytochemical composition and the antioxidant properties of Cucurbita moschata pulp, obtained with the use of three biological fertilizers.  Study Design: The study was done on five samples of pumpkin pulp grown in different conditions. All the samples were evaluated before and after steam blanching treatment followed by hot                    air drying. The experimental design was a randomized complete block design with three replications.  Place and Duration of Study: Laboratory of Biochemistry-University of Douala, Cameroon. The duration of study was seven months, from March to September 2018. Methodology: Pumpkin were grown in May-September 2018 using the following fertilizers: ash at 10kg/25m2; bovine compost at 62.5 kg/25m2; ash + bovine compost (1:1). Besides negative control without fertilizers and positive control represented by NPK (20-10-10) at 2 kg/25m2 have been done. After harvesting, carotenoids, phenolic compounds, flavonoids contents, and antioxidant activities were determined using standard methods before and after a steam blanching treatment followed by hot air drying process.  Results: Pumpkin pulp fertilized with ash, after a steam blanching treatment had the highest contents of total carotenoids, β-carotene, lycopene respectively of 696.03 ± 7.57; 584.86 ± 15.50 and 115.00 ± 1.25 mg/100g of edible portion and the lowest percentages of loss of these bioactive compounds. Pumpkin pulp fertilized with bovine compost and ash showed the lowest rates of loss of total phenolic compounds, respectively 0.62% and 4.25%, while those fertilized with the positive control (NPK) showed the highest rate of loss of total phenolic compounds (60%). Steam blanching treatment had a significant impact on phytonutrient contents and total phenolic compounds extracted from dried pumpkin pulp exert greater antioxidant activity.  Conclusion: Pumpkin pulp fertilized with ash provides the highest carotenoids content after steam blanching treatment and this treatment increases the antioxidant activity and probably the shelf life of dried pumpkin pulp.