Effect of oven and freeze drying on nutritional composition of pumpkin (<i>Cucurbita maxima</i>) processed flour

Abstract

Pumpkin is very perishable and drying is one of methods to preserve it. The objective of the present study was to evaluate the effect of oven and freeze-drying methods on the nutritional composition of processed pumpkin flours. Pumpkin fruit samples (A, B, C, D and E) of Cucurbita maxima species were collected from local markets within the country. They were oven dried at 65°C for 8 hours and freeze dried at 30°C for 4 days, and then processed into flours. The moisture content, total ash, crude protein and total carotenoids were analyzed in both fresh samples and processed flours according to AOAC approved methods. Data obtained from laboratory analysis were subjected to analysis of variance (ANOVA) at significant differences (P <0.05) between the nutritional contents of fresh samples, and of flours processed by oven and freeze drying. The study revealed that mean values for moisture, total ash and crude protein contents were 85.33, 7.62 and 12.78% for fresh pumpkin respectively; flour obtained by freeze drying contained 3.21, 6.25, and 9.35% respectively while by oven drying it was 1.19, 1.81, and 2.36% respectively. For total carotenoids, values were 180.13, 164.92 and 143.43μg / g_-1 respectively for fresh pumpkin, flour made by freeze drying, and flour made by oven drying methods. Generally, the nutritional contents of fresh sample, flour made by freeze drying and flour obtained by oven drying methods were significantly different (P <0.05). For the purposes of high yields of pumpkins flour, freeze drying could be the method of choice as it was found to give better results in terms of nutrients retention. The shelf life of the two flour batches should be studied in further research works.

Keywords: Pumpkin, Pumpkin flour, oven drying, freeze drying, nutritional value