engleski

Influence of convective air drying on the chemical composition of pumpkin pulp (Cucurbita maxima D.)

Pumpkin is a fruit vegetable that is commonly cooked, baked and processed into various pumpkin products in the food industry, such as pumpkin pie, bread, cookies, cheesecake, desserts, donuts, cereals, ice cream, lasagna dishes, etc. Due to the large global production and use, it is necessary to use preservation methods that allow to preserve the properties of pumpkin for a long period of time. One of the most commonly used methods is convective hot air drying, which reduces water activity and thus minimises microbiological changes. However, during the drying process, structural and chemical changes may occur in the fresh material, which eventually affect the product quality. Therefore, with the aim of extending the shelf life of fresh pumpkin pulp (Cucurbita maxima D), hot air drying was also used in this work. Experiments were conducted at three different temperatures (50, 60, and 70 °C) and speeds (1.5, 1.0, and 0.5 m/s) using the following combined parameters: 50 °C (1.5, 1.0, and 0.5 m/s), 60 °C (1.0 and 0.5 m/s), and 70 °C (0.5 m/s). The chemical properties of the dried samples were evaluated based on moisture content, crude ash, crude fat, and crude fibre content. To evaluate the chemical composition of the dried samples and the efficiency of drying, analyses were also performed on fresh, undried pulp. In addition to the dried and undried pumpkin samples, the peel and seeds were also analysed as potential sources of nutrients, which are by-products of the preparation of fresh pulp for drying. As the result showed, pumpkin pulp and peel contained significantly higher moisture content (93.97 and 87.78 %, respectively) than dried pulp (11.78 - 19.55 %, depending on temperature and drying speed) and seeds (9.81%). The highest ash content is found in dried pumpkin peel (5.55 - 8.23 %), followed by pulp (0.55 %), peel (0.97 %) and seeds (2.75 %). The fat and total fibre content are particularly high in pumpkin seeds, 21.44% and 56.55%, respectively. The high fat (3.24%) and fibre (18.52%) content is also found in the shell. Therefore, both by-products can be considered as valuable sources of fat and fibre, compared to dried samples with slightly lower amounts of these nutrients (1.03 - 3.13 % for fat) and (8.52 - 13.99 % fibre). In conclusion, the drying process resulted in a decrease in moisture content, which increased the shelf life of the squash. The dried samples are likely an excellent source of minerals due to their high ash content compared to the other samples. Although the fat and fibre content decreased due to the drying process, the results obtained indicate that the functional properties of the pumpkin can be maintained after drying.

pumpkin pulp ; dried pumpkin ; pumpkin by-products ; hot air dying ; chemical composition

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