Effect of pretreatment and temperature on the drying kinetics and physicochemical and techno-functional characteristics of pumpkin (Cucurbita maxima)

Abstract

The study was carried out to assess fresh slices and thermally pretreated pumpkin ( Cucurbita maxima ) dried at temperatures of 55 °C, 60 °C, 65 °C, and 70 °C. The drying kinetics and quality attributes of the dried product were determined, and results indicated that the modified Page model was the best fit, with activation energies of 29.47 kJ mol −1 and 16.06 kJ mol −1 for drying fresh and thermally pretreated slices, respectively. A significant effect (p < 0.05) related to thermal pretreatment and temperature was evidenced on the physicochemical properties. The fresh pulp powders presented the following ranges of moisture and color (ΔE), 7.10%–8.31% w.b.; 21.23–25.23, respectively, and for the pretreated pulp powders, they were 8.94%–11.54% w.b., and from 19.00- 28.30, respectively. There were no significant effects on the techno-functional properties in the powders; cold water solubility was 5.36%–6.46%, water absorption capacity was 3.42–6.52 g/g, and oil absorption capacity was 1.00–1.30 g/g. The carbohydrate and fiber contents significantly decreased in the pretreated powder. An increase in antioxidant activity was found in fresh and thermally pretreated pulp powder at a temperature of 70 °C, presenting values between 2.23-2.98 μmol Trolox equivalent g −1 d.b. evaluated by the DPPH method and between 40.48-45.92 μmol Trolox equivalent g −1 d.b. by ABTS, and no significant differences (p > 0.05) were determined after pulp pretreatment. The total content of carotenoids presented retention percentages for fresh pulp powders of 52.09%, 41.92%, 30.55%, and 22.79%, while for pretreated pulp powders, they were 30.67%, 32.86%, 24.84%, and 14.71% when dried at temperatures of 55 °C, 60 °C, 65 °C, and 70 °C, respectively. The powders obtained from heat-pretreated pumpkin pulp showed significant differences (p < 0.05) in physicochemical characteristics and total carotenoids, but they were not found (p > 0.05) in the techno-functional properties and antioxidant activity evaluated by the DPPH and ABTS methods.

Drying kinetics of guabiju pulp (Myrcianthes pungens): Mass transfer parameters, mathematical modeling and evaluation of bioactive compounds

“…Through the Arrhenius equation, (Figure 2) shows an activation energy ( E a ) of 30.77 kJ mol −1 and an Arrhenius factor ( D o ) of 1.962 × 10 −4 m 2 s −1 were obtained for the drying process of the guabiju pulp. This value is within the general range from 12.7 to 110 kJ mol −1 obtained in foods (Zogzas et al, 1996), and close to dried fruits and vegetables: pumpkin slices (29.47 kJ mol −1 ) (Márquez‐Cardozo et al, 2021), banana (41.53 kJ mol −1 ) (Macedo et al, 2020), and red pepper (37.76 kJ mol −1 ) (Kaleemullah & Kailappan, 2006).…”

“…Removal of water decreases enzymatic and microbial activity, contributing to increase the shelf life. However, drying can significantly affect the bioactive compounds (Márquez-Cardozo et al, 2021).…”

“…Removal of water decreases enzymatic and microbial activity, contributing to increase the shelf life. However, drying can significantly affect the bioactive compounds (Márquez‐Cardozo et al, 2021). The production of dried guabiju is an economic and technological alternative, for the best use of fruit growing, and can be marketed as a product for direct consumption or as an ingredient in the food, pharmaceutical or chemical industries.…”

Impact of blanching treatments on the chemical composition, total dietary fiber, physicochemical, functional, and structural properties of underutilized cauliflower leaves ( Brassica oleracea var. botrytis )

“…According to Devisetti et al (2016) water binding capacity is important in bulking, swelling, and consistency of products and also baking applications. Thus, cauliflower leaf powder has a high potential for use in food products such as bakery products, beverages, gravies, soups, and sauces due to its high WAC where bulking and thickening could be due to the breakdown of starch molecules that facilitate the development of new H bond (hydrogen) with water molecules (Márquez Cardozo et al, 2021). Steam blanching and hot water blanching led to decreased water solubility in the dried cauliflower leaf compared to the unblanched sample.…”

“…Pretreatment processes before drying can be applied to agricultural products to enhance product quality. Hot water blanching and steam blanching is one such pretreatment method widely used in food processing for the primary purpose of enzyme inactivation, retention of nutrients, and color enhancement (Márquez‐Cardozo et al., 2021). Blanching can accelerate the rate of drying, which in turn helps to lower the time required for drying.…”