engleski

Influence of convective drying and ultrasound-assisted extraction on the recovery of proteins and sugars from pumpkin pulp (Curcurbita maxima D.) and its fractions

Drying is an important method to prevent post-harvest losses of pumpkin fruit and to obtain a more stable pumpkin powder. Pumpkin powder has a longer shelf life, desirable sweet taste and yellow-orange color, and could be used as a functional ingredient and natural color additive due to its nutritional and health-promoting properties. The simultaneous separation of pumpkin pulp for drying purposes resulted in large amounts of the waste fractions, i.e., the peel and seeds. Considering the nutritional potential of all pumpkin (Cucurbita maxima Duchese) products, i.e. pulp, dried pulp and by-products, the aim of this work was to compare the amounts of proteins and sugars obtained from them. Drying was carried out at temperatures of 50, 60 and 70 °C and air velocity of 0.5 m/s. To maximize the recovery of proteins and sugars from the pumpkin samples, ultrasound-assisted extraction was performed at a frequency of 37 kHz and a temperature of 50 °C for 10, 20, and 40 min. The results showed that all dried pumpkin pulp samples contained significantly higher amounts of proteins (7.80-12.67%) than raw pulp (1.03-2.30%), making them a potential source of nutrients. As the results show, a drying temperature of 60 °C can be considered optimal for protein extraction during 20 minutes. The optimal time for sugar extraction with ultrasonic treatment was set at 40 minutes with mass fractions of 49.39%, 49.70%, and 49.44% at temperatures of 50, 60, and 70 °C, respectively. Obviously, the dried samples are a valuable source of sugar compared to the raw pumpkin, which contains 2.99-5.61% sugar depending on the extraction time. The protein and sugar content is also higher in the pumpkin by-products than in the raw pulp. The results show that the amounts of sugars are 1.10-1.79% (seeds) and 4.86-9.11% (peels) and proteins are 4.31-4.76% (seeds) and 1.87-7.54% (peels), depending on the extraction time. In conclusion, all pumpkin components studied in this work can be considered as a valuable source of nutrients. Considering that seeds and peels are usually discarded, both by-products are interesting from a nutritional point of view and could be reused in line with global sustainable trends in the use of food by-products.

Cucurbita maxima ; dried pumpkin ; pumpkin by-products ; ultrasound assisted extraction ; nutritional profile

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