Effect of different pretreatments and drying techniques on some chemical and bioactive components of pumpkin fruit pulp

Abstract EN

The present work was conducted to evaluate the effect of unblanched (U), steam blanched(SB), osmotic dehydration(OS) and microwave (MW) as pretreatments and convective air drying as well as freeze-drying (F) as drying methods to prepare pumpkin pulp powder.

The proximate chemical composition, total, reducing and non-reducing sugars, dietary fiber, some bioactive compounds and antioxidant activities of pumpkin pulp powder were determined.

The results showed that the moisture content of the dried pumpkin pulp could be arranged in a descending order as follow: microwave MW, SB, U, F and finally OS.

The previous mentioned dehydration processes removed 86.44, 86.83, 88.75, 89.22 and 91.47% of the initial water content leading to final moisture content of 12.33, 11.97, 10.23, 9.8 and 7.75 % , respectively.

Pumpkin pulp is considered as a rich source of some bioactive compounds.

Carotenoids as β-carotene, polyphenols, flavonoids and ascorbic acid content were 24.73 mg /100g, 120.22 mg GAE / 100g, 24.73 mg RE / 100g and 181.21 mg / 100g on D.

W, respectively.

All treatments caused increment in β-carotene and polyphenol content except osmotic dehydration that caused pronounced decrement.

Flavonoid content increased to reach 33.07 mg (rutin equivalent )RE/100g by steam blanching, while, all the other treatments caused decrement.

Ascorbic acid was dramatically decreased by all treatments.

Except the OS dehydration sample, the free radical scavenging activity by DPPH(1, 1-Diphenyl-2picryl-hydrazyl) method varied between 49.7 in case of freeze drying to 69.34% in case of MW sample.

On the other hand, IC₅₀ values varied from 14.42 to 53.59 mg/ml.