Effect of Drying Methods (Hot Air Drying and Freeze-drying) on the Nutritional Components and Antioxidant Activities of Abelmoschus esculentus (L.) Moench Extracts

This study evaluated and compared the nutritional components and antioxidant activities of Abelmoschus esculentus (L.) Moench (AM) extracts processed using hot air and freeze-drying methods. The results showed that hot air and freeze-dried AM extracts were mainly composed of carbohydrates and crude protein. Both hot air and freeze-dried AM had a high content of saturated fatty acids (palmitic acid). Also, both these extracts had a high content of unsaturated fatty acids (oleic acid and linoleic acid). The ratio of essential amino acids (EAA)/amino acids (AA) was higher in the hot air dried AM extract compared to the freeze-dried AM extract. Both the drying methods resulted in high content of potassium (K), followed by calcium (Ca) and magnesium (Mg) in decreasing order. Freeze-dried AM extract showed higher total polyphenol content compared to hot air dried AM extract. Total flavonoid content was significantly higher in hot-air dried AM extract compared to freeze-dried AM extract. The IC50 value for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity with hot-air dried and freeze-dried AM extract was found to be 0.78 and 0.69 mg/mL, respectively. The IC50 value for 2,2‘-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and the reducing power of freeze-dried AM extract were lower than that of hot-air dried AM extract. Ferric reducing antioxidant power (FRAP) was significantly higher in the freeze-dried AM extract than in the hot air dried AM extract. According to our results, it appears that AM extracts possess higher nutritional and antioxidant activities.