Effect of Drying Techniques on Antioxidant Capacity of Guava Fruit

Abstract

Frequent consumption of fruits and vegetables has been associated with low risk of chronic diseases. Guava ( Psidium guajava Linn. ) is a tropical, seasonal fruit rich in antioxidants, vitamin C and polyphenol compounds. Drying is one of the common methods to preserve and extend the shelf life of guava. The objective of this study was to determine the effect of drying techniques on the antioxidant activity of guava fruit. Guava was air dried in air dryer (45°C), freeze dryer and by osmatic drying techniques. Fresh guava extracts (FGE), freeze dried guava extracts (FDGE), oven dried guava extracts (ODGE) and osmotic-dehydrated guava extracts (OSGE) guava extracts were prepared and analyzed for total polyphenols (TP), flavonoids, antioxidant potential by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), trolox equivalent antioxidant capacity (TEAC), total antioxidant capacity (TAC) and nitric oxide radical scavenging activity (NORS). Inhibitory potential of guava extracts on enzymes α-glucosidase, α-amylase and lipase was also determined. TP in FG, FD, OD, and OS were 415.69 ± 56.95, 295.30 ± 4.11, 303.57 ± 1.41, and 182.93 ± 6.48 mg gallic acid equivalent (GAE)/100g, respectively. Flavonoids in Fresh, FD, OD, and OS were 202.01 ± 0.16, 96.93 ± 1.73, 105.07 ± 0.58, and 76.13 ± 2.74 mg catechin equivalent (CE)/100 g, respectively. FD extracts were the most effective in scavenging DPPH radical. Whereas FRAP, TEAC and TAC activities were found to be higher in FG followed by OD and FD. However, NORS activity of FD was significantly (p ≤ 0.05) lower compared to other treatments. Inhibition of α-glycosidase, α-amylase and lipase enzymes was (19% - 90%) observed at 0.4, 0.8, and 0.8 mg/ml, respectively. In conclusion, considering this in-vitro study, drying could be effectively utilized to preserve guava fruit with minimum effect on health benefits.