The changes in the antioxidant capacity of selected tropical fruits upon treatment with gaseous ozone and ultraviolet c radiation
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Date
2009
Authors
Alothman, Mohammad Nazih Abdelrahman
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Abstract
The phenol content and antioxidant capacity of three tropical fruits pulps,
honey pineapple (Ananas comosus Merr), a local type of banana (Musa paradasiaca)
locally called pisang mas, and Thai seedless guava (Psidium guajava L.) was
studied. Three solvent systems were used (methanol, ethanol, and acetone) with three
different concentrations (50, 70, and 90%) and 100% distilled water. The effects of
UV-C and gaseous ozone treatments on total phenol, flavonoid, vitamin C contents,
and the antioxidant capacity of fresh-cut of the three fruits have been investigated
separately. During UV-C treatment, the fresh-cut fruits were irradiated for 0, 10, 20,
and 30 min. The fresh-cut fruits were exposed to gaseous ozone with the flow rate of
8 ± 0.2 ml/sec for 0, 10, 20, and 30 min. Total phenol and total flavonoid contents of
the fruits were measured using Folin-Ciocalteau and aluminum chloride colorimetric
methods respectively. The antioxidant activity of the fruit extracts was evaluated
using ferric reducing/antioxidant power (FRAP) assay and the free-radicalscavenging
effect on the DPPH radical assays. The efficiency of solvents used to
extract phenols from the three fruits varied considerably. Values of total phenol
content (on fresh weight basis) ranged from123.21 ± 4.45 to 190.58 ± 4.35 gallic
acid equivalents / 100 g (GAE/100 g) for guava fruits, from24.37 ± 2.45 to 72.21 ±
2.03 GAE/100 g for banana and from 34.65 ± 3.44 to 54.68 ± 1.79 GAE/100 g for
pineapple. High phenol content was significantly correlated with higher antioxidant
capacity. Both UV-C and gaseous ozone treatments were found to cause significant
changes in the total phenol, flavonoids, and vitamin C contents of the fruits with
different extents based on the type of fruit and treatment time. Total phenol and
flavonoid contents of guava and banana increased significantly with the increase in
UV-C treatment time, while the increase was insignificant in the total phenol of
pineapple fruits. Flavonoid content of pineapple increased significantly only after 10
min UV-C treatment. For gaseous ozone treatment, both total phenol and flavonoid
contents of pineapple and banana increased significantly with the increase in
treatment time up to 20 min, while it decreased in guava fruits with the increase in
treatment time. The antioxidant capacity of the fruits was affected significantly with
the UV-C and gaseous ozone treatments based also on the type of fruit and treatment
time. Both UV-C and gaseous ozone treatments decreased the vitamin C content of
the three fruits significantly.
Description
Master
Keywords
Industrial technology , Antioxidant capacity , Tropical fruits , Gaseous ozone