| dc.description.abstract | There are many active functional compounds in citrus peels, such as flavonoid and phenolic acid.
This research investigated the effects of different drying temperatures (60, 70, 80, and 90oC) and
drying time (24, 32, 40 and 48h) on changes in the flavonoid, phenolic acid, and antioxidant
activities of Citrus sinensis peel tea. The total phenolic and flavonoid contents and antioxidant
activity of drying treated orange peels were increased by increasing drying temperature and time.
The phenolic compounds of orange peel with different temperature at constant 24h increased
significantly (total phenolic content increased from 10.78 to 37.87 mg GAE/g, total flavonoid
content increased from 8.49 to 14.15 mg RE/g and DPPH from 30.87% to 38.32%). Furthermore,
the phenolic compounds of orange peel with different times at constant 90oC also increased
significantly, which were total phenolic content increased from 37.78 to 52.11 mg GAE/g, total
flavonoid content increased from 14.15 to 18.26 mg RE/g, and DPPH from 38.32% to 49.29%,
respectively. By comparing oven drying samples with freeze drying which serves as control
sample, all samples treated with heat treatment always showed the higher TPC, TFC and TAC. As
a result, samples treated at 90oC in 48h treated sample extract were significantly higher in TPC,
TFC and TAC than the amounts in the samples heated at other treatments (P < 0.05). These results
indicated that the antioxidant activity of orange peel tea extracts was significantly affected by
heating temperature and duration of treatment on orange peel tea and that the heating process can
be used as a tool for increasing the antioxidant activity of orange peel tea. In terms of sugar syrup
treatments, orange peels were dipped in sucrose, glucose, fructose, and invert sugar syrup at
50oBrix for 24 hours, and then dried at 90
oC in 48h had the high score for overall acceptability of
customers which was 8.77 points. | en_US |
