Abstract
Gac fruit (Momordica cochinchinensis (Lour.) Spreng) has high content of bioactive
compounds, especially carotenoids. These carotenoids are currently in special demand as
they are natural antioxidants with potential to prevent chronic disease such as cancers. The
objective of this research was to study the effect of pre-treatment and drying temperature
on physical properties of gac powder. Bioactive compounds (total carotenoid content) and
antioxidant activity of gac powder were investigated. Gac aril and pulp mixture, or gac peel
samples were applied with different pre-treatment (blanching or soaking in ascorbic acid)
and dried by tray dryer at 50 or 60ºC until the moisture content reached 6%. Bulk density
of the samples was in the range of 0.3691-0.6920 g/mL. The highest water solubility index
(WSI) was found in aril and pulp mixture sample soaked in ascorbic acid and dried at 50°C
(43.70± 2.25 %) (p<0.05). The aril and pulp mixture with blanching and dried at 50ºC showed
the highest redness (a*) (26.01±0.15), with lightness (L*) of 23.55±2.43 and yellowness (b*)
of 33.87±0.82 (p<0.05). In addition, aril and pulp mixture sample, blanched and dried at
50ºC had the highest value in total carotenoid content (93.49±11.35 mg β-carotene/100
mL samples), total phenolic compound (467.44±7.64 µg GAE/g), DPPH (43.57±1.61 mmol
Trolox/100g) and FRAP value (598.22±18.59 µmol AAE/100g) compared to other samples
(p<0.05). In conclusion, using blanching as pre-treatment and drying temperature at 50°C
could prevent the loss of bioactive compounds and antioxidant activity of the gac aril and
pulp mixture during tray drying process. The finding of this study could be applied in the
waste utilization process from gac fruit.
