3.2. Bioactive Compounds
Rice Formula 2 (before cooking) contained all levels of γ-oryzanol, α-tocopherol and phenolic substances of 42.91 mg/100g, 0.30 μg/ml and 0.85 mg GAE/g, respectively, which were higher than 29.15 mg/100g, 0.24 μg/ml and 0.43 mg GAE/g for Rice Formula 2 (after cooking), respectively (Table 2). When Rice Formula 2 was compared (before and after cooking), all levels of γ-oryzanol, α-tocopherol and phenolic substances were found to be different with statistical significance (p<0.05). Biological active compounds are lost during the cooking process at a temperature of 95°C because these substances are unstable under high heat and humidity [30]. Heating temperature and time eliminated substances with antioxidant properties in rice grains and may cause loss while the rice is rinsed before cooking because these substances contain good water solubility properties while α-tocopherol substance levels were no different with statistical significance (p>0.05), possibly because cooking rice at mildly reduced α-tocopherol levels leaves fewer benefits to be gained from significant substances in rice grains.
3.3. Antioxidant Activity
3.3.1. In Vitro
Comparison of the antioxidant activity of Rice Formula 2 with the DPPH method by comparing from concentrations of substances capable of suppressing DPPH• radicals at 50% (IC50) found Rice Formula 2
(before cooking) to have an IC50 value of 12.21 mg/ml, which was lower than 37.66 mg/ml for Rice Formula
2 (after cooking) while Rice Formula 2 (before cooking) was able to reduce iron atoms by the FRAP method at 3.27 μmol FeSO4/g, which was better than 3.03 μmol FeSO4/g for Rice Formula 2 (after cooking) (Table 2).
When antioxidant activity of Rice Formula 2 (before and after cooking) was compared by the DPPH and
FRAP methods, antioxidant activity was found to be different with statistical significance (p<0.05), thusindicating that Rice Formula 2 (after cooking) had significantly reduced antioxidant capabilities in every method. Antioxidant activity was related to all levels of γ-oryzanol, α-tocopherol, phenolic substances, carotenoid and anthocyanidin in rice grains with reduced values during the cooking process. Therefore, residual antioxidant activity in rice grains after the cooking process may be caused by substances with antioxidant properties not being completely eliminated.
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