2.6. Determination of antioxidant capacity
2.6.1. Ethanol extraction of antioxidants in whole grain
Barley flour (1 g) was extracted with 20 mL 80% ethanol at 45 C
in a flask placed in a 200 rpm shaking water bath for 4 h under dark
conditions. Vacuum filtration was then used to separate the supernatant,
which was stored in the dark at 20 C and analysed within
24 h using the DPPH free radical method (Omwamba & Hu, 2009).
2.6.2. DPPH free radical method
Barley flour extract (0.1 mL) was added to 2.9 mL of DPPH
(112 lM). After mixing, the sample was allowed to stand at 23 C
in the dark for 20 min. Reduction in absorbance was measured at
517 nm after 20 min using a spectrophotometer (UV/VIS SP 8001,
Metertech, Taiwan). Antioxidant capacity was then determined
using a standard curve for ascorbic acid and prediction models provided
by GenStat 14 and expressed as mg ascorbic acid equivalent
antioxidant capacity per 100 g of fresh weight of grain (mg AEAC/
100 g FW).
2.6.3. Determination of antioxidant capacity of vitamin E
The vitamin E was extracted as described previously
(Section 2.6.1). After extraction and drying using stream nitrogen,
1 mL n-hexane was replaced by 1 mL of 100% (v/v) ethanol to dissolve
the residue. The antioxidant capacity of the vitamin E
extracts was then determined using the DPPH free radical method
(Section 2.6.2).
2.6. Determination of antioxidant capacity2.6.1. Ethanol extraction of antioxidants in whole grainBarley flour (1 g) was extracted with 20 mL 80% ethanol at 45 Cin a flask placed in a 200 rpm shaking water bath for 4 h under darkconditions. Vacuum filtration was then used to separate the supernatant,which was stored in the dark at 20 C and analysed within24 h using the DPPH free radical method (Omwamba & Hu, 2009).2.6.2. DPPH free radical methodBarley flour extract (0.1 mL) was added to 2.9 mL of DPPH(112 lM). After mixing, the sample was allowed to stand at 23 Cin the dark for 20 min. Reduction in absorbance was measured at517 nm after 20 min using a spectrophotometer (UV/VIS SP 8001,Metertech, Taiwan). Antioxidant capacity was then determinedusing a standard curve for ascorbic acid and prediction models providedby GenStat 14 and expressed as mg ascorbic acid equivalentantioxidant capacity per 100 g of fresh weight of grain (mg AEAC/100 g FW).2.6.3. Determination of antioxidant capacity of vitamin EThe vitamin E was extracted as described previously(Section 2.6.1). After extraction and drying using stream nitrogen,1 mL n-hexane was replaced by 1 mL of 100% (v/v) ethanol to dissolvethe residue. The antioxidant capacity of the vitamin Eextracts was then determined using the DPPH free radical method(Section 2.6.2).
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