7.3.5.3 Chemicals and reagents
• Ethanol 78% (diluted, Agrar-Alkohol, Vienna, UN1170, C-K25V)
• Thermostable α-amylase (Megazyme Kit, Total starch)
• Sodium acetate buffer (100 mM, pH 5.0)
• Amyloglucosidase (Megazyme Kit, Total starch)
• GOPOD reagent (Glucose Determination Reagent)
• D-glucose standard solution (1 mg/ml, Megazyme Kit, Total starch)
7.3.5.4 Procedure
Approximately 100 mg ± 0.1 mg of each sample were weighed into glass test tubes
(triple determination) and 0.2 ml of aqueous ethanol (78%) was added to each tube to
wet the sample and aid dispersion. The tubes were stirred on a vortex mixer.
Immediately 3 ml of thermostable α-amylase (diluted 1:30 in 100 mM sodium acetate
buffer, pH 5.0) were added. Then, the tubes were incubated in a bowling water bath
for 6 min (vigorously stirring all 2 min). Accordingly, the tubes were placed in a water
bath at 50 °C, 0.1 ml amyloglucosidase was added and then, the tubes were stirred and
incubated at 50 °C for 30 min. Subsequent, the entire contents of the test tube were
transferred to a 100 ml volumetric flask (tubes were rinsed with distilled water),
adjusted with distilled water and mixed. Then, an aliquot of the solution was centrifuged at 3.000 rpm for 10 min and 0.1 µl of the clear, undiluted filtrate (duplicate
aliquot) was transferred to the bottom of a glass test tube. Then, 3 ml of GOPOD
reagent were added to each tube and incubated at 50 °C for 20 min.
Preparation of D-glucose control and reagent blank solution:
D-glucose control: 0.1 ml of D-glucose standard solution (1 mg/ml) and 3.0 ml of
GOPOD Reagent.
Reagent blank solution: 0.1 ml of water and 3.0 ml of GOPOD
The samples were transferred into macro-cuvettes and for each sample (including Dglucose
control) the absorbance at 510 nm was read against the reagent blank. The
starch content was calculated according to eq. 7.
7.3.5.3 Chemicals and reagents• Ethanol 78% (diluted, Agrar-Alkohol, Vienna, UN1170, C-K25V)• Thermostable α-amylase (Megazyme Kit, Total starch)• Sodium acetate buffer (100 mM, pH 5.0)• Amyloglucosidase (Megazyme Kit, Total starch)• GOPOD reagent (Glucose Determination Reagent)• D-glucose standard solution (1 mg/ml, Megazyme Kit, Total starch)7.3.5.4 ProcedureApproximately 100 mg ± 0.1 mg of each sample were weighed into glass test tubes(triple determination) and 0.2 ml of aqueous ethanol (78%) was added to each tube towet the sample and aid dispersion. The tubes were stirred on a vortex mixer.Immediately 3 ml of thermostable α-amylase (diluted 1:30 in 100 mM sodium acetatebuffer, pH 5.0) were added. Then, the tubes were incubated in a bowling water bathfor 6 min (vigorously stirring all 2 min). Accordingly, the tubes were placed in a waterbath at 50 °C, 0.1 ml amyloglucosidase was added and then, the tubes were stirred andincubated at 50 °C for 30 min. Subsequent, the entire contents of the test tube weretransferred to a 100 ml volumetric flask (tubes were rinsed with distilled water),adjusted with distilled water and mixed. Then, an aliquot of the solution was centrifuged at 3.000 rpm for 10 min and 0.1 µl of the clear, undiluted filtrate (duplicatealiquot) was transferred to the bottom of a glass test tube. Then, 3 ml of GOPODreagent were added to each tube and incubated at 50 °C for 20 min.Preparation of D-glucose control and reagent blank solution:D-glucose control: 0.1 ml of D-glucose standard solution (1 mg/ml) and 3.0 ml ofGOPOD Reagent.Reagent blank solution: 0.1 ml of water and 3.0 ml of GOPODThe samples were transferred into macro-cuvettes and for each sample (including Dglucosecontrol) the absorbance at 510 nm was read against the reagent blank. Thestarch content was calculated according to eq. 7.
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