• Appearance: Slightly pale grayish brown ~ brown, crystals ~ powder
• Activity: shown on each label
• Molecular Weight: 57,000
• Optimum pH: 4.0 ~ 5.0

Assay
< Principle >
Starch + H₂O -(beta-Amylase)-> Maltose

< Reagents >

• Reagent A

1.08 g of Sodium Acetate, Trihydrate is dissolved in deionized water to make the 400 mL solution. Adjust to pH 4.8 with Acetic Acid (1+2). After that, add deionized water to make the 500 mL solution.
• Reagent B

0.5 g of 3,5-Dinitrosalicylic Acid is dissolved in 0.5 mol/L NaOH. 15 g of Sodium Potassium Tartrate, Tetrahydrate is added into the solution by degrees. Then, add deionized water to make the 50mL solution (Keep Reagent B in a refrigerator),
• Reagent C

10 mg/mL Substrate Solution
1g of Starch, Soluble is dissolved in 40 mL of Reagent A. Bring to a boil and maintain the solution for 1 minute. After that, cool it and adjust to pH 4.8 with Acetic Acid (1+2) or 0.1 mol/L NaOH.
• Reagent D

100 ug/mL beta-Amylase Enzyme Solution <ug: microgram>
Measure 25 mg of this product (beta-Amylase) accurately and add it into a 25mL-volumetric flask. Add Reagent A to make the 25 mL solution. Take the 5 mL with a volumetric pipette and add it into a 50mL-volumetric flask. Add Reagent A to make the 50 mL solution.
• Reagent E

10umol/mL Standard Solution
Measure 0.180g of Maltose accurately and add it into a 50mL-volumetric flask. Add Reagent A to make the 50 mL solution.

• Test

Reagent	Test	Blank
C	1 mL	1 mL
A	0.8 mL	0.8 mL
B	-	2.0 mL
D	0.2 mL	-
			Incubate for exactly 3.0 min. at 25C.
B	2 mL	-
D	-	0.2 mL
			Place in a boiling water bath for 5 min., then cool on ice.
Water	46 mL	46 mL
			Record the A490nm for both the Test and Blank using water as control.

• Standard Curve

Reagent	Std 1	Std 2	Std 3	Blank
E	0.1 mL	0.2 mL	0.3 mL	-
A	0.9 mL	0.8 mL	0.7 mL	1 mL
C	1 mL	1 mL	1 mL	1 mL
B	2 mL	2 mL	2 mL	2 mL
					Place in a boiling water bath for 5 min., then cool on ice.
Water	46 mL	46 mL	46 mL	46 mL
					Record the A490nm for both the Test and Blank using water as control and make the standard curve.

• Unit Definition
  One unit will liberate 1 micromole of maltose from starch in 1 minute at pH 4.8 at 25 degrees C.

• Calculations
  units/mg = ( a )/[ S x (5/25) x (0.2/50)] x (1/3)
  
  a: an amount of maltose liberated using the Standard Curve (micromole)
  S: weighed amount of this product (mg)