Candy - Determination of Reducing Sugar
1. Direct titration
2 Principle
After removing the protein from the sample, the calibrated alkaline copper tartrate solution was directly titrated under heating conditions, and the amount of reducing sugar was calculated based on the consumption volume of the sample liquid using methine blue as an indicator.
3 Reagents
3.1 Alkaline tartrate copper solution
Weigh 15 g of copper sulfate (CuSO4 • 5H2O) and 0.05 g of methine blue, dissolve in water and dilute to 1000 mL.
3.2 alkaline copper tartrate solution
Weigh 50g potassium sodium tartrate and 75g sodium hydroxide, dissolved in water, then add 4g potassium ferrocyanide, completely dissolved, diluted with water to 1000mL, and stored in a rubber stopper glass bottle.
3.3 Zinc acetate solution
Weigh 21.9 g of zinc acetate, add 3 mL of glacial acetic acid, dissolve with water and dilute to 100 mL.
3.4 Potassium Ferrocyanide Solution (10.6+89.4)
Weigh 10.6 g of potassium ferrocyanide, dissolve with water and dilute to 100 mL.
3.5 glucose standard solution (1mg/mL)
Precisely weigh 1.000 g of 98-100° C. to a constant amount of pure glucose, dissolve with water, add 5 mL of hydrochloric acid, and dilute with water to 1000 mL. This solution corresponds to 1 mg of glucose per milliliter.
3.6 Hydrochloric acid
4 Instruments
4.1 General Laboratory Instruments and Equipment
4.2 Oldham or G4 drape
5 Operation steps
5.1 Sample Processing
The sample is crushed and mixed until ready for use. The sample should be protected from exposure to air and sunlight and analyzed as quickly as possible.
Weigh about 2.5 ~ 5g sample, placed in a 250mL volumetric flask, add 50mL water, shake slowly add 5mL of zinc acetate solution and potassium ferrocyanide solution (10.6 + 89.4) 5mL, add water to the mark, and mix. Let stand for 30 minutes, filter with dry filter paper, discard the primary filtrate, and leave the filtrate for use.
5.2 Calibration of alkaline copper tartrate solution
Pipette 5.0mL of alkaline copper tartrate solution and 5.0mL of B, placed in a 150mL Erlenmeyer flask, add water 10mL, add 2 glass beads, add about 9mL of glucose standard solution from the burette, control in 2min heated to boiling, Continue boiling the glucose standard solution at a rate of 1 drop every 2 seconds until the blue color of the solution just fades to the end point. Record the total volume of the glucose standard solution consumed. Simultaneously perform three operations. Take the average value and calculate it every 10 mL ( A, B each 5mL) alkaline tartrate copper solution corresponds to the mass of glucose (mg).
5.3 Sample Solution Prediction
Pipette 5.0 mL of alkaline copper tartrate solution and 5.0 mL of EtOH in a 150 mL Erlenmeyer flask, add 10 mL of water, add 2 glass beads, and control to heat up to boiling within 2 min. Drop the sample solution from the burette and keep the solution boiled. When the color of the solution becomes light, titrate at a rate of one drop every two seconds until the blue color of the solution just fades to the end and record the volume of the sample solution.
5.4 Determination of sample solution 1
Pipette 5.0 mL of alkaline copper tartrate solution and 5.0 mL of ethyl acetate into a 150 mL conical flask, add 10 mL of water, add 2 glass beads, and add 1 mL of sample solution less than the predicted volume from the burette to heat within 2 minutes. To boiling, helium continues to titrate at a rate of one drop every two seconds until the blue color just fades to the end, recording the volume of sample fluid consumed, three times in parallel with the method to obtain the average consumed volume.
6 result calculation
Calculate the content of reducing sugar in candy by the following formula:×××=VmmX
Where: X - the content of reducing sugar in the sample (in terms of glucose),%;
M1 - 10mL alkaline copper tartrate solution (A, B each 5mL) corresponds to the amount of reducing sugar (based on glucose), mg;
M2 - sample quality, g;
V - Average sample solution volume consumed in the assay, mL.
7 Precision
The relative difference between two parallel measurements of the same sample must not exceed 15%.