Description
Determination of reducing sugars by Rebelein Titration:
1. Pipette 10.0mL of Z1 solution and 5.0mL of Z2 solution into an Erlenmeyer flask. Add a few boiling granules.
2. Pipette 2.0mL of wine sample into the flask.
3. Heat until boiling, allow to boil for 30 seconds. Remove the flask from the heat source and allow to cool to room temperature.
4. Add 10.0mL of each of Z3, Z4, Z5 solutions in that order.
5. Fill the burette with Z6 (standard thiosulphate solution)
6. Record the initial burette reading.
7. Titrate the mixture in the Erlenmeyer flask, shaking the flask well to mix throughout the titration.
8. The endpoint is cream. The solution will fade from yellow-brown (free iodine) to a blue-grey from the starch, before turning cream.
9. Record the final burette reading.
10. Carry out a reagent blank using 2.0mL of distilled water instead of wine, at the same time as the test sample. Treat the blank identically (steps 1-9).
11. Calculate the net titres for both the sample and the distilled water blank. The blank titre should be in the range 29-31mL. The sample titre will be less.
12. Calculate the reducing sugar content using the formula below. If no sample dilution was performed, the dilution factor = 1:
Reducing sugars (g/L)
= Dilution factor x [Blank titre(mL) – Sample titre(mL)]
Reviews
There are no reviews yet.