Objectives: To identify which carbohydrates contain reducing sugars
Background: Some sugars have a free aldehyde or ketone group which makes them capable of acting as a reducing agent. We call these sugars reducing sugars. They play an important role in developing food colors and flavors during processing. Reducing sugars produce a brick-red color when heated in the presence of Benedict’s reagent.
- 1% solutions of carbohydrates (maltose, D-arabinose, sucrose, lactose, gum arabic, D-fructose, D-galactose and starch)
- Benedicts reagent
- Test tubes
- Test tube rack
- 400 ml beaker
- Distilled water
- 10 ml Measuring cylinder
- Prepare a boiling water bath by collecting approximately 200 ml distilled water in a 400 ml beaker and bring to boil (be sure to add 2-3 boiling stones in the water to prevent splattering
- While the water bath is getting ready, label test tubes from 1 through 8 or with an appropriate code corresponding to each of the 1% carbohydrate solutions
- Add 1 ml of each solution to the test tube
- Add 2 ml of Benedict’s reagent to each of the tube and mix by gentle shaking
- Place each tube in the boiling water-bath for about 5 minutes
- Remove the tubes and place them on the test tube rack
- Describe and record the final color of the solution and indicate whether each sample should be classified as a reducing sugar (develop an appropriate table to clearly and effectively illustrate your findings)
- Describe the principle of Benedict’s reagent test
- What makes some sugars reducing sugars while some are not?
- Did the reducing sugars produce different color intensities? If so, what would this indicate?