To Determine the Different Glucose Contents Present in Different Juices

Experiment #: 3

Date: October 9, 2015

Topic: Semi-quantitative tests for reducing sugars

Aim: To determine the different glucose contents present in different juices.

Apparatus:

15 boiling tubes, test-tube rack, 5cm3 syringe, 1 cm3 syringe, distilled water, water bath, 4 small beakers, filter funnel, martyr and stencil , pipettes, marker pen, Benedict’s solution, ribena, pineapple and apple berry juice.

Method:

1. Five test-tubes were labeled 1 to 5. Using a 1cm3 syringe, 1cm3 of 10% glucose solution was placed in test-tube 1.

2. Using a 1cm3 syringe, 0.5cm3 of the 10% glucose solution was taken from a beaker and it was transferred to test-tube 2. Using a 1cm3 syringe, 0.5cm3 of distilled water was transferred to test-tube 2 and the contents were shaken and a 5% glucose solution was made.

3. Using a 1cm3 syringe, 0.2cm3 of glucose solution was taken from a beaker and transferred to a test-tube marked 3. Using a 1cm3, 0.8cm3 of distilled water was transferred to test-tube 3 and it was shaken and a 2% glucose solution was made.

4. The steps in 3 were repeated to make 1% and 0.5% glucose solutions by decreasing the amount of 10% glucose solution and more distilled water was added.

5. Using a 5cm3 syringe, 5cm3 of Benedict’s solution was added to each tube and the tubes were placed in a water bath for 9 minutes.

6. The tubes were removed from the water bath and returned to the test-tube rack where the colours obtained were recorded in a table.

Testing for the concentration of reducing sugars in some juices

1. Ribena was placed in a martyr and crushed using a stencil. The juice was then removed, filtered and placed in a beaker.

2. The step was repeated for the pineapple however, the apple berry juice did not need to undergo this method.

3. Using a 1cm3 syringe, 1cm3 of each juice was placed in a test-tube.

4. Using a 5cm3 syringe, 5cm3 of Benedict’s solution was added to each tube and they were placed in a water bath for 9 minutes.

5. The tubes were removed from the water bath and they were returned to the test-tube rack where the colours obtained were recorded in a table and was compared to the previous colours.

TABLE SHOWING THE COLOUR CHANGE THAT OCCURRED WITH THE DIFFERENT CONCENTRATION OF GLUCOSE AND JUICES WITH THE BENEDICT’S SOLUTION

SCALE/% COLOUR CHANGE APPLE BERRY PINE RIBENA

10 Brick-red X X X