Question

Describe a test to show that a food sample contains glucose

Answer 1

Answer and Explanation:

To test the presence of glucose, we can perform Benedict's test. This test detects the presence of reducing sugars (e.g. glucose) by adding Benedict's reagent. This reagent contains sodium carbonate, sodium citrate and copper(II) sulfate pentahydrate. When the mixture is heated, reduce cupric compounds (Cu2+) are formed which results in the change in color from clear blue to brick-red, yellow or green.

To test the presence of glucose in the food sample, we will dissolve a small volume of food sample in water and put it in the test tubes, in triplicates. Then we will add 3 mL of Benedict's reagent. Also, we will run positive and negative controls. For positive controls, we will add glucose directly and for negative, we will not add any glucose or other reducing sugars (also in triplicates each). Then we will heat the test tubes in water water for 5-10 minutes. In the positive control, the color would change to green, yellow or brick red; but in negative control, it will stay blue (see figure attached for explanation). For the food sample, if the glucose or reducing sugars would be present, the color will change. In case of low sugar, it will be green, but increasing sugar content would change the color to yellow/orange and red. Because the experiment will be conducted in triplicates, we would be also able to verify if the results were consistent and there was no human or technical error.