• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Food Test. Aim: To conduct tests for reducing and non-reducing sugars, starch, lipids and proteins

Extracts from this document...

Introduction

Transfer-Encoding: chunked ´╗┐Title: Food Test Aim: To conduct tests for reducing and non-reducing sugars, starch, lipids and proteins Introduction: Reducing sugars are disaccharides formed by the reaction of the aldehyde group of one monosaccharide with a hydroxyl group of another free aldehyde group. Reducing sugars such as glucose are simple sugars while non-reducing sugars such as sucrose are complex sugars. They are both soluble in water, sweet in taste and turns blue Benedict's solution to brick-red with a precipitate upon boiling. Moreover, starch is soluble in water and turns iodine solution from yellow-orange to blue-black. Proteins such as meat, fish and egg are large chemical compounds. They are insoluble in water and turns blue Biuret solution to purple. On the other hand, fats such as palm oil and margarine are large chemical compounds. They are insoluble in water and forms a white cloudy suspension when tested with ethanol and cold water. In this experiment, a number of foods would be tested using a series of chemical tests including the Benedict's test, Iodine test, Emulsion test and the Biuret test, to determine whether these foods contain the different macromolecules of reducing and non-reducing sugars, starch, proteins and fats. ...read more.

Middle

To another clean test tube, 2ml of cold water was added and the contents of the test tube containing the mixture of vegetable oil and ethanol was added to the test tube. In the Biuret test for protein, 2ml of egg albumen mixture was added to a clean test tube. In this test tube, 2ml of KOH (potassium hydroxide) was added followed by 2-3 drops of CuSO4 (Copper Sulphate solution). The following tests mentioned previously were completed and all observations were recorded in a table. Results: Table showing the results obtained from the tests for reducing and non-reducing sugars, starch, lipids and proteins TEST OBSERVATIONS Benedict's test Reducing Sugars Non-Reducing Sugars A colour change from blue to yellow-green and then the formation of a brick-red precipitate A colour change from blue to yellow-green and then the formation of a brick-red precipitate Starch Test-Iodine/Potassium Iodide Solution A blue-black precipitate resulted Emulsion Test/ Fat Test A cloudy white suspension was seen when the cold water was added Droplets of fat were seen floating on the surface of the emulsion Biuret Test/ Protein Test Solution turned from blue to purple Discussion: In the reducing sugars test, the solution turned from a blue colour to brick-red colour. ...read more.

Conclusion

present in the copper sulphate solution formed a complex with the nitrogen atoms that was present in the peptide bonds that held the amino acids together. The complex of the copper ions (Cu2+) and nitrogen atoms, caused the colour of CuSO4 solution from blue to purple. In the fats test, a cloudy white suspension resulted. Lipids are soluble in ethanol and insoluble in water. When the lipid was added to the ethanol, it dissolved the lipid and when it was added to the cold water, it formed a cloudy suspension which is caused by tiny droplets of lipids that are dispersed in the water. Limitations: 1. The quantity of sugar present is unknown. 2. The potato could have been oxidized due to exposure to the air. 3. The chemicals may have been left opened for too long which could affect the results. Conclusion: From the tests conducted in the experiment, reducing and non-reducing sugars were present in the food samples as the blue Benedict's solution turned to brick-red with a precipitate. Moreover, starch was also present in the food sample as the Iodine solution turned from yellow-orange to a blue-black colour with a precipitate. Protein was present in the food sample as the blue Biuret solution turned to purple. Conclusively, fat was present in the food sample as a white cloudy suspension resulted when ethanol and cold water was added. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work