Identification of Food Constituents Essay Example for Free

Identification of Food Constituents Essay mode ( raiseing for cut down sugars) 1. Add 3cm? of whole milk, by using a pipette or syringe to the test tube. 2. Add 5cm? of Benedicts reagent and place it in the boiling water bath for 8 minutes. Do the same for semi-skimmed milk and skimmed milk. 3. Once all 3 of the test tubes argon left to change in the air, observe the colours. It will be a good idea to set up a range of colour standards from glucose concentrations of 1%, 2%, 3%, 4% and 5% so that you can push the colours observed to these concentrations. 4. A positive result would be from green to yellow to brick-red colour.Method (testing for non-reducing sugars) 5. watch up the same solution as step 1 but this time, adding 3cm? of dilute hydrochloric acid to amend the glycosidic bonds between the monosaccharides. 6. Then add 3cm? of sodium hydroxide solution to neutralise it. 7. Add 5cm? of Benedicts reagent and place it in the water bath for 8 minutes. 8. Once its left to cool, it should now unfreeze brick-red colour. 9. The concentration of a non-reducing sugar can be estimated by first adding a drop of 10% invertase (sucrase) concentrate to 2cm?of the solution to be tested and leaving for 30 minutes at path temperature. The solution is tested for the presence of a reducing sugar. This method is preferable to acid hydrolysis. Method (testing for starch) 10. On apiece of the 3 types of milk, just add a few drops of iodine which is dissolved in grand iodide solution. 11. The sample should change from browny-orange, to a dark, blue-black colour. Method (testing for proteins) 12. Place 2cm? of the three diametrical types of milks on all(prenominal) tube. 13. Then add 2cm? of Biuret reagent and you should see a purple-violet colour developing.The intensity of it is proportional to the protein content. Method (testing for fats) 14. Add 3cm? of the three different types of milk on each test tube and 3cm? of water. 15. Place 1 drop of Sudan collar to each test tube and shake gently to mix. 16. Using a microscope, a slide and a cover slip, identify any emulsion of red fat droplets. 17. Alternatively, you could add a drop of each of the milk on a filter paper and see if in that location is a translucent crap for a positive result. Results table Solution (Milk)TestObservations closeSkimmedBenedictsLime green (lightest)A splendid amount of monosaccharides or reducing sugars present Semi-skimmedBenedictsLime green (lighter)A slight amount of monosaccharides or reducing sugars present WholeBenedictsLime greenA slight amount of monosaccharides or reducing sugars present SkimmedInvertaseYellowish-greenHardly any monosaccharides or reducing sugars present Semi-skimmedInvertaseYellowish-greenHardly any monosaccharides or reducing sugars present WholeInvertaseYellowish-greenHardly any monosaccharides or reducing sugars present SkimmedBiuretViolet purpleProtein present.Semi-skimmedBiuretPurpleLots of protein present WholeBiuretLight p urpleProtein present Conclusion If there were to be a fair amount of monosaccharides to be present all 3 different types of milk, then we would surely see a brick-red precipitate formed when adding the Benedicts reagent. But consort to my range of colour standards from glucose (monosaccharide) concentrations, the lime-green colour given out from each of the 3 milks shows us that it does contain a minor amount of monosaccharides (reducing sugars).Adding a drop of invertase normally should break the glycosidic bonds that are holding the disaccharides unneurotic to form monosaccharides. But my results show that its a yellowish-green colour instead of a brick-red colour by and by adding Benedicts reagent. This shows us that there is hardly any disaccharides present which I thought there would be as lactose, a disaccharide, is mostly present in milks. But this result may ache a different view on that. The fact that all 3 milks turned purple later adding Biuret reagent assures us tha t there is protein present.If there is protein present, that means there is starch present too because starch and proteins are polysaccharides. Evaluation It is noticeable that I havent done the test for starch and fats. This is simply payable to the fact that I run out of time. Using a 5cm? micro syringe would be to a greater extent right than a pipette. When a precipitate is settled, I could have used a ruler to appreciate it out (in mm) instead of just using my eyes. Even better, using colorimeter would have provide accurate measurements on the amount of colour present and therefore, give us an indication of how much of the food constituents were present.