Identification of Food Constituents Essay

mode (testing for wilducing sugars) 1. Add 3cm? of whole milk, by using a pipet or syringe to the test tube. 2. Add 5cm? of Benedicts reagent and blot it in the boiling water bathing tub for 8 minutes. Do the kindred for semi-skimmed milk and skimmed milk. 3. Once each(prenominal) 3 of the test tubes are left to cool in the air, observe the works. It will be a good idea to set up a range of act upon standards from glucose tautnesss of 1%, 2%, 3%, 4% and 5% so that you send away relate the colours observed to these concentrations. 4. A positive result would be from thousand to yellow to brick-red colour. rule (testing for non- cut sugars) 5. Make up the same stem as step 1 but this time, adding 3cm? of dilute hydrochloric acid to come off the glycosidic bonds between the monosaccharides. 6. Then add 3cm? of sodium hydroxide solution to annul 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 turn br ick-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 tried and leaving for 30 minutes at room 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 distributively of the three types of milk, just add a a few(prenominal) drops of iodine which is dissolved in potassium 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 different types of milks on apiece tube. 13. Then add 2cm? of Biuret reagent and you should see a purple-violet colour developing.The intensity of it is proportionate to the protein content. Method (testing for fats) 14. Add 3cm? of the three different types of milk on individually test tube and 3cm? of water. 15. Place 1 drop of Sudan III to each te st 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 at that place is a unambiguous stain for a positive result. Results table Solution (Milk)TestObservationsConclusionSkimmedBenedictsLime cat valium (lightest)A discount amount of monosaccharides or reducing sugars face up Semi-skimmedBenedictsLime green (lighter)A slight amount of monosaccharides or reducing sugars symbolize 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 purpleProtein present Conclusion If thither 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 settle formed when adding the Benedicts reagent. But according to my range of colour standards from glucose (monosaccharide) concentrations, the lime-green colour given out from each of the 3 milks fork ups us that it does occupy a minor amount of monosaccharides (reducing sugars).Adding a drop of invertase normally should break the glycosidic bonds that are holding the disaccharides together to form monosaccharides. But my results show that its a yellowish-green colour instead of a brick-red colour later on adding Benedicts reagent. This shows us that there is hardly any disaccharides present which I thought there would be as lactose, a disaccharide, is broadly present in milks. But this result may have a different view on that. The fact that all 3 milks cancelled purple after adding Biuret reagent assures u s that 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 marked that I havent done the test for starch and fats. This is scarce due to the fact that I run out of time. Using a 5cm? micro syringe would be more accurate than a pipette. When a precipitate is settled, I could have used a ruler to government note it out (in mm) instead of just using my eyes. Even better, using tintometer 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.