Fats 9g
Of which is saturated 6g
Sodium -0.1g
Vitamin B12
Calcium 289mg
This is for a sample of milk 250ml that is full fat milk. Milk is made up of 88% of water, tiny globules of fat float in it which is what makes it an opaque rather than transparent liquid. The fats are mostly triglycerides which provide a source of energy for the suckling infant. The kinds of fatty acids in the triglycerides vary according to the diet of the mother. Milk also contains the disaccharide lactose which , like fats provides energy. Lactose is also used within the infants body to make the monosaccharide galactose. Several proteins are found in milk , there are also various minerals especially calcium.
The constituents found in sun flower oil is - fats – 99g
Of which are saturated 11g
Of which are polyunsaturated 63.0g
Also high levels vitamin E
Method
Firstly the two solution were taken and this was the milk and the sunflower oil, a teet pipete was used for dropping a couple of drops of both the milk and the vegetable oil were dropped on to the filter paper to test for the lipids present, if there was a lipid present it should have gone translucent. Each section was labelled on the filter paper and then it was left to dry before the results were deduced from this.
Then there were four test tubes that were taken and labelled , two contained milk and two contained sunflower oil.
In each of the test tubes 2cm³ of each of the solutions was put in, this was measured using a syringe. So there was two test tubes of milk that had 2cm³ in them and two test tubes of sunflower oil that also contained 2cm³ of it in each test tube.
The second test done was the test for proteins for this to each of the test tube of milk and sunflower oil 5 drops of Biuret solution was added to it and then was left to allow the test to work. If there was protein present in either of the test tubes than that test tube should have turned purple in colour.
The second test that was then done was for the second test for lipids. This was that the test tubes that each had 2cm³ of milk and sunflower oil in them, were taken.
To these test tubes a further 2cm³ of absolute ethanol was added to the solution. It was then shaken vigorously to dissolve the lipid.
Then to each test tube of milk and sunflower oil an equal amount of water was also added to it and this was then left. If a lipid was present in either solution a white cloudy suspension should appear.
Results
Conclusion
From my results I could deduce whether or not protein or lipids were present in each of the solutions.
For the milk I came to the conclusion that there was both lipids and protein that was present in it. The reason why this was so , was because I knew that protein was present because it in the Biuret solution test turned a cloudy purple precipitate colour which indicated to me that protein was present in the milk. The reason why there is this colour change is because in because of the nitrogen atoms in the Biuret solution present in the peptide chain form a purple complex ( the nitrogen) with the Cu ²+ ions, it is the dilute copper sulphate that is in an alkaline solution.
For the milk as well as there being protein present there was also lipids that were present. The reason why I know this to be the case is because when the emulsion test was done on it , produced a cloudy white suspension which indicated to me that lipids were present in milk, the reason why this is because lipids are immiscible when they are in water. So when water is added to a solution of the lipid in alcohol results in an emulsion of tiny lipid droplets which are in the water reflect light and so therefore give a white , opalescent appearance .Triglycerides like all lipids are insoluble in water.
Also the other test for lipids further aided my results and this was the translucent test, when the drops of milk dried it produced a translucent mark which also indicated to me that this was a positive result for a lipid to form. The reason why this is , is because of the oils in the triglyceride chains causes this translucent effect on the filter paper.
For the sunflower oil I deduced from my results that it only contained lipids. This is because the test for protein turned out to be negative as there was no purple precipitate colour only a transparent blue colour at the top separated by a gel like cloudy solution at the top. So from this test I knew that there was no protein present. However when the test for lipids was done they both proved to be positive. The emulsion test produced a white cloudy suspension which was what I was expecting to see if there were lipids present, this indicated to me that there were lipids present, the reason why this happened was because lipids are immiscible when they are in water. So when water is added to a solution of the lipid in alcohol results in an emulsion of tiny lipid droplets which are in the water reflect light and so therefore give a white , opalescent appearance. Triglycerides like all lipids are insoluble in water.
Also the second test for the translucent test for lipids furthered aided my results and this produced a positive result as when the sunflower oil dried it left a translucent mark from where it had been, this indicated to me that lipids were present.
Evaluation
From my results there were a good set of results, problems with the experiment were :
- For the test for protein when adding the Biuret solution it could have been easy to mistake the colours that appeared in the test tube, however this was why more drops were added if in doubt about the colour.
- For the translucent test it was clear when a lipid was present as there was a translucent mark left however a translucent mark could have been mistaken for a not so translucent mark and may have looked at it when the filter paper was not quite dry. However this seemed to work accurately overall
- For the test for the emulsion for the lipids this could have proved difficult to tell whether the milk produced a cloudy white suspension as the colour of milk is cloudy white to start with.
- When comparing the solutions there should have been the same volume in each test tube , if there was not this meant that there was not the same concentration of lipids or protein present in it. Ways to ensure the same amount if volume in each test tube is with careful measurement when adding the biuret solution or the absolute ethanol.
- Also when analysing the colour of the test tubes it was easy to make an error to differentiate between the colour of purple or blue for the biuret test
However if I was to do this experiment again I would make the following improvements;
- Must make that it has accurate amount of volume in each test tube so that there is the same concentration of proteins / lipids in each solution so that the test is a reliable one
- Add more drops from the Buiret solution when testing for the protein to ensure a correct colour change
- Allow the filter paper to completely dry before checking if it was translucent hold it up to the light to check this
- For the emulsion test to tell with the milk whether or not is was a cloudy suspension must hold it up to the light to se if it is cloudy white suspension was present.
- A more accurate way of comparing colours other than the human eye is by using a colorimeter (automated piece of equipment that gives accurate results which would be more reliable)
The results for using a Benedict's test in milk is that , milk contains the disaccharide lactose which , like fats provides energy. Lactose is also used within the infants body to make the monosaccharide galactose. Lactose is a disaccharide therefore it is a non reducing sugar when the benedict's test is firstly done on it will have no effect first of all , however when the solution is then boiled in acid and then Benedict's is tested on it will produce a green then to orange precipitate. The reason why this is because when the benedict’s test was done for the non reducing sugar the lactose it at first had no effect, then the solutions would be neutralised and then dilute hydrochloric acid would be added to them. When lactose is heated with acid you hydrolyse it into the monosaccharide that it is made up of ( for lactose this is galactose and alpha glucose). So then when it is heated with the benedict’s solution it gives you a reaction because now it can work as there are reducing sugars present that allow it to give red precipitate. The reason why test it would now go orange is because it contains non reducing sugars so when the non reducing sugar are heated it hydrolysed into twice as many monosaccharide- reducing sugars than there were of non reducing sugars
