The final and most significant change we made to the experiment was the method we used to investigate the lipid content of the milk. We changed this procedure totally, as we believed that the new, improved method would provide us with much more accurate results than the previous one. So the method we used for testing for lipids was as follows:
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Add 5 cm3 of milk to a test tube.
- Add an equal amount of Sudan III solution.
- Shake the solution for 1 minute approx.
- Allow to settle.
The expected result is that the fats should rise to the top and then the idea was to measure the depth of the red layer.
Other than these changes we followed the suggested procedures exactly. Although our results were not as we expected.
Results:
Conclusion:
The initial aim of this investigation was to identify whether or not the processing of milk affects its nutritional content. However, the results obtained were not very accurate and furthermore, it is difficult to interpret qualitative data rather than quantitative data. Due to this lack of accurate results it is difficult to make any logical conclusions from the data. We can make some conclusions from the results we obtained, but in order to be entirely certain that these conclusions were accurate we would have to repeat the procedure, using an improved method.
Although our test for reducing sugars was not successful, the results should have been that the solution turned brick red, the reason we could not obtain these results may have been due to many factors, but it is likely to be because we did not leave the solution in the water bath for long enough, along with the fact that milk generally does not have a high percentage of sugar content anyway.
It is both clear and logical to make the conclusion that the processing of milk does affect its nutritional content to some extent. Although there is not much difference between the results for UHT whole milk and whole milk, it is clear that skimmed milk has quite a different nutritional content to the other two. Skimmed milk is designed to be less fattening and thus have a lower lipid content – according to my results this lower lipid content is made up by the higher content of protein in the skimmed milk sample.
Below I have recorded some information from the packaging of the milk, this enables me to see the results that my experiments should have indicated.
Analysis of Samples:
Reducing Sugar Content (Benedicts Test):
Lipid Content (Sudan III Test):
Protein Content (Biuret Test):
This nutritional information indicates to me that skimmed milk contains the most reducing sugars, and that whole and UHT milk have approximately the same amount. Furthermore, they indicate that skimmed milk has a very low amount of lipids in comparison to the other two types of milk. In fact the only food constituent that skimmed milk has a higher content of is proteins. Although, it does evoke the idea that overall there really is not that much alteration of this food constituent between the milks that we have tested. UHT milk and whole milk have very similar amounts in the food constituents tested for, and skimmed milk is the only type of milk that there are significant differences in. This leads me to draw the conclusion that some processing does affect the food constituents significantly, whereas others don’t. Skimming of the milk makes quite a different to the nutritional value, but the UHT process doesn’t really alter the milk content very much. This is logical, as skimmed milk is often thought of as the ‘healthier alternative’, and so these results were as could be expected.
Evaluation:
My results are not as accurate as I would have liked them to be, this could be due to many factors. Overall, my results indicate to me that the method I used to conduct the experiment was not a very good one. There were several things as I noticed as I carried out my experiment, and also factors that I would change if I were to re do the procedure.
The first thing I would change is that I would try to find more accurate measuring techniques, it was difficult to be sure that the measurements were accurate when using syringes. There were often bubbles in the syringe which also made it harder to ensure the measurements were accurate. This lack of accuracy is likely to have affected the results, and therefore by making it more accurate, the results obtained would be much more accurate.
I would also ensure that I cleaned the syringe more thoroughly when transferring liquids. If the syringe was not thoroughly cleaned then the test would be unfair and thus would lead to inaccurate results. In addition, to this I would label the test tubes more accurately, as I found myself getting confused with which test tube contained which substance.
Another alteration I would make would be to change the time the test tube was left in the water bath when testing for reducing sugars. Although we did change the procedure so that it was immersed for 15 minutes (rather than 8), the time still did not seem sufficient. When we removed the solution, the colour was not as we expected, and this was due to the fact that it was not heated for long enough. By leaving it for longer, we could be certain that the procedure was finished and that the results obtained were as accurate as possible.
Finally, I would repeat the method as many times as possible – the more times you repeat an experiment, the more accurate the results will be. By repeating the experiment, not only would it be easier to identify any anomalous results, but also I could find an overall result which is accurate as possible.
There are also ways that this investigation into the food constituents in milk could be extended. You could use the same procedures to test on different types of milk, there are so many different types of milk and each is likely to be different in it’s nutritional value. You could try testing other processed foods for different food constituents. Finally, you could test for different constituents using more food testing techniques, for example, starch or non-reducing sugars.
Miss Fox. Testing For Food Constituents In Milk
