BIOLOGY IA
Research question:
If the milk is unsealed does it really affect the spoilage of the milk?
Introduction and background information:
In this experiment I will see if there is a difference in the spoilage of cow milk if the milk is sealed or
not. Milk is a very popular beverage around the world over the past few years, every about 500
millions metric tons of milk was produced around the world, Sweden being even one of the top
consumer in 2013 by consuming 341,23 (kg/capita/year). But why is milk so popular and what is so
great about milk. Milk is incredibly nutritive drink is an excellent source of vitamins, it provides
potassium, calcium and vitamin D, it is also a good source of phosphorus and vitamin A lastly it also
brings a lot of protein and it contain a hundreds of different fatty acids like Oleic acid. We know that
the spoilage of milk is caused by a fermentative growth of bacteria caused by the storage
temperature, but we don’t know if the sealing of milk is really affecting it’s spoilage. We also know
that the base Ph of milk is between 6.7 to 6.9 when it starts to go under 6.7 it gets spoiled the milk
gets more acidic and the pH gets lower. I am going to conduct this experiment for 6 days because it is
the approximate time that milk gets spoiled if refrigerated. We also know that milk at room
temperature get bacteria’s in approximately two hours so I think there is going to be some results.
But why choose cow milk on top human milk, firstly because of production cow milk is a lot easier to
produce then human milk and secondly it has for most people better taste but if we only considered
the nutrition part we absorb better the nutrition of our own milk then the others.
Which brings us to another question, milk is good but all my life I was always told to seal milk
correctly or it will spoil and to test that statement and to test the hypothesis that if milk is unsealed it
spoil faster than if it is sealed, so my hypothesis will be that there is a significant difference between
the unsealed and sealed samples. My experiment is going to be based on it.
https://www.healthline.com/nutrition/milk#vitamins-minerals
https://worldpopulationreview.com/country-rankings/milk-consumption-by-country
https://en.wikipedia.org/wiki/List_of_countries_by_milk_consumption_per_capita
https://www.statista.com/statistics/272003/global-annual-consumption-of-milk-by-region/
https://onlinelibrary.wiley.com/doi/10.1002/9781119237860.ch19#:~:text=Spoilage%20of%20milk
%20and%20milk%20products%20results%20from%20growth%20of,activity%20after%20the%20heat
%20treatment.
https://www.healthline.com/health/ph-of-milk#the-ph-of-milk
https://www.usdairy.com/news-articles/how-long-can-milk-sit-out
https://www.tasteofhome.com/article/milk-safety/#:~:text=How%20Long%20Does%20Milk%20Last
%20After%20Opening%3F,its%20printed%20date%2C%20if%20refrigerated.
Variables:
Independent:
The recipients that are sealed or unsealed
Dependent:
The ph-level of the milk
Controlled:
The sealed and unsealed recipients
the size of the recipients
the quantity of milk in them
the time between the test.
Uncontrolled:
pH level
Risk assessment:
Put an white coat just for hygiene, not many risks for the experiment, don’t drink the milk.
Method:
Materials-
20 ,10 ml recipients
Cow milk
Pipette
Ph-level tester
Plasticized paper
White stickers
Black pen
Table
Distilled water
A white coat
A phone to note the results of the experiment and to take pictures
Procedure-
1. Put on the coast and prepare the 20 recipients, put the white sticker on them and write a
number from 1 to 10 so that you will remember each ot them and be capable of annoting
them for the results with the S or U, which means sealed or unsealed.
2. Put 10 ml of milk in each of the recipients and then measure the pH-level of each of them for
a base number of Ph wash the analyzer between the uses with distilled water then note the
results and note them as the first and seal with the plasticized the one that have the letter S
on the recipient the put them in a corner of a room.
3. On the second day look at the at the ph level while doing the same method as the first day
unseal the one that are sealed and reseal them correctly
4. Do the same on the third day look at the ph-level and note them then don’t look at the ph
level until the six day and do the final results.
Results
Raw data:
The two tables shows the two different results that we get from the six days for unsealed and sealed
milk with their Ph level for each day where it was analyzed, so day one, day two, day three and day 6
Unsealed:
1st day 2nd day 3rd day 6th day
U.1 7.1 7.35 6.6 5.79
U.2 7.12 7.34 6.86 6.1
U.3 7.27 7.35 7.05 5.74
U.4 7.27 7.38 7.1 5.64
U.5 7.20 7.35 7.09 5.58
U.6 7.20 7.36 6.94 6.01
U.7 7.21 7.35 6.92 5.42
U.8 7.27 7.39 7.07 5.74
U.9 7.15 7.05 6.76 5.6
U.10 7.21 7.37 6.99 5.55
Sealed:
1st day 2nd day 3rd day 6th day
S.1 7.3 7.39 6.89 6.7
S.2 7.19 7.36 6.86 6.02
S.3 7.18 7.38 6.86 5.73
S.4 7.19 7.38 6.95 6.5
S.5 7.1 7.41 7.02 6.62
S.6 7.1 7.37 6.92 6.5
S.7 7.14 7.40 6.98 6.2
S.8 7.13 7.39 6.95 6.2
S.9 7.16 7.40 6.9 5.6
S.10 7.29 7.34 6.96 5.9
Visual:
The first day results shows that we can see for the first day is that all the Ph level are above
7.1 and goes to a maximum 7.3 which is the exact same between the unsealed and sealed
results, it is normal because the experiment just started and we are on a base level where
every sample is supposed to be similar, the physical appearance is still a normal pearl white.
The second day results shows that the Ph level has gone up for the unsealed almost every
sample is above 7.3, a part from the 9 th sample which is the only one that got a 7.05 Ph level,
a part from this one the minimum is 7.34 and the maximum is 7.39 which shows that Ph-level
for most of them has gone up. We can see that the result is still pretty similar for the sealed
results, even though we can see that the maximum is a bit higher a 7.41 the result are still
looking the same with it going 7.3 to 7.4 for both of them. The physical appearance didn’t
really changed and it still looks like normal milk.
The third day results shows that the Ph level had really gone down from being a average 7.3
to 7.4 to even results as 6.6, we can see that even the result inside one of the categories is
very diverse compared to the previous days were the results were similar in the same
category this time in the unsealed one the result can go from a Ph level 6.6 to 6.7 to a result
of 7.1. For the sealed category that results are very less diverse the almost all go for a Ph
level 6.9 to 7 the minimum that is 6.86 but if we compare to the result of the unsealed
category, they are both not that different, the only real difference is that they are really less
diverse in the same category. The physical appearance this time did change a bit we can see
that milk got more of a yellowy color and it’s less white but it doesn’t change between the
two categories.
The last of day of results shows that the Ph-level got down as expected. When we look at the
result for the unsealed shows that average Ph-level was between 5.6 to 5.6 even though
some them go up to above 6 and 6.1, and for the sealed the results show that the results also
got don but they go up form 6 and above going from 6.1 to 6.7 even though some though of
them did go to 5.6 most of them stay close to 6. The most noticeable change was the physical
appearance we could that some of the milk got kind of in a solid form, we could see that
there was mold on top and that is for both of the categories, the physical appearance of both
them were the same.
Processed data:
Those two tables will sow the calculated mean and the standard deviation of the two
categories on each day to show the difference between the result.
Unsealed:
Unsealed milk Mean Standard Variances
deviation
1st day 7.2 0.058137767 0.00338
nd
2 day 7.329 0.094175368 0.008869
rd
3 day 6.938 0.15308821 0.023436
6th day 5.717 0.19834566 0.039341
Sealed:
Sealed milk Mean Standard deviation Variances
1st day 7.178 0.066302338 0.004396
2nd day 7.382 0.019899749 0.000396
3rd day 6.929 0.049689033 0.002469
6th day 6.197 0.36188534 0.130961
The formula to find the mean is to get the sum of one of the samples and divide it by the number of
number in the sample.
The formula to find the Standard deviation is this
: Means the Sum, in this case the sum of the sample
x : Is the value of the date
: This is the mean of the data
N: Means the number of data that we are calculating
To find if there is a a significant difference between the results during those days I am going to
perform an two-sample independent T-test with different variants . My null hypothesis would be that
there is not significant difference between the two samples throughout the days which means that
the p-value would be superior to the level of significance, and my alternative hypothesis would be
that there is a significant difference in those test throughout the days which means that my p-value is
inferior to the significance level . Our significance level is going to be = =0.05.
First day:
First Day of the ph-level of the milk
7.205
7.2
The mean of the ph-level
7.195
7.19
7.185
7.18
7.175
7.17
7.165
Unsealed Sealed
The Unsealed or Sealed group
The results of this test is = 0.464017
Which means that for the first day the null hypothesis is accepted because the result is superior than
0.05. This result is logic because there should not be a real difference for the first day
Second day:
Second day of the ph-level of milk
7.39
The mean of the ph-level of milk
7.38
7.37
7.36
7.35
7.34
7.33
7.32
7.31
7.3
Unsealed Sealed
The unsealed or sealed group
The result of t-test is = 0.130187
Which that for the second day the null hypothesis is accepted again and that there is no real
difference between the unsealed and sealed milk
Third day:
Third day of the Ph-level of milk
6.94
the mean of the ph-level of milk
6.938
6.936
6.934
6.932
6.93
6.928
6.926
6.924
Unsealed Sealed
The unsealed or sealed group
The result of the t-test is = 0.869856
Which shows once again that the null hypothesis is accepted because the result of the t-test is
superior to the level of significance which is 0.05 which means that there is no real difference
between the two samples.
The last day:
Last day of the ph-level of milk
6.3
the mean of the ph-level of milk
6.2
6.1
6
5.9
5.8
5.7
5.6
5.5
5.4
Unsealed Sealed
The unsealed or sealed group
The result of the t-test is = 0.464017
Which shows that even on the last day the null hypothesis is accepted because the level of
significance is inferior to the result.
Conclusion:
As we could see the spoilage of milk is not affected by the fact that it is sealed or unsealed. Firstly the
physical appearance of the milk stayed the same for both of the group or sample and got to the same
points of spoilage at the same time. Secondly we could se by the result of the analysis of the ph-level
that both group had a similar ph-level throughout the experiment, they both fell under the limit of
spoilage which is 6.7 at approximately the same time and stayed at the same level throughout the
experiment, which shows that the spoilage was not affected by the fact that it was sealed or not . So
the hypothesis that the spoilage of milk is affected by the fact that’s sealed or unsealed is wrong.
https://www.mediray.co.nz/media/15606/ds_hanna_ph_ha-hi99162_1p0_0415.pdf
https://www.healthline.com/health/ph-of-milk#the-ph-of-milk
Evaluation:
The first weakness of my experiment is maybe that I could have find better milk because we can see
that the milk that I chose had a base level of ph of 7.2 but the normal ph level is supposed to be
between 6.7 to 6.9, it may have affected my results.
The second weakness that I could find in y experiment is the fact that I couldn’t go analyze the milk
everyday it probably wouldn’t have changed the final results but I could have maybe saw more
difference in throughout the days before the complete spoilage and maybe have more difference in
my results.
Lastly my last weakness could be that my seals weren’t good enough and that I didn’t change them, I
should have maybe have got it double plasticized instead of only putting one layer and maybe
throughout the days I should have changed the plasticized paper because time would have maybe
affect their quality.
