Yogurt Part 2: Hypothesis Testing &
Writing in Biology
Note: You will need to purchase three different cups of yogurt this week.
Overview of this week's assignment: Now that you have devised a method to test the viscosity of
yogurt, you will be conducting an experiment on yogurt viscosity. Your task is to evaluate three
different types of yogurt and to determine their viscosity. The hypothesis generation portion of this la
is to some extent under your control, but you need to ask a question.
Example, if I were evaluating the melting temperatures of different fats, I would state my question in a
way that evidence can be collected to support or disprove the hypothesis. If I have three types of fat
(butter, coconut oil and palm oil) I could ask:
"Does the percentage of saturated fat affect melting point?"
I would then make a prediction / state a hypothesis that could be tested.
"I predict that the higher the percentage of saturated fat in each substance, the higher the
melting point."
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That is a testable hypothesis. I would then heat each of the fats and make a determination about
when they melted and whether they melted in the predicted order based on saturated fat.
Scope of your yougurt experiment: You need to acquire three cups of yogurt that differ in as few
aspects of their composition as possible. Example: You could find three cups of the same
and of
plain yogurt made with skim, low-fat and whole milk and make a hypothesis about their viscosity that
is testable. Other variables that you could investigate: cow's milk yogurt vs plant-based yogurt (you
can find soy milk yogurt, almond milk yogurt, coconut milk yogurt). You can investigate different
"styles" of yogurt: Greek and Icelandic yogurt styles are popular. How do these differ in thei
preparation? I am sure there are other variables you can find to evaluate.
Once you have decided what variable you will test, you need to make a hypothesis about viscosity.
This needs to be an evidence-based hypothesis. If you're comparing Greek and regular yogurt,
investigate the scientific literature for how those types of yogurt are made.
Background research: You will need to find TWO primary scientific sources that help you devise
your hypothesis. [Hint: Look at the references in the paper you read for Lab #3 and go from there].
You will include these two sources in your assignment for the week. They should be directly related
to your hypothesis. Here is the li
ary guide to finding primary, peer-reviewed sources:
Click here to learn how to search for scientific research papers.
(https:
libguides.pvcc.edu/search-pqbio)
During this week you will need to prepare for and conduct your yogurt viscosity test. You will write
about your experiment using data that you generate this week. You have already written most of you
methods from the earlier assignment, and you will just need to add in the information about the
additional yogurts.
Finally, you will make another table that includes the data from this expanded experiment and also
include a bar graph that reports the data in graphical form. You will write a few sentences
summarizing what you found and whether the data support your hypothesis or refute it.
https:
libguides.pvcc.edu/search-pqbio
Writing in Biology
Some useful links to help with writing:
PVCC How to write a Bio Lab Report (https:
libguides.pvcc.edu
io-lab-report)
University of Richmond - Lab Report Guidelines
(http:
writing2.richmond.edu/training/project
iology/intro.html)
Introduction: Begin constructing an introduction: for this course, your introduction should be one
well-developed paragraph that ends with your hypothesis.
Methods: In the previous lab when you devised your method for testing the yogurt, you wrote a short
methods section. You will need to revise that methods section (incorporating comments you
eceived on that assignment) and write a slightly expanded methods section where you include the
types of yogurt you tested and how many times you tested each. It should still be pretty short.
Partial Results Section (Tables and Graphs): Next you will need to tabulate your results and create
a table and graph showing your data. You made a table in Lab #3, and you will just need to expand
on that format, making sure you include columns for all three of the yogurt types. You will also be
including a bar graph of your results - made with a graphing / spreadsheet program like Excel o
Google sheets. Here is a video about how to create a simple bar graph in Google Sheets:
Graphing Video (https:
youtu.be/-x_mBMkB9KQ)
(https:
youtu.be/-x_mBMkB9KQ)
Summary: We will not be doing a fully separate results and discussion section for this lab, but you
should write a
ief overview of your findings. Explain what your data show (yogurt A was thicke
than B and C according to your data) and then whether this matched your hypothesis. If it did support
your hypothesis: make a clear statement about what variable seems to be affecting thickness. If you
data did NOT support your hypothesis, explain what might be going on. Again, this should be no
more than 200 words or so.
Example of a summary : The almond milk had a longer average time to drip through the cheese cloth
(57 seconds) than did either of the dairy milk yogurts (32 seconds for skim milk yogurt and 45
seconds for whole milk yogurt) . This suggests that the almond milk yogurt was thicker than both the
whole milk yogurt and the skim milk yogurt, which was contrary to my predictions. This is likely
ecause additional chemical stabilizers like guar gum were added to the almond milk yogurt so that it
would hold together since it lacks casein protein which helps dairy yogurt thicken. The amount of fat
https:
libguides.pvcc.edu
io-lab-report
http:
writing2.richmond.edu/training/project
iology/intro.html
https:
youtu.be/-x_mBMkB9KQ
https:
youtu.be/-x_mBMkB9KQ
in the almond milk was also higher than both the whole milk and skim milk yogurts, and this could
also have had an effect.
Preview of Questions on Post-Lab Quiz
The post-lab quiz will ask for the following content. Please take a look at the questions so you know
exactly what you will need to post/upload.
Question 1
Background Research: Primary Source #1 & Single sentence summary of why it's relevant to you
hypothesis (in your own words)
Include primary source #1 that is relevant to your yogurt hypothesis and experiment. Write in APA
Format:
Yaakob, H., Ahmed, N.R., Daud, S.K. et al. Optimization of ingredient and processing levels for the
production of coconut yogurt using response surface methodology. Food Sci Biotechnol 21, 933–940
XXXXXXXXXXhttps:
doi.org/10.1007/s XXXXXXXXXX
Summary in your own words: This is relevant to my hypothesis because it discusses the optimal
conditions (pH, temperature) for producing coconut milk yogurt and getting it to a desired thickness.
Question 2
Background Research: Primary Source #2 & Single sentence summary of why it's relevant to you
hypothesis (in your own words)
Include primary source #2 that is relevant to your yogurt hypothesis and experiment. Write in APA
Format:
Yaakob, H., Ahmed, N.R., Daud, S.K. et al. Optimization of ingredient and processing levels for the
production of coconut yogurt using response surface methodology. Food Sci Biotechnol 21, 933–940
XXXXXXXXXXhttps:
doi.org/10.1007/s XXXXXXXXXX
Summary in your own words: This is relevant to my hypothesis because it discusses the optimal
conditions (pH, temperature) for producing coconut milk yogurt and getting it to a desired thickness.
Question 3
Write a short (2-3 sentences) background for your study. What are you researching? Why do you
think you might see a difference in thickness of the yogurt? End with a clear, single sentence,
testable hypothesis for your yogurt experiment.
Example:
Citrus fruit like oranges contain high concentrations of citric acid. possibly to deter seed predators.
Different types of citrus fruits vary in their citric acid concentrations. I predict that lemon juice is more
acidic than orange juice and that orange juice is more acidic than water.
Question 4
Write your new (revised) methods for this experiment that include the types of yogurt tested and the
number of replicates (times) you tested each sample.
Question 5
Please upload a picture of your yogurt-testing set-up. This can be the materials assembled, or the
test in action. (I recognize some of the tests are so fast that it will be hard to get a picture while also
ecording data).
Please upload the picture as a pdf, jpeg, png or gif (embedded in a word document is ok too)
Question 6
Upload your Results table . Make sure you have labeled your table clearly with an appropriate title.
(Please upload as a word document or PDF if possible)
Question 7
Upload your bar graph of the average data from your experiment. Make sure all axes are labeled and
there is a clear title for the graph. Please submit as a Word document or PDF.
Question 8
Write your summary of your findings here. It should be no more than one paragraph (4-5 sentences)
and should explain what you found and whether your data support your initial hypothesis. (Paste the
text into the text box)