First Experiment: how do emulsifiers and stablizers affect the stailization of vinaigrette emulsion?
First experiment: To
investigate the effects of emulsifiers and stabilizers to the stability of
vinaigrette emulsion
Date: 21/03/2020 Saturday
Question: how would the quantity of emulsifiers and stabilizers
affect the rate of coalescence of vinaigrette?
1. Introduction and
background information
It all starts with the simple question: what does ‘good’
vinaigrette mean? Having appeared more than 1000 years ago, the oil-and-vinegar
concoction has won the hearts of many. Yet strange enough, the polar vinegar
and non-polar vinegar are not meant to be with each other – if you put it in a
jar, then they will eventually separate. Being well aware of the importance of
forming emulsion, still, along with other cooking newbies, I thought it is all
about shaking hard before serving. Unsurprisingly, no matter how hard I shook, such
unstable vinaigrette eventually separates within minutes. The salad served with
it would then, ‘mysteriously’, will and be flavorless.
Figure 1: how oil damages sald (something we all don't want right XP)
Turns out the oil would damage the greens by penetrating
the waxy cuticle of the leaves, they thus will. The vinegar would also slide
down, leading to a flavorless salad. This phenomenon hence enlightens me, how
can I serve a delicious salad? Is there a magical ingredient that bonds the oil
and the vinegar together? If yes, how much should I add to keep the emulsion
while not affecting the original taste?
1.1 Aim of the
experiment
Followed by the previous questions, in the following
experiment, it is expected to investigate how the amount of two commonly used
emulsifiers, mayonnaise and mustard, as well as one stabilizer, molasses, would
affect the stabilization of the oil-and-vinegar emulsion.
1.2 Hypothesis
The more emulsifieror stabilizer added, the more stabilized
the emulsion. However, for stabilizers, after reaching an optimum amount, the
more added, the less stable the emulsion.
1.3 Prediction:
For mustard and mayonnaise, the emulsion will be
increasingly stable. The ranking of separation time needed for the respective
vinaigrette in descending order would be the vinaigrette with the
emulsifier-to-emulsion ratio 1:3 > 1:4 > 1:5 > 1:6. So most amount of
time will be needed when 10g of emulsifier is added to 30g of oil and vinegar.
However, for honey, the separation time may increase when more
is added, and then decrease. Such turning point might occur when the
honey-to-emulsion ratio is 1:5, which means when 7.5g honey is added to 30g of
oil and vinegar.
1.4 Scientific
principle behind vinaigrette
An emulsion is a mixture of two immiscible liquids in which
one liquid is dispersed as spherical droplets into the continuous phase,
forming a homogenous mixture. In vinaigrette, water is in dispersedphase, while
oil is the continuous phase, so it is a water-in-oil emulsion.
Why don't oil and water mix together? In fact, oil is a
non-polar compound,as electrons are evenly distributed across each lipid
molecule. However, vinegar is a polar compound, as it contains acetic acid and
water molecules due to the uneven share of electrons between the atoms of the
two kinds of molecules. Following the like dissolves like chemistry principle, polar
molecules interact with other polar molecules. The same works with non-polar
molecules. No hard feelings, but this is like why it's so hard for us to make true friends. Apparently only those carrying the same qualities as you do can truly connect with you.
Figure 2a): molecules in vinegar (acetic acid and water)
Figure 2b): lipid molecules
Also, as the water molecules are more mobile than the fat
molecules, the former will force the latter to join into larger and larger droplets,
leading to coalescence eventually phase inversion (or phase separation),
separate into two layers according to their respective densities. In
vinaigrette, vinegar sits on the bottom as it is denser.
Figure 3: Sendimentation, flocculation and coalescence
Figure 4: Less dense oil comes on top
To prevent phase separation, either emulsifier or
stabilizer could be added to decrease the interfacial tension between the
dispersed and continuous phase, to reduce the rate of smaller droplets joining
to larger ones and form stable micelles. Here, for emulsifiers, mustard contains mucilage and
polysaccaride, which is a glutinous substance that contains protein and
polysaccharides. Egg yolk in mayonnaise also contains lecithin, in addition to
protein.
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| Figure 5: when will coalesnce occur and how to form micelles |
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| Figure 6: closer look to emulsifiers |
Lecithin and polysaccharide are surfactants and hybrid
compounds. They containsmolecules with a hydrophilic (water loving) head and a
hydrophobic (water hating) tail. Its head attracts water, while its tail
attracts oil. It thus acts as a bridge holding the two immiscible liquids together,
and micelles will form. For amino acid chains composing protein molecules, they
also have the two receptors, linking oil and water together.
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| Figure 7: difference between emulsifiers and stabilizers |
Apart from being an emulsifier, protein and mucilage can
also be a stabilizer. Honey could be an example as well. Because the molecules
are extremely large, the two increase the viscosity of the vinaigrette and give
a thicker texture to the continuous phase (vinegar).It thus becomes difficult
for the oil droplets to mobilize and coalesce into larger droplets, and
eventually separate from the water. Thus, the rate of separation is slowed
down.
2. Experiment details
2.1 How to nail down the range of independent variable
After ploughing into a wide range of basic balsamic vinaigrette recipe (whether from cook illustrated, serious eats, or newspapers like New York Times and Time Colonist, it was found that while mustard seems to be the necessary emulsifier, honey is the relatively common one and mayo is not. Also, they are all added in small quantity. The ratio of emulsifier to oil-and-vinegar ratio is usually 1:10 or lower.
Until I read about Cook Illustrated's article regarding the make-ahead vinaigrette which lasts for so long relying on the three emulsifiers. It thus enlighted me what would be the optimum quantity for each of the three, in order to make a long-lasting vinaigrette. Originally, I tried to maximise it to 1:1. However, as shown in the video, the viscosity of mustard was so large that the whole sauce has turned into mustard. Thus I decided to reduce the ratio a bit. Thus, I decided to vary the amount from 1:3 to 1:6, to maximise the emulsifying ability of the three.
2.1 How to nail down the range of independent variable
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| Figure 8: Science & Food: 12.5g (mustard + garlic) / 177g =1:14 |
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| Figure 8: Serious Eats: 20g / 222g (vinegar + oil) = 1:11 |
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| Figure 9: Times Colonist: 40g (Dijon mustard + honey + garlic) / 255g (vinegar + oil) = 1:8 |
Video 1: not-so-good first trial using the origial ratios of 1:1, 1:3 and 1:5
After ploughing into a wide range of basic balsamic vinaigrette recipe (whether from cook illustrated, serious eats, or newspapers like New York Times and Time Colonist, it was found that while mustard seems to be the necessary emulsifier, honey is the relatively common one and mayo is not. Also, they are all added in small quantity. The ratio of emulsifier to oil-and-vinegar ratio is usually 1:10 or lower.
Until I read about Cook Illustrated's article regarding the make-ahead vinaigrette which lasts for so long relying on the three emulsifiers. It thus enlighted me what would be the optimum quantity for each of the three, in order to make a long-lasting vinaigrette. Originally, I tried to maximise it to 1:1. However, as shown in the video, the viscosity of mustard was so large that the whole sauce has turned into mustard. Thus I decided to reduce the ratio a bit. Thus, I decided to vary the amount from 1:3 to 1:6, to maximise the emulsifying ability of the three.
2.2 Three Independents
Independent
Variable
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Ratio of the emulsifier/stabilizer to the water-in-oil
emulsion. (1:3, 1:4, 1:5 and 1:6)
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Method of changing independent variable
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Changing the amount of emulsifiers/stabilizers added to
the emulsion.
For 1:3 ratio, add 10g.
For 1:4 ratio, add 7.5g.
For 1:5 ratio, add 6g.
For 1:6 ratio, add 5g
|
Control group
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Conduct the same experiment by using a vinaigrette
without mustard, mayonnaise and molasses as control group
|
Dependent
variable
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The separation time of the vinaigrette emulsion
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Method of measuring dependent variable
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1. Measure the height (cm) from the middle of the bottom
of the jar to the center of the meniscus of acid layer before mixing, and
every 5 minutes after mixing until reaching 35 minutes.
2. Calculate the difference of the initial and ending
height of the boundaries of the vinaigrettes.
3. The larger the ending difference (at 35 minutes), the
longer time it takes for the vinaigrette to separate. If the difference is overlapping,
then trace back to the time slot when there is no overlapping, and compare
the values, with the larger difference being the more stabilized one.
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How to make sure the accuracy of the dependent variable
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1. Measure
the height of the acid layer twiceand calculate the average value as the
final result.
2. Measure
by putting the tape at the same position (vertically on the table).
3. Take
the measurement from the center of the meniscus of acid layer.
4. Read
the value horizontally.
5. Reduce
all the height by 2mm to remove the discrepancy brought by the thickness of the
jar.
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Controlled variable
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1. The
quantity of other ingredients (Balsamic vinegar, olive oil, canola oil,
garlic powder, salt and pepper)
2. The
types and brands of other ingredients (Balsamic vinegar, olive oil, canola
oil, garlic powder, salt and pepper)
3. The
whisking time and method for every experimental group (15 times with
up-and-down motion counted as one time, around 5 seconds)
4. The
preparation and storage temperature (25°C)
5. The
container used (closed glass jar)
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How to control
the consistency of controlled variable
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1. For
the temperature, we will put all the jars on the kitchen table to ensure the
consistency of the preparation and storage temperature.
2. For
whisking time and method, we will start shaking at the same time, shaking
with 15 times and shaking for 5 seconds.
|
2.2 Five 'W's about the
experiment
Who: Me,
Ye Yihan (UID: 3035705104) and my parents
What: To
investigate effect of the amount of different emulsifiers and stabilizers on
the stabilization of vinaigrette emulsion
Where:
Kitchen, home
 |
| Figure 10: what is the height of the boundary and when it would occur |
When: Carry out the measurement of the height of the boundary (acid layer) after making vinaigrettes with different types and amount of emulsifiers and stabilizers.
Why: To
find out the optimum amount of emulsifiers and stabilizers for the vinaigrette
that stays the longest.
2.3 Precautions:
1. Always
remember to label the jars to avoid confusion.
Ingredients
Balsamic vinegar 500ml
|
Wet market
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olive oil 500ml
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Supermarket
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canola oil 500ml
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Supermarket
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garlic powder 42g
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Supermarket
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Mustard 226g
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Supermarket
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Mayonnaise 250ml
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Supermarket
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Honey 500g
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Supermarket
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salt and pepper Roughly 30g each
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Wet market
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Equipment
1 Measuring
Tape
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Home
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1 Electronic
Scale
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Home
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Abandoned because of inconvenience |
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4 Identical Containers
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Home
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2 fully
charged phones
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Mine and my
mom’s
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2 Sheets of
Labels
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Stationery
shop
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1 logbook
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Home
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1 pencil and 1
rubber
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Home
|
2.4 How (Procedure):
Video 3: Squeeze instead of using plastic bag, while using spoon to adjust the quantity and ensure accuracy
1. Squeeze the mustard into the jar, until the scale shows 5g.
2. Label it with ‘5g mustard’.
3. Repeat step 1-2, measure 5g, 6g, 7.5g and 10g mustard respectively.
4. Put the four labeled jars respectively on the electronic scale and return to zero.
5. Use three different spoons to pour in the liquid, following the order of 10g vinegar, 20g olive oil, and 10g canola oil.
6. Label the one without any emulsifiers or stabilizers added with ‘control group’.
7. Measure the initial height of boundary.
Video 4: possible error of the experiment, which was caused by the inconsistent shaking force and time
8. Close the jars. My parents will shake the jars with one in each hand, and I’ll start timing with one phone and recording with another.
9. Put down the four jars on the table, and start recording time-lapse video.
10. After five minutes, use the tape to measure the height of the boundary from the middle bottom of the jar to the center of the meniscus of the acid layer. Read horizontally twice to make sure the accuracy of the data.
11. Record the two data on the data sheet.
12. Repeat step 10-11 every 5 minutes in the 30 minutes.
13. Repeat step 1-12 twice more, replacing mustard with mayonnaise and molasses.
4. Process of the four groups (recorded in time-lapse video)
3. Data Analysis
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| Figure 11: Experiment results of mustard group |
For the mustard group, when the
quantity increased from 5g to 7.5g, the higher the quantity of mustard added
(IV), the slower the boundary rose, the longer it takes for the emulsion to
separate (DV).However, when the quantity exceeded 7.5g to10g, the separation
time drastically reduced to a extremely low level, which is even lower than the
control group (without mustard).
This result indicated that, acting mainly as emulsifier,
mustard is also a quite strong stabilizer, and its stabilizing ability is
affected by the later when reaching a certain quantity, since the high
viscosity might lead to sedimentation, thus speeding up the rate of phase
separation.
 |
| Figure 12: Experiment results of mayonnaise group |
For the mayonnaise group, firstly, the
experiment results were quite unusual. The separation time of all mayonnaise
groups was shorter than the control group. Secondly, when the quantity
increased from 5g to 6g, the higher the quantity of mayonnaise added (IV), the
slower the boundary rose, the longer the separation time (DV). While increasing
from 7.5g to 10g, the higher the quantity, the quicker the boundary rose, and
the shorter the separation time (DV).
The result thus displayed that as an emulsifying agent
might not be that efficient in stabilizing when adding too much, because of its
extremely high viscosity, the surface area for the lecithin inside might be
largely reduced, as flocculation occurred. Which means, there might be little
lumps inside the vinegar formed by mayonnaise. Thus, when exceeding a certain
amount, sedimentation took place shortly after combining, thus speeding up the
rate of phase separation.
 |
| Figure 13: Experiment results of honey group |
For the honey group, the experiment results were partially
unusual too. Although there was an overall trend that the more honey added
(IV), the slower the boundary rose, and the longer the separation time (DV),
when the amount increased from 5g to 6g, the separation time was still shorter
than the control group. When the amount continued to rose to 7.5g and 10g, the
separation time seemed to be quite similar, with the group with 7.5g honey
initially more stable than the 10g group.
While for the honey, it was merely a stabilizer without any
emulsifying ability. However, its viscosity, though a lot lower than
mayonnaise, is still relatively high and allows it to maintain a level of
fluidity. Thus, flocculation and sedimentation would be less inclined than mayo
to occur when honey is combined with vinaigrette, and thus the higher the
quantity, the better the large molecules can cut the oil droplets in
vinaigrette into smaller size, and the longer the separation time.
4. Findings
With the aforementioned analysis, it could be thus
concluded that for mustard and mayonnaise, the more added, and longer the
separation time, and thus the more stabilized the vinaigrette. However, the
optimum ratio for mustard and honey to the oil-and-vinegar emulsion would be
1:4 (7.5g) and 1:5 (6g) respectively. While for honey, there seemed to be no
optimum point, both vinaigrettes having ratios of 1:3 (10g) and 1:4 (7.5g) had
strong stabilizing effect.
5. Possible errors and how to minimize them
1. Controlling the amount of oil and vinegar: when shaking
the containers, some of them were not fully sealed, thus the quantity of some
vinaigrette might be lower, leading to inconsistency of the results, such as
undermeasure the height of the boundary. It is suggested that four new
containers could be purchased.
2. Method and time of whisking: When mixing the mayonnaise
and mustard by shaking the container, some were clung to the wall, thus the
vinaigrette was not properly mixed. Also, the shaking force is inconsistent
when shaken by different people, which might affect the stability of
vinaigrette. It is proposed that the vinaigrette could be mixed in a bowl with
a whisker just by one person (say me) for one minute and pour it into the container
for observation. Different timers would be set up to avoid the time lapse
between each sample.
3. The design of the experiment as a whole: as the
experiment might consume a lot of ingredients, and as the experiment results
showed that the emulsifying effect seemed to be quite similar, and two possible reasons might suggest this finding.
First, it might be due to the large quantity added to the vinaigrette. As the common ratio would mostly be more than 1:10, the viscosity might hinder the emulsifying ability of the two emulsifiers. Thus, the amount of emulsifiers might be further reduced.
Second, it might be due to the similar stabilizing ability between the emulsifiers. Thus, a new set of experiment might be conducted next time by using this time's results, to further investigate the best combination of the emulsifier and stabilizer. This would mean having only four sets of experiment, while one is with all three added, one emits mustard, one emits mayo and one emits honey. Also, the valuation of separation time might be swapped to only measure the time it takes for the vinaigrette to separate entirely too. However, the feasibility and effectiveness of the experiment shall be further evaluated by the teacher this week and my through research.
First, it might be due to the large quantity added to the vinaigrette. As the common ratio would mostly be more than 1:10, the viscosity might hinder the emulsifying ability of the two emulsifiers. Thus, the amount of emulsifiers might be further reduced.
Second, it might be due to the similar stabilizing ability between the emulsifiers. Thus, a new set of experiment might be conducted next time by using this time's results, to further investigate the best combination of the emulsifier and stabilizer. This would mean having only four sets of experiment, while one is with all three added, one emits mustard, one emits mayo and one emits honey. Also, the valuation of separation time might be swapped to only measure the time it takes for the vinaigrette to separate entirely too. However, the feasibility and effectiveness of the experiment shall be further evaluated by the teacher this week and my through research.
Introduction and background information
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Scientific principle
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Figure 2&6: https://www.scienceandfood.org/vinaigrette/
Figure 3: https://www.bonappetit.com/test-kitchen/cooking-tips/article/become-a-better-cook-44. |
Five W’s
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