An Experimental Study Investigating the Effect of Food Preparation on Ascorbic Acid Content in Fruits
Background Information: S. lycopersicum (tomato) is one of the most important vegetables grown for consumption in
virtually every Nigerian home. Speaking as a Nigerian, it is a common ingredient in many of our traditional meals such as
Jollof rice. This is mainly because scurvy is fairly common and S. lycopersicum has been recognized as a food rich in
ascorbic acid (Vitamin C), so is highly consumed in order to decrease risks of scurvy. Also, S. lycopersicum is one of the
most commonly grown vegetables in Nigeria and is one of the cheapest and most readily available sources of proteins and
vitamins. S. lycopersicum has great nutritional values that include controlling blood sugar through the high chromium
content, helping reduce the risk of heart attacks, strokes and cancer as they contain Vitamin B and potassium and lastly,
helping improve eyesight and strengthening bones through Vitamin A content. However, most Nigerian’s are aware that
there are some disadvantages with consuming too many tomatoes due to its high content in acid and lycopene, for
example, the slowing down of the immune system, acid reflux and Vitamin overdose.
Although S. lycopersicum is a fruit that can be consumed raw, a majority of the time, Nigerian recipes that
involve cooking with S. lycopersicum require boiling at mid to high temperatures for around 20-30 minutes. When
learning how to cook, my mother made sure to inform me that in order to maintain as much minerals and nutrients from
the ingredients, including S. lycopersicum, I would need to ensure proper storage conditions and also try to avoid boiling,
if I couldn’t I should try to minimize the preparation time with as low heat as possible. I always knew that storage
temperature and time as well preparation temperature had an impact on the nutrient content in food products, but it wasn’t
until this course that I learned the scientific reasoning behind the loss of nutrient content. I felt that the knowledge of
deterioration of fresh commodities due to water loss, temperature, ripening and physical damage was fairly common and I
wanted to gain a concrete scientific understanding on what exactly was happening. Therefore, I jumped at the opportunity
to investigate this topic for my biology internal assessment.
However, before carrying out my exploration, I had to decide what nutritional content I would be investigating. I
chose to focus specifically on the ascorbic acid content in the S. lycopersicum. I chose this because after conducting some
research on because it is one of the most popular vitamins known and I already knew a redox titration that would help
calculate the vitamin C content through the IB chemistry course. Prior to beginning my investigation, I found some
information online to give me some background knowledge of Vitamin C. I found that it is considered the only active
isomer of ascorbic acid that needs to be consumed through food and/or other supplements as the body cannot produce it
on its own. Interestingly, I gained new knowledge from my research on vitamin C, as I thought only the basic fruits like
oranges, lemons, etc. contained high vitamin C content but many vegetables like Brussel sprouts and broccoli contain
large amounts of vitamin C as well. The main reason why I chose to investigate this is because of its significant health
benefits in the human body. I learned that, it improves the condition of gums and death, strengthens the blood vessels,
helps heals wounds, regulates redox processes and most importantly, boosts the immune system (Agbemafle, 2815),
which in an environment like West Africa is very beneficial due to the many exposures to diseases such as malaria.
Through unit 1 of the course I was able to learn about
cell membranes and how they are affected by temperature. I
learned that as cellular membranes are composed of many
different proteins, such as integral proteins, that can be
denatured at high temperatures due to a change in the
interaction between certain amino acids that leads to
irreversible changes in the quaternary, tertiary and sometimes
secondary structures of the protein. Then the proteins denature
and lose their form and function. After learning this, I
wondered whether this was the same case with vitamins. In Siane, Fayle ―Redox equilibrium between ascorbic acid
order to find out, I conducted some research. I found that for a and DHA.‖ Food Chemistry, Elsevier, 2000, New York,
majority of vitamins the temperature it is exposed to has a large USA,
https://www.sciencedirect.com/science/article/pii/S03088
impact on the molecule. Specifically, I found that Vitamin C is
14600000777.
an unstable, water-soluble molecule that is vulnerable when
subjected to heat, light and oxygen. At high temperatures, Vitamin C can react and be oxidized and also can leach out, due
to denaturation of the proteins of the cell membrane, into the water and be dissolved. I chose to focus on the oxidation of
Vitamin C into dehydroascorbic acid and the dissolving as the scientific reasoning behind my predictions. Similar to what
happens with proteins, when vitamin C is oxidized it loses its form and function and therefore becomes inactive due to the
addition of oxygen and loss of hydrogen ions (Agbemafle, 2815). All of this intrigued me, as I found irony in the fact that
we try to consume as much vitamin C from S. lycopersicum as possible but end up rendering it useless through the
preparation process and so, I wanted to identify a cause and effect relationship between increasing temperature and
vitamin C content.
1
, There is a very common redox titration that is used to determine the concentration of Vitamin C and it is what I used in
my investigation. Iodine was used as a titrant and starch as an indicator to determine the concentration of vitamin C. I
used Iodine because it can only react with the starch once the ascorbic acid has completely been oxidized and therefore the
number of moles of Iodine used can determine the concentration of ascorbic acid in the sample. I used this method to
determine the effect of temperature on the vitamin C content in S. lycopersicum. I calculated this using the chemistry
titration formula 𝐶1𝑉1 = 𝐶&𝑉& this allows for me to determine the concentration of ascorbic acid (𝐶&) through the
concentration and volume of the Iodine that I used ( 𝐶1𝑉1) and the volume of the sample used (𝑉&).
I did this in order to explore the scientific reasoning behind, what I had been told previously on maintaining
nutrients in food preparation.
Research Question: How does increasing the preparation temperature (00.00℃, 20.00℃, 40.00℃, 60.00℃ and 80.00℃
±0.01℃) of 25.00 ±0.50𝑐𝑚+ Solanum lycopersicum in 100.00𝑐𝑚+ of distilled water, through cooling and boiling affect
its ascorbic acid content; measured indirectly through the volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution (𝑐𝑚+) required to turn
the 25.00𝑐𝑚+ sample blue in a redox titration reaction, using a 50.00𝑐𝑚+ burette (±0.05𝑐𝑚+)?
Variables
Table 1.1. The independent, dependent variables of my investigation
Independent The independent variable of my investigation was the temperature that the 25.00𝑐𝑚+ S. lycopersicum in
variable: 100.00𝑐𝑚+ of distilled water would be prepared in
Measured by:
I used a data harvest temperature probe with the data logger to measure the temperature. I also used an ice
bath and a hot plate to cool down and heat up the 25.00𝑐𝑚+ S. lycopersicum and distilled water sample to the
desired temperatures. The uncertainty of the temperature probe that I used in my investigation was ±0.01°C
Unit of Measurement:
I measured the temperature in degrees Celsius (°C)
Data Range:
00.00°C
20.00°C
40.00°C
60.00°C
80.00°C
Dependent The dependent variable of my investigation was the Ascorbic Acid concentration in the S. lycopersicum
Variable: which was measured indirectly by the volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution required to turn 25.00𝑐𝑚+ of
the juice extract of the sample blue for 10 seconds.
Measured by:
I used a 50.00𝑐𝑚+ burette to measure the volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution required. I also used a
stop clock to control the rate of addition of the 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution into the 25.00𝑐𝑚+ of
S. lycopersicum and distilled water solution
Unit of Measurement:
I measured volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution required in centimeters cubed (𝑐𝑚+).
Uncertainty:
The uncertainty of the 50.00𝑐𝑚+ burette I used in my investigation was ±0.05𝑐𝑚+.
Table 1.2. The controlled variables of the investigation
Controlled How and why they were controlled
Variables
Volume of 50. 𝟎𝟎𝒄𝒎𝟑 of distilled water
Distilled water I controlled this by using precise equipment to measure the volume of distilled water that would be
used to dilute added. I used a 50. 00𝑐𝑚+ glass measuring cylinder with an uncertainty of ±0.50𝑐𝑚+. The volume of
the S. distilled water was kept the same for each trial as a change in the volume would’ve lead to an incorrect
lycopersicum measurement of the concentration of the S. lycopersicum in the solution therefore, the results gathered
juice will not be valid as the volume of ±0.50𝑐𝑚+would differ per trial and consequentially so, will the
original ascorbic acid content.
Volume of 25. 𝟎𝟎𝒄𝒎𝟑 of S. lycopersicum juice
S. lycopersicum I used a mortar and pestle to juice the already heated up or cooled down S. lycopersicum into a
juice diluted 250.00𝑐𝑚+ glass beaker. I kept the volume controlled through the use of a 50. 00𝑐𝑚+ glass measuring
cylinder with an uncertainty of ±0.50𝑐𝑚+. The volume of S. lycopersicum juice had to remain the same
2
Background Information: S. lycopersicum (tomato) is one of the most important vegetables grown for consumption in
virtually every Nigerian home. Speaking as a Nigerian, it is a common ingredient in many of our traditional meals such as
Jollof rice. This is mainly because scurvy is fairly common and S. lycopersicum has been recognized as a food rich in
ascorbic acid (Vitamin C), so is highly consumed in order to decrease risks of scurvy. Also, S. lycopersicum is one of the
most commonly grown vegetables in Nigeria and is one of the cheapest and most readily available sources of proteins and
vitamins. S. lycopersicum has great nutritional values that include controlling blood sugar through the high chromium
content, helping reduce the risk of heart attacks, strokes and cancer as they contain Vitamin B and potassium and lastly,
helping improve eyesight and strengthening bones through Vitamin A content. However, most Nigerian’s are aware that
there are some disadvantages with consuming too many tomatoes due to its high content in acid and lycopene, for
example, the slowing down of the immune system, acid reflux and Vitamin overdose.
Although S. lycopersicum is a fruit that can be consumed raw, a majority of the time, Nigerian recipes that
involve cooking with S. lycopersicum require boiling at mid to high temperatures for around 20-30 minutes. When
learning how to cook, my mother made sure to inform me that in order to maintain as much minerals and nutrients from
the ingredients, including S. lycopersicum, I would need to ensure proper storage conditions and also try to avoid boiling,
if I couldn’t I should try to minimize the preparation time with as low heat as possible. I always knew that storage
temperature and time as well preparation temperature had an impact on the nutrient content in food products, but it wasn’t
until this course that I learned the scientific reasoning behind the loss of nutrient content. I felt that the knowledge of
deterioration of fresh commodities due to water loss, temperature, ripening and physical damage was fairly common and I
wanted to gain a concrete scientific understanding on what exactly was happening. Therefore, I jumped at the opportunity
to investigate this topic for my biology internal assessment.
However, before carrying out my exploration, I had to decide what nutritional content I would be investigating. I
chose to focus specifically on the ascorbic acid content in the S. lycopersicum. I chose this because after conducting some
research on because it is one of the most popular vitamins known and I already knew a redox titration that would help
calculate the vitamin C content through the IB chemistry course. Prior to beginning my investigation, I found some
information online to give me some background knowledge of Vitamin C. I found that it is considered the only active
isomer of ascorbic acid that needs to be consumed through food and/or other supplements as the body cannot produce it
on its own. Interestingly, I gained new knowledge from my research on vitamin C, as I thought only the basic fruits like
oranges, lemons, etc. contained high vitamin C content but many vegetables like Brussel sprouts and broccoli contain
large amounts of vitamin C as well. The main reason why I chose to investigate this is because of its significant health
benefits in the human body. I learned that, it improves the condition of gums and death, strengthens the blood vessels,
helps heals wounds, regulates redox processes and most importantly, boosts the immune system (Agbemafle, 2815),
which in an environment like West Africa is very beneficial due to the many exposures to diseases such as malaria.
Through unit 1 of the course I was able to learn about
cell membranes and how they are affected by temperature. I
learned that as cellular membranes are composed of many
different proteins, such as integral proteins, that can be
denatured at high temperatures due to a change in the
interaction between certain amino acids that leads to
irreversible changes in the quaternary, tertiary and sometimes
secondary structures of the protein. Then the proteins denature
and lose their form and function. After learning this, I
wondered whether this was the same case with vitamins. In Siane, Fayle ―Redox equilibrium between ascorbic acid
order to find out, I conducted some research. I found that for a and DHA.‖ Food Chemistry, Elsevier, 2000, New York,
majority of vitamins the temperature it is exposed to has a large USA,
https://www.sciencedirect.com/science/article/pii/S03088
impact on the molecule. Specifically, I found that Vitamin C is
14600000777.
an unstable, water-soluble molecule that is vulnerable when
subjected to heat, light and oxygen. At high temperatures, Vitamin C can react and be oxidized and also can leach out, due
to denaturation of the proteins of the cell membrane, into the water and be dissolved. I chose to focus on the oxidation of
Vitamin C into dehydroascorbic acid and the dissolving as the scientific reasoning behind my predictions. Similar to what
happens with proteins, when vitamin C is oxidized it loses its form and function and therefore becomes inactive due to the
addition of oxygen and loss of hydrogen ions (Agbemafle, 2815). All of this intrigued me, as I found irony in the fact that
we try to consume as much vitamin C from S. lycopersicum as possible but end up rendering it useless through the
preparation process and so, I wanted to identify a cause and effect relationship between increasing temperature and
vitamin C content.
1
, There is a very common redox titration that is used to determine the concentration of Vitamin C and it is what I used in
my investigation. Iodine was used as a titrant and starch as an indicator to determine the concentration of vitamin C. I
used Iodine because it can only react with the starch once the ascorbic acid has completely been oxidized and therefore the
number of moles of Iodine used can determine the concentration of ascorbic acid in the sample. I used this method to
determine the effect of temperature on the vitamin C content in S. lycopersicum. I calculated this using the chemistry
titration formula 𝐶1𝑉1 = 𝐶&𝑉& this allows for me to determine the concentration of ascorbic acid (𝐶&) through the
concentration and volume of the Iodine that I used ( 𝐶1𝑉1) and the volume of the sample used (𝑉&).
I did this in order to explore the scientific reasoning behind, what I had been told previously on maintaining
nutrients in food preparation.
Research Question: How does increasing the preparation temperature (00.00℃, 20.00℃, 40.00℃, 60.00℃ and 80.00℃
±0.01℃) of 25.00 ±0.50𝑐𝑚+ Solanum lycopersicum in 100.00𝑐𝑚+ of distilled water, through cooling and boiling affect
its ascorbic acid content; measured indirectly through the volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution (𝑐𝑚+) required to turn
the 25.00𝑐𝑚+ sample blue in a redox titration reaction, using a 50.00𝑐𝑚+ burette (±0.05𝑐𝑚+)?
Variables
Table 1.1. The independent, dependent variables of my investigation
Independent The independent variable of my investigation was the temperature that the 25.00𝑐𝑚+ S. lycopersicum in
variable: 100.00𝑐𝑚+ of distilled water would be prepared in
Measured by:
I used a data harvest temperature probe with the data logger to measure the temperature. I also used an ice
bath and a hot plate to cool down and heat up the 25.00𝑐𝑚+ S. lycopersicum and distilled water sample to the
desired temperatures. The uncertainty of the temperature probe that I used in my investigation was ±0.01°C
Unit of Measurement:
I measured the temperature in degrees Celsius (°C)
Data Range:
00.00°C
20.00°C
40.00°C
60.00°C
80.00°C
Dependent The dependent variable of my investigation was the Ascorbic Acid concentration in the S. lycopersicum
Variable: which was measured indirectly by the volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution required to turn 25.00𝑐𝑚+ of
the juice extract of the sample blue for 10 seconds.
Measured by:
I used a 50.00𝑐𝑚+ burette to measure the volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution required. I also used a
stop clock to control the rate of addition of the 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution into the 25.00𝑐𝑚+ of
S. lycopersicum and distilled water solution
Unit of Measurement:
I measured volume of 0.005𝑚𝑜𝑙 𝐿–1-Iodine solution required in centimeters cubed (𝑐𝑚+).
Uncertainty:
The uncertainty of the 50.00𝑐𝑚+ burette I used in my investigation was ±0.05𝑐𝑚+.
Table 1.2. The controlled variables of the investigation
Controlled How and why they were controlled
Variables
Volume of 50. 𝟎𝟎𝒄𝒎𝟑 of distilled water
Distilled water I controlled this by using precise equipment to measure the volume of distilled water that would be
used to dilute added. I used a 50. 00𝑐𝑚+ glass measuring cylinder with an uncertainty of ±0.50𝑐𝑚+. The volume of
the S. distilled water was kept the same for each trial as a change in the volume would’ve lead to an incorrect
lycopersicum measurement of the concentration of the S. lycopersicum in the solution therefore, the results gathered
juice will not be valid as the volume of ±0.50𝑐𝑚+would differ per trial and consequentially so, will the
original ascorbic acid content.
Volume of 25. 𝟎𝟎𝒄𝒎𝟑 of S. lycopersicum juice
S. lycopersicum I used a mortar and pestle to juice the already heated up or cooled down S. lycopersicum into a
juice diluted 250.00𝑐𝑚+ glass beaker. I kept the volume controlled through the use of a 50. 00𝑐𝑚+ glass measuring
cylinder with an uncertainty of ±0.50𝑐𝑚+. The volume of S. lycopersicum juice had to remain the same
2
