Effect of Time and Heating Temperatures of Water on Vitamin C and Sugar Abundance in Red Delicious Apples

THE INFLUENCE OF DIFFERENT TIME (MIN) AND HEATING TEMPERATUES (°C) OF WATER ON VITAMIN C AND SUGAR ABUNDANCE IN RED DELICIOUS APPLES (100G)

ABSTRACT

Fruits as we all know are crucial to maintaining a healthy body and the most common fruits are apples; as it provides many nutrients and antioxidants. One of the main nutrients that apples contain is Vitamin C. It is one of the most effective antioxidants, which help to grow and repair tissues in all parts of our bodies, for example healing a cut wound. Without enough Vitamin C present in our body, if a cut was present then harmful chemicals and substances within the atmosphere will be able to travel through our bloodstream. Also, there is another important but harmful when overdosed nutrient which is fructose and glucose. As a person who hates crunchy food, and is already overdosing with sugar levels, it led me to the question:

“To what extent does the different temperature of water (50°C, 70°C and 100°C) and time (3min and 6min) that the apple (Red Delicious) is exposed to, affect the Vitamin C (ascorbic acid) and sugar content in Red Delicious, by measuring the concentration of Vitamin C and sugar still remaining in g per 100g of mass?” (e.g. exposing the apple in 50°C for 3 and 6min. Then exposing the apple in 70°C for 3min and 6min etc.)

The 2 independent variables can be measured due to comparing the results of different temperatures at the same time (either 3min or 6min), or different time but same temperature.

For vitamin C content it was done through iodine titration, and for sugar content, the density of the apple sample was compared to the graph of standardized sugar solution (density vs. amount of sugar).

This ultimately lead me to wonder, is there a correlation between Vitamin C and sugar content and how it is affected with an increase in temperature and time; thus, determining just how much sugar is within 1 mg of vitamin C by finding out the ratio, and the findings were phenomenon.

WORD COUNT: 318

CONTENT:

CHAPTER 1

1. INTRODUCTION………………………………………………………………………………………………..
   1.            Research Question…………………………………………………….
   2.            Background Information……………………………………………

CHAPTER 2

2. THE METHODOLOGY
   1.            Preparing the Samples…………………………………………………
   2.            Determining the Vitamin C Content in Red Delicious…….
   3.            Determining the Sugar Content in Red Delicious…………..

CHAPTER 3

3. DATA COLLECTION AND ANALYSIS…………………………………………………………………….
   1.            The Sugar Content……………………………………………………….
   2.            The Vitamin C Content…………………………………………………
   3.            Sugar : Vitamin C ratio…………………………………………………..
   4.            Uncertainties………………………………………………………………….

CHAPTER 4

4. UNCERTAINTIES, CONCLUSION AND EVALUATION…………………………………………….
   1.            Conclusion……………………………………………………………………..
   2.            Evaluation……………………………………………………………………..
   3.            Improvements……………………………………………………………….

BIBLIOGRAPHY……………………………………………………………………………………………………………..

 

 

 

CHAPTER 5

5. APPENDIX………………………………………………………………………………………………………….
   1.            Safety Precautions………………………………………………..
   2.            Proof of Ascorbic Acid Titration…………………………….
   3.            Proof of Iodate and Iodide Reaction………………………
   4.            Measuring the Concentration of Solutions…………….
   5.            Equipment and Apparatus…………………………………….

 

 

 

 

 

CHAPTER 1

1. INTRODUCTION:

My mum always said to me: “An apple a day to keep any physician at bay”. Originating from a typical Asian family, there are only 2 things my parents are overly concerned about: health and education. Although I’ve failed to comply my mums words; as for all my life I’ve despised fruits and vegetables and consumed mostly meat. I’ve neglected all the beneficial nutrients that fruits and vegetables provide for us and only ate what’s more appetising-meat. The only semi-appetising fruit I can handle is apples and through this EE, I’ve finally gotten a chance to investigate just how much nutrients apples really provide for us and whether it’s worthwhile eating.

Apple is usually a round, red, yellow or green edible fruit in a small tree (Malus Sylvestris) of the rose family. An apple contains nearly all the vitamins than humans need for their metabolic processes¹. They are high in fiber- important for digestive health and boron- which promotes bone growth. Also minerals such as calcium, magnesium, sulfur, phosphorus and chlorine are found in all types of apples as well. It is said that one-tenth of our daily potassium needs are contained within one apple which helps to improve our muscle tone. More importantly one of the most known nutrients apple provide is Vitamin C (ascorbic acid) and is one of the most effective antioxidants, which help to grow and repair tissues in all parts of our bodies, for example healing a cut wound. Without enough Vitamin C present in our body, humans are likely to be exposed to more diseases, because harmful bacteria and exposure to harmful chemicals will all travel through our blood into our body while we have a wound open. Thus it is extremely crucial that there is sufficient Vitamin C present to repair the damaged tissues as quickly as possible to avoid unnecessary diseases. It has being discovered that one apple provides roughly 10% of our daily recommended allowance for Vitamin C; an apple weighing 138 grams contains roughly 6.3 milligrams of Vitamin C².

1. https://www.basf.com/fr/fr/we-create-chemistry/creating-chemistry-magazine/food-and-nutrition/the-chemistry-of-apples.html
2. https://www.livestrong.com/article/450127-the-vitamin-c-in-apples/

After discovering the importance of Vitamin C, which every human necessitates. I then questioned the sugar content contained in apples. As we all know sugar is a type of carbohydrate. When carbohydrates are digested and sent into the blood stream they become sugars called glucose. Glucose provides energy when then the cells in our body will absorb. Consuming too much sugar it will cause our body to be resilient to insulin, which is a hormone that allows glucose to enter the cells from the bloodstream and controls the cells to burn glucose instead of fat, thus eating too much sugar will damage this process and will cause many diseases.

This ultimately lead me to think about how to eat an apple. I personally prefer eating soft foods which I can easily sink my teeth into rather than foods that are crunchy and hard. Knowing the fact that heating foods will cause it to become more ripe and soft, and also being the impatient man as I am I also questioned whether the amount of time when heating had an effect on Vitamin C and sugar content in apples. Thus I intend to find out how different heating temperatures of water and time affect the abundance of Vitamin C and sugar levels in apples.

1.1 Research Question

“To what extent does the different temperature of water (50°C, 70°C and 100°C) and time (3min and 6min) that the apple (Red Delicious) is exposed to, affect the Vitamin C (ascorbic acid) and sugar content in Red Delicious, by measuring the concentration of Vitamin C and sugar still remaining in g per 100g of mass?”

(e.g. exposing the apple in 50°C for 3 and 6min. Then exposing the apple in 70°C for 3min and 6min etc.)

1.2 Background Information

Ascorbic Acid

Ascorbic acid (C6H8O6) is a colourless and odourless crystalline substance with a molar mass of 176.12g/mol and is slightly sour in taste. It falls within the class of enolic lactones of glyculosonic acids. The most important member of this class is L-ascorbic acid. (Addy et al, p.200) L-ascorbic acid (C6H8O6) is the trivial name of Vitamin C. The chemical name for ascorbic acid is 2-oxo-L-threo-hexono-1,4- lactone-2,3-enediol (Naidu, 2003).

L-ascorbic acid is a co-factor for hydroxylases and monooxygenase enzymes involved in the synthesis of collagen. Collagen acts like ‘glue’ which helps to hold the cells within our body together resulting in the promotion of skin strength and elasticity, making our skin more durable to cuts.

Humans cannot synthesize ascorbic acid themselves as being a water soluble compound C vitamin is easily absorbed but it is not stored in the body (Naidu, 2003).

The average daily intake level that is sufficient to meet the nutritional requirement of ascorbic acid or recommended dietary allowances (RDA) for adults (>19 yr.) are 90 mg/day for men and 75 mg/day for women (Naidu, 2003).

The stability of ascorbic acid decreases with increase in pH. Therefore high pH substances such as baking soda has a detrimental effect on the destruction of Vitamin C., but is fairly stable in weak acidic solutions. Also ascorbic acid content decreases gradually during storage especially at temperature above 0°C (Oyetade et al, 2012). The average half-life of ascorbic acid is between 16 and 20 days.

Ascorbic acid is reversibly oxidized to dehydroascorbic acid.

Further oxidation of dehydroascorbic acid leads to the irreversible formation of 2,3-diketogulonic acid.

Scheme 3. Oxidation of Dehydroascorbic acid to 2,3-diketogulonic acid

 

 

 

 

 

Fructose and Glucose:

Fructose and glucose are the simplest form of carbohydrates, found in many plants and fruits. They are monomers of sucrose, or are the simple monosaccharides, but when bonded they form the disaccharide of sucrose.

The name mono (one) saccharides (sugar), means that fructose and glucose only contain one sugar group, thus they cannot be broken down any further.

All types of carbohydrates are directly absorbed directly into our blood during digestion and different subtype of carbohydrates has different effects on the body depending on the structure and source (Berg CM, et al). The chemical structure will affect the rate of absorption of the carbohydrate molecules, meanwhile the source of where the carbohydrates came from will determine whether other nutrients are absorbed along with the carbohydrates.

Fructose has a unique texture and a tint of sweetness and has a different rate of digestion compared to glucose; which is the sugar that most of our ingested carbohydrate become when they are absorbed into the bloodstream (Bes-Rastrollo M, et al.). Carbohydrates are an important source of energy for the chemical metabolism in our bodies.

It is extremely controversial where debates of sugar being beneficial or harmful to our body, but in reality, both are correct. When fructose is absorbed through the intestine and enters the liver. In the liver it can then be converted to glucose derivatives and stored as glycogen which is a source of energy for strenuous activities. But too much fructose consumption, will be converted to fat as the liver can only store a limited amount of glycogen, thus are the cause for high-blood pressures and diabetes (Bray GA.)

It is considered that consumption of white sugar should not exceed more than 10% of daily energetic needs. Our body needs daily different carbohydrates, including fibers (Maser et al, 2009).

 

 

 

 

 

 

 

 

 

 

 

CHAPTER 2

 

2.0 THE METHODOLOGY

 

During my background study on this topic, I didn’t find any researchers or sites investigating 2 different independent variables at the same time. There are certain debates that having more than 1 independent variable will falsify the results of dependent variable, as its impossible to tell which independent variable is actually affecting the dependent variable. But I beg to disagree, as if the 2 independent variables are thought out correctly it’s possible to determine the effects of both independent variable.

For my research question with the 2 independent variables being:

• the different temperature of water (50°C, 70°C, 100°C)
• the amount of time (3min and 6min)

By first cooking the apple in 50°C water for 3min and 6min and determining the Vitamin C and sugar content of each apple sample I can use the data found from this to determine whether the amount of time have an effect on the dependent variables. As everything else is kept constant thus eliminating the independent variable of different temperatures.

To determine whether the increase in temperature affect the sugar and Vitamin C content, it can be done by comparing the results found from cooking the apple in 50°C for 3min, 70°C for 3min and 100°C for 3min; where once again eliminating the independent variable of the different time.

There are numerous ways of determining the Vitamin C content, such as through the use of spectrophotometer or redox titration. Due to my lack of knowledge about spectrophotometers I’ve opted redox titration for the determination of Vitamin C (University of Canterbury, n.d.).

As for sugar content, the sugar amount in the investigated apple samples can be evaluated using standardised sugar solutions. By using the sugar solution volume/density ratio standard graph, the mass of sugar in the investigated apple samples can be determined (University of Canterbury, n.d.).

Hypothesis:

If the temperature and time increases when cooking the apple, then the concentration of Vitamin C and sugar content within the apple will decrease, because heat causes the particles to move faster and increases its kinetic energy therefore increases the chances of collisions, thus increasing the intermolecular space between the particles and allowing the Vitamin C and sugar particles to move out of the apple easier.

As the time increases the concentration of Vitamin C and sugar content will also decrease, since the water temperature will be higher than the room temperature, therefore the intermolecular space between the particles will be further apart than an apple under room temperature conditions; thus the longer time it’s in the water the higher chance of Vitamin C and sugar particles to escape through the larger gaps. Also the particles will not possess as much kinetic energy if taken out early, meaning that the particles will be moving less thus having less chance to escape the apple.

 

 

Null hypothesis:

If the temperature and time increases while cooking the apple, the vitamin C content within the apple will not change, due to the fact that the ascorbic acid will be trapped within the outer layers of the apple, as no matter what kinetic energy the particle contains, it will be stopped once it hits an obstacle.

2.1 Preparing the Samples

 

All apparatus, as well as the Red Delicious apples were rinsed with deionised water before conducting the experiment. The apples are then cut into 6 cubes each weighing 100g. Each cube were cut off the same part of the apple, to ensure than the Vitamin C and sugar content are equal, and the volume of the apple were also kept the same so ensure that when cooking it in same amount of water (1dm³) the amount of Vitamin C and sugar particles that escape will be the same due to the same surface area to volume ratio.

Each of the apple pieces were cooking in:

• 50°C water for 3min
• 70°C water for 3min
• 100°C water for 3min

This process was then repeated, but instead of cooking it under 3min it was cooking under 6min instead.

2.2 Determining the Vitamin C Content

 

2.2.1 Equation of Redox reaction between Ascorbic Acid and Iodine:

C₆H₈O₆ (aq) + I₂ (aq) —> 2I^– (aq) + C₆H₆O₆ (aq) +2H⁺ (aq)

for the proof of this equation refer to Appendix (5.2)

 

Instead of just using iodine solution (I₂), the formation of iodine was created using iodate ions and iodide ions, as potassium iodate and potassium iodide ions are more stable, than iodine with the exposure to various of elements in the atmosphere. The potassium ions act as a spectator and does not take place within the reaction.

When iodate ions (IO3-) are added to an acidic solution containing iodide ions (I^–), an oxidation-reduction reaction occurs:

IO₃^– (aq) + 5I^– (aq) +6H⁺ (aq)  3I₂ (aq) +3H₂O (l)

For proof of equation refer to Appendix (5.3)

 

 

 

It is the iodine formed by this reaction then oxidises the ascorbic acid to dehydroascorbic acid as the iodine is reduced to iodide ions:

C₆H₈O₆ (aq) + I₂ (aq) —> 2I^– (aq) + C₆H₆O₆ (aq) +2H⁺ (aq)

Iodine will continue to be reduced since ascorbic acid acts as a reducing agent, where when ascorbic acid is present, iodine will continue to be reduced to I-, due to the fact that ascorbic acid will continue to give up its electrons and push it towards iodine atoms. Until the moment when ascorbic acid’s electrons are all used up, that’s when the excess iodine is free to react with the indicator (starch in this case), forming the blue-black starch-iodine complex – indicating the end point of the titration.

2.2.2 Creating the Required Solutions (refer to Appendix5.4):

0.5% starch

Potassium iodate solution (0.002 MOL)

Potassium iodide solution (0.6 MOL)

Hydrochloric acid (1 MOL)

20 cm³ Ascorbic acid

The amount and concentration of each of these solutions were kept constant to ensure the same mols of each solution was reacted, which is important as the amount of Vitamin C content will be determined with mol ratios between potassium iodate and ascorbic acid. Also, for a reaction to occur the KIO₃ particles need to collide with KI, ascorbic acid and also starch; thus too much or too little of any solution (excluding KIO₃)will hinder KIO₃ particle’s chance to collide and react with the required solutions, thus will falsify the results of the titres due to the fact that the results will also be affect by the concentration and amount of solutions used.

2.2.3 Vitamin C extraction:

The 6 pieces of apple after cooking them, were then taken out and was grinded using a pestle and mortar. After no more juice can be extracted out the apple piece was taken out and the juice was mixed with 30cm³ of distilled water. The solution was then poured into a volumetric flask and distilled water was added until the total volume hit 100 cm³.

2.2.4 Titration:

20ml of ascorbic acid was transferred into a conical flask, with the addition of 5cm³ HCl, potassium iodide (KI) and 1 cm³ starch indicator. The conical flask was then placed under the burette which was filled with 50cm³ of KIO₃ (potassium iodate). The end point was the titration was at the point where a blue-black colour change occurred, and the amount of KIO₃ was recorded when this colour change occurred. This experiment was repeated 3 times, to ensure the average titre of KIO₃ were within (0.1 cm³).

2.3 Determining the Sugar Content

2.3.1 Creating standard sugar solution volume/density ratio graph

By first determining that sugar solution(fructose/glucose) is in aqueous state and sugar under room temperature it’s solid state, the conversion of 1cm³ of sugar volume is equal to 0.85g of sugar mass. Also considering that 1cm³ of distilled water is equivalent to 1g.

Each of the 5cm³, 10cm³, 15cm³ (4.25g, 8.5g and 12.75g) of sugar is poured into a 100cm³ beaker, which was then filled with distilled water until the final volume hit 50cm³ (e.g. for 5cm³ sugar, 45cm³ of distilled water is added). The beaker was weighed before the solution was poured, so the mass of the solution can be determined. As the mass of beaker was subtracted from the total mass (solution + beaker). The density was then determined using the formula

=mv

(density equals mass divided by volume). After determining the density of each sugar concentration, the results were graphed with the independent variable (x-axis) being the amount of sugar (cm³) and the dependent variable (y-axis) being the density.

2.3.2 Calculating Sugar content in Apple Sample:

After no more juice can be extracted out the 100g apple piece was taken out and the juice was mixed with 30cm³ of distilled water. The solution was poured into a 100cm³ beaker and distilled water was added until the final solution hit 50cm³. Similarly, density can then be found (refer to 2.3.1) thus using the graph from 3.1.1(refer to graph 1 under results section) and comparing the density of the apple sample to the graph of standardized sugar solution (density vs amount of sugar), the sugar content can then be determined for the apple samples.

CHAPTER 3

 

3.1 Calculating Sugar Content:

Formulas to consider:

=mv

3.1.1 Creating standardized sugar solution graph:

5cm³ fructose (1cm³ sugar is equal to 0.85g)

5 x 0.85 = 4.25g

45cm³ distilled water (1cm³ water is equal to 1g)

45 x 1 = 45g

Total volume = 5 + 45 = 50cm³

Total mass = 4.25 + 45 = 49.25g

=49.2550

=

0.985 g/cm³

10cm³ fructose

10 x 0.85 = 8.5g

40cm³ distilled water

40 x 1 = 40g

Total volume = 10 + 40 = 50cm³

Total mass = 8.5 + 40 = 48.50g

=48.550

=

0.970 g/cm³

 

 

 

 

 

 

 

 

15cm³ fructose

15 x 0.85 = 12.75g

35cm³ distilled water

35 x 1 = 35g

Total volume = 15 + 35 = 50cm³

Total mass = 12.75 + 35 = 47.75g

=47.7550

=

0.955 g/cm³

Table 1. The density of different fructose solution (5,10,15cm³) and the mass of sugar.

Amount of sugar (cm3) 0.05cm3	Mass of solution -sugar + water    (g) 0.01g	Density of solution (g/cm3)	Mass of Sugar (g) 0.01g
5	49.25	0.985	4.25
10	48.50	0.970	8.5
15	47.75	0.955	12.75

Graph 1: Sugar solution volume : density ratio standard graph

3.1.2 Calculating the Density of Sugar Solution Within Each Apple Samples (100g) at Different Temperature and Time:

Using the same density formula:

=mv

Table 2: Density of different sugar content within the 100g apple samples under different temperature and time.

Temperature (oC)	Time (min)	Volume (cm3)	Mass (g)	Density (g/cm3)
50	3	50	48.21	0.964
50	6	50	48.50	0.970
70	3	50	48.82	0.976
70	6	50	49.01	0.980
100	3	50	49.20	0.984
100	6	50	49.60	0.992

By comparing the density of the apple sample to the graph of standardized sugar solution (graph 1), the sugar content can then be determined for the apple samples.

 

This illustrates that at 0.964 g/cm³ density the sugar volume is 11.8cm³, for the apple sample that was cooked in 50^oC water for 3min. This process was repeated for all the other conditions and the results are tabulated.

Table 3: Comparing the density to graph 1 to determine the sugar mass (g) still containing within 100g of apple sample under each condition.

Temperature (oC)	Time (min)	Density (g/cm3)	Sugar Volume (cm3)	Sugar Mass (g)
50	3	0.964	11.80	10.03
50	6	0.970	9.64	8.19
70	3	0.976	7.49	6.37
70	6	0.980	6.32	5.37
100	3	0.984	5.12	4.35
100	6	0.992	2.86	2.4

Remembering that 1cm³ fructose is equivalent to 0.85g in mass.

e.g. 11.8 x 0.85 = 10.03g of sugar

Graph 2: Comparison of Sugar Amount in 100g Apple Sample

The results on this graph illustrates that as temperature increases when time is kept constant, the amount of sugar in the sample decreases. At each of the same temperature but different time, the apple that’s cooked for longer had less sugar content. Also, as time increases, the black line transitions down from the y axis, illustrating that if the apples were cooked longer, the amount of sugar content will decrease. The 2 lines are parallel having the same gradient, meaning that the sugar content with increasing time will always have less content under the same temperature, as the 2 times will never intersect with the same gradient, therefore the orange line will always be below the black line. It can also be safe to say that for temperature <50^oC the sugar content will be greater than the sugar content at 50^oC and for temperature >100^oC the sugar content will be less than the sugar content at 100^oC. This result also illustrates, from ascending order of sugar content still remaining in 100g of apple:

100^oC (6min) < 100^oC (3min) < 70^oC (6min) < 70^oC (3min) < 50^oC (6min) < 50^oC (6min). This also shows, from the graph that temperature affects the sugar content more than time, because 100^oC (3min) had less sugar content than 70^oC (6min); and 70^oC (3min) < 50^oC (6min). Since from the result it’s safe to say that the increase in time and temperature will result in a decrease in sugar content, therefore comparing the higher temperature with less time and lower temperature with more time showed that higher temperature caused the sugar content to decrease more. But this finding cannot generalise that the increase in temperature will affect sugar content more than time, as the values of time and temperature was chosen randomly and may not have a direct correlation (e.g. if it was 3min and 8min, and the temperatures were still the same, then the results will be different).

3.2 Calculating Vitamin C Content:

 

Table 4: average titre (cm³) of KIO₃ (0.002MOL) used for each apple sample under these conditions.

Temperature (oC)	Time (min)	Titre 1 (cm3)	Titre 2 (cm3)	Titre 3 (cm3)	Average Titre (cm3)
50	3	1.34	1.33	1.34	1.34
50	6	1.12	1.10	1.13	1.12
70	3	1.05	1.03	1.03	1.04
70	6	1.01	0.99	0.98	0.99
100	3	0.92	0.93	0.92	0.92
100	6	0.81	0.80	0.80	0.80

Reactions to Consider:

1. IO₃^– (aq) + 5I^– (aq)  3I₂ (aq) +3H₂O (l)
2. C₆H₈O₆ (aq) + I₂ (aq) —> 2I^– (aq) + C₆H₆O₆ (aq) +2H⁺ (aq)

For the apple sample undergoing 50^oC of water for 3min:

Concentration of KIO₃ (0.002mol per 1dm³), and knowing that:

1 dm³ = 1000 cm³

0.0021000

= 0.000002 MOL (per 1 cm³)

Average titre of KIO₃ : 1.34 cm³

n

=CV

(mols = concentration x volume)

1.34 x 0.000002 = 0.00000268 mol of KIO₃

Referring to reaction 1.

1 IO₃^– : 3 I₂

1 mol of IO₃^– is equivalent to 3 mol of I₂

0.00000268 x 3 = 0.00000804 mol of I₂

Referring to reaction 2.

1 I₂ : 1 C₆H₈O₆

Mol ratio is 1:1

0.00000804 x 1 = 0.00000804 mol of C₆H₈O₆

M (C₆H₈O₆) = 176g

Mass = molar mass x mol

0.00000804 x 176 = 0.001415g (1.415 mg) of ascorbic acid in 20 cm³ of ascorbic solution.

The total ascorbic acid of 100g apple sample was within 100cm³ of ascorbic solution, and the calculation was only for 20cm³.

20 : 100 = 1 : 5 ratio

1.415 x 5 = 7.075mg per 100g of apple

Repeating the process for each condition:

Table 5: amount of Vitamin C (mg per 100g) of apple in each condition

Temperature (oC)	Time (min)	Amount of Vitamin C (mg per 100g)
50	3	7.075
50	6	5.966
70	3	5.438
70	6	5.174
100	3	4.858
100	6	4.224

Graph 3: The Vitamin C content (mg) of 100g apple sample under different conditions.

This graph illustrates that the increase in temperature will reduce the amount of Vitamin C content in apples as shown either through the blue line or the orange line. Similarly, as time increases the Vitamin C content will also decrease, through comparing the results found with same temperature but different times. Following the trend, it can be safe to say that for temperature <50^oC the apples will contain more vitamin C, and for temperature >100^oC the apples will contain minimal vitamin C content. Also, as time increases the black line transitions down from the y axis, illustrating that if the apples were cooked longer the amount of vitamin C content will again, decrease. The black and orange lines are parallel, meaning that the black line will never intersect with the orange line as they have the same gradient, which is safe to assume that an increase in time will always result in less vitamin C content under the same temperature.

3.3 Calculating the vitamin C to Sugar content ratio

The calculations from 3.1 and 3.2 helped me to determine the amount of sugar and vitamin C content left, but I wanted to investigate the correlation between Vitamin C and sugar content and how it is affected with an increase in temperature and time; thus determining just how much sugar is within 1 mg of vitamin C, thus finding out the ratio:

 

Table 6: The Sugar : Vitamin C ratio in 100g apple sample under each conditions.

Temperature (oC)	Time (min)	Sugar Mass (mg)	Vitamin C content (mg)	Sugar : Vitamin C ratio (mg : mg)
50	3	10030	7.075	10030 : 7.075 Simplified to: 1417.67 : 1
50	6	8190	5.966	1372.78 : 1
70	3	6370	5.438	1171.39 : 1
70	6	5370	5.174	1037.88 : 1
100	3	4350	4.858	895.43 : 1
100	6	2400	4.224	568.18 : 1

Graph 4: The sugar content per 1mg of Vitamin C under different conditions.

By comparing the results of different temperatures at the same time, the ratio of sugar to vitamin C content showed that an increase in temperature will cause the ratio to decrease meaning that there is less sugar content per 1 mg of vitamin C; similar to an increase in time at the same temperature. From this graph it can be said that an increase in temperature will affect the ratio more than an increase in time because, the sugar content per 1mg of vitamin C in 70^oC (3min) is lower than 50^oC in 6min and 100^oC (3min) < 70^oC (6min). This can be safe to say that if the temperature is increased by 25^oC~ (average of

70-50+(100-70)2

) and time increased by 3min, the temperature will reduce the sugar content more per 1mg of vitamin C. This result can’t be generalised because if the time was 10min rather than 6min, and following the trend that an increase in time will result in less sugar content per 1mg of vitamin C, the results e.g. 50^oC (10min) compared to 70^oC (3min) will be different, because 50^oC (10min) will have a lower sugar to vitamin C ratio than the previous 50^oC (6min), thus the results of sugar : vitamin C ratio might be equal or less than 70^oC (3min). Also, if there are 10mg vitamin C present then 100^oC (6min) will have the least sugar content (568.18 x 10 = 5682mg) and 50^oC (3min) will have the most sugar content (1417.67 x 10 = 14177mg).

3.4 Calculating Uncertainty:

 

Percentage error =

uncertaintyAmount measured

x 100

3.4.1 %error in determining sugar content:

Instrument	Uncertainty	Percentage Error
Electronic Balance   (weight of 50cm3 apple juice)	0.01g	%Error=0.0148.21 x 100= 0.021% %Error=0.0148.50 x 100= 0.021% %Error=0.0148.82 x 100= 0.020% %Error=0.0149.01 x 100= 0.020% %Error=0.0149.2 x 100= 0.020% %Error=0.0149.6 x 100= 0.020% Total % error: 0.102%
Measuring cylinder   (volume of apple juice – 50cm3 )	0.01cm3	%Error=0.0150 x 100= 0.020% Total % error: %Error=0.0150 x 100= 0.020% x 6 = 0.02 x 6 = 0.120%

Total % error in determining sugar content:

0.120% + 0.102% = 0.222%

e.g.

=48.2150

= 0.964 (g/cm³)

the total % error of the mass + volume is: 0.021% + 0.020% = 0.041%

0.964 x 0.041% = 0.000395 g/cm³

0.964 – 0.000395 = 0.9636 g/cm³

0.964 + 0.000395 = 0.9644 g/cm³

This illustrates that the density can range from 0.9636 to 0.0644, which are very minimal errors.

3.4.2 %error in determining Vitamin C:

Instrument	Uncertainty	Percentage Error
Electronic Balance   Mass of Apples (100g)	0.01g	%Error=0.01100 x 100= 0.01% Total % error (6 x 100g apple samples) 0.01% x 6 = 0.06%
Measuring Cylinder   Volume of Ascorbic Acid(20cm3)	0.01cm3	%Error=0.0120 x 100= 0.05% Total % error (6 x 20cm3 ascorbic acid) 0.05% x 6 = 0.3%
Burette   Amount of KIO3	0.02cm3	%Error=0.021.34 x 100= 1.493% %Error=0.021.12 x 100= 1.786% %Error=0.021.04 x 100=1.923% %Error=0.020.99 x 100= 2.020% %Error=0.020.92 x 100= 2.174% %Error=0.020.8 x 100= 2.500% Total % error: 1.493+1.786+1.923+2.02+2.174+2.5 = 11.896%
Plastic Pipette (3cm3)   Volume of HCl (5cm3)   Volume of KI (5cm3)   Volume of starch (1cm3)	0.05cm3	FOR HCl %Error=0.055x 100= 1% Total % error (6 titrations) 1 x 6 = 6% FOR KI %Error=0.055 x 100=1 % Total % error (6 titrations) 1 x 6 = 6% FOR STARCH %Error=0.021 x 100= 2% Total % error (6 titrations) 2 x 6 = 12% TOTAL % ERROR (HCl, KI, Starch) 12 + 6 + 6 = 24%

Total error in determining Vitamin C:

0.06% + 0.3% + 11.896% + 24% = 36.256%

Total error in 1 titration of 50^oC (3min) apple sample:

0.01% + 0.05% + 1.493% + 1% + 1% + 2% = 5.553% total error

If the vitamin C (refer to results) was found to be 7.075mg per 100g, this result has a 5.553% error:

7.075 x 5.553% =  0.393 mg difference from the actual results

7.075 – 0.393 = 6.682 mg per 100g of apple

7.075 + 0.393 = 7.468 mg per 100g of apple

This shows that the Vitamin C content remaining of the 100g apple cooked in 50^oC for 3min, can vary between 6.682mg to 7.468mg.                                    RESULTS TOTAL WORD: 2187

CHAPTER 4:

 

 

4.1 CONCLUSION:

From these experimental results, it supported the hypothesis, where the increase in both temperature and time will decrease both sugar and vitamin C content in 100g of apple sample, because heat will cause the intermolecular space between the particles to expand, thus allowing the nutrients to escape more easily while possessing a greater kinetic energy. Though testing whether time and temperature affected the vitamin C and sugar content was only a part of the whole experiment; the other was to determine what is the best condition to eat an apple? 50^oC heating is the minimum temperature for the apple to become ripe and soft. The results showed that for apples that was cooked in 50^oC (3min), it contained the most vitamin C and sugar content, with 7.075mg and 10.03g respectively. Also, when the apples were cooked in 100^oC(6min) it contained the least amount of vitamin C and sugar content, with 4.224mg and 2.4g respectively. Therefore, eating the apples when cooked in 50^oC for 3min is the best choice, since it contains the most amount of vitamin C, but the sugar levels are relatively high. The results from sugar to vitamin C ratios showed that per 1mg of vitamin C there are 1417mg (1.417g) of sugar, which is the highest amount. The least was 568mg (0.568g) of sugar per 1mg of vitamin C which was the apples that was cooked under 100^oC for 6min. Therefore, for a person who is suffering illnesses such as diabetes its best for them to eat the apples cooked in 100^oC, as it contains the least amount of sugar per 1mg of vitamin C. If they were to consume 10mg of vitamin C then the amount of sugar will be 5.68g (10 x 0.568); whereas if the apples were in 50^oC (3min) the amount of sugar in 10mg of vitamin C will be 14.17g, which is 8.48g of sugar more than the apples cooked in 100^oC.

4.2 EVALUATION:

During the experiment there are always unavoidable inaccuracies, thus resulting in some of the discrepancies in the true values of ascorbic acid and sugar content.

Firstly, not all the apple samples will be cut to exactly the same mass, although in methodology, it intended that. An increase in mass will resulted more vitamin C content after titration, because more mols of Iodine will be needed to react with the extra ascorbic acid as the more the mass is the more ascorbic acid it’ll contain. This is a redox reaction where the iodine will continue to be reduced to I^–, while C₆H₈O₆ will lose its electrons (oxidised). If there is C₆H₈O₆ available, then the iodine will continue to react with it, until there is none left thus reacting with the starch indicator within the solution. Also, the mass of the apples will still be containing some water due to the rinsing of the samples thus adding weight while measuring the 100g sample.

Also, part of the apple where the 100g sample was cut from can also cause an inaccuracy in the results, as some part of the apples might be vitamin C / sugar rich or deficient. Though 100g sample was fundamentally ¾ of the apple, the vitamin C and sugar content will not be affected greatly as shown from the consistent results above.

The volume of the apple samples was fairly close, but small differences still exist thus will have slightly different surface area to volume ratio. The more surface area to volume, the more vitamin C and sugar it’ll lose, because the particles will have less distance to travel out of the apple and into the water.

While extracting the vitamin C and sugar, it was grinded using mortar and pestle, thus the content extracted out might be inconsistent. To minimize this error, a marker was made in the mortar and once the juice reached that level. The extraction was stopped to ensure that the amount of ascorbic acid and sugar extracted was kept constant, as stated above too less or too much ascorbic acid will affect the amount of KIO₃ needed.

Furthermore, because of the solubility of vitamin C, it might have resulted in leeching while placed in water. This error cannot be controlled as the whole purpose of this experiment was to cook the apples in water.

Although the uncertainties were extremely low; that is only if the readings of the volume were accurate. The volumes were assumed to be similar to what methodology stated, but some human errors cannot be avoided such as readings of volume at eye level. Some systematic errors may also occur as the equipment were really old and some substances may have stuck onto it, thus creating an inaccurate reading of volume as those substances will contribute to the total volume.

The temperature of water bath was not constantly heated and was placed under room temperature which had a lower temperature than the water bath, therefore overtime the temperature will decrease as heat will be transferred to the surrounding. The water bath with the highest temperature will lose the most heat, due to the greater heat content discrepancies compared to the room temperature, thus the rate of heat loss will be greater.

For determining sugar content, 1 major flaw was the fact that when extracting it the solution did not only contain fructose and glucose, but also other substances and each substance might have a different mass, which will result in an inaccurate reading of mass for 50cm³ of solution.

4.3 IMPROVEMENTS:

Several improvements can be made for the experiment, starting with slightly altering the research question to avoid the apples being exposed in water, as the solubility of vitamin C will result in leeching.

Due to my lack of knowledge with some of the technical equipment such as spectrophotometre I’ve opted for redox titration for determining the vitamin C content and this method consists of many errors as shown in table 3.4.2 where the total % error of using a burette and pipette is 35.896%. Also, through titration the particles of iodine need to collide with the ascorbic acid, then with starch, and the collision is dependent of chance, therefore may cause an inaccuracy in the results. So, for future reference, I’ll learn some advanced technologies to eliminate those % errors when done by titration.

The temperature of water baths can easily be kept constant next time, by boiling the water using flame and using a thermometer to measure each of the conditions, thus determining the intensity of flame in order to keep those temperatures constant.

Due to the outlier results from graph, a line of regression (line of best fit) was drawn to eliminate those outlier results, thus getting a more accurate reading for the Vitamin C and sugar content under those conditions.

Overall the experiment was successful, as the results were consistent, and trends were able to be properly identified, which ultimately supported the hypothesis.

BIBLIOGRAPHY:

1. Oyetade et al, 0.9-10.2012, Stability Studies on Ascorbic Acid (Vitamin C) From Different Sources, IOSR Journal of Applied Chemistry (IOSR-JAC) ISSN: 2278-5736, Volume 2, Issue 4, PP 20-24

2. A national resource for computational science education, (n.d.), Determining the Amount of Sugar in Soft Drinks, Available: http://www.shodor.org/ssep/lessons/soda/sugar.html [21 Apr 2018]

3. University of Canterbury, (n.d.), Determination of Vitamin C Concentration by Titration, Available: http://www.chemteach.ac.nz/investigations/documents/vitaminc_iodate.pdf [21 Apr 2018]

4. United States Department of Agriculture, Agricultural Research Service, (n.d.), National Nutrient Database for Standard Reference, Available: http://ndb.nal.usda.gov/ndb/foods/show/8395 [22 Apr 2018]

5. Naidu K Akhilender, 2003, Vitamin C in human health and disease is still a mystery? An overview, Nutrition Journal 2:7

6. Fyhle et al, 2013, Organic Chemistry 11th Edition, John Wiley & Sons, Inc.

7. Grzegorz Bartosz, 2014, Food Oxidants and Antioxidants, Chemical, Biological and Functional properties, Taylor & Francis Group, LLC

 

 

 

 

 

CHAPTER 5

5.0 APPENDIX

 

5.1 Safety precautions:

Chemical	Hazard	Precautions
HCl	corrosive	Handle with care. Rinse thoroughly with water if skin is in contact
Iodine solution (created through KIO3 and KI)	Corrosive and carcinogenic	Handle with care Rinse thoroughly with water if skin is in contact
Boiling Water	Skin burn	Handle with care Wash skin with cold water if skin is in contact

5.2 proof of redox reaction between ascorbic acid and iodine

C₆H₈O₆ (aq) + I₂ (aq) —> 2I^– (aq) + C₆H₆O₆ (aq) +2H⁺ (aq)

Oxidation state:

C₆H₈O₆, carbon atom has an oxidation state of +

23

I_2, has an oxidation state of 0

2I^–, has an oxidation state of -1

C₆H₆O₆, carbon atom has an oxidation state of +1

Reduction (gain of electrons)

I₂  I^–

After balancing equation

I₂  2I^–

After balancing the charges (half equation)

2I₂ + 2e^–  2I^–

Oxidation (loss of electrons)

C₆H₈O₆  C₆H₆O₆

After balancing the equation:

C₆H₈O₆  C₆H₆O₆ + 2H⁺

After balancing the charges (half equation)

C₆H₈O₆  C₆H₆O₆ + 2H⁺ + 2e^–

Overall equation:

Reactants of oxidation + reduction  products of oxidation + reduction

2I₂ + 2e^–  2I^– + C₆H₈O₆  2I^– + C₆H₆O₆ + 2H⁺ + 2e^–

Gaining 2e^– ions (Right hand side of equation) and losing 2e^– (LHS) means that the electrons are all used up:

C₆H₈O₆ (aq) + I₂ (aq) —> 2I^– (aq) + C₆H₆O₆ (aq) +2H⁺ (aq)

5.3 Proof of redox reaction between iodate and iodide

IO₃^– (aq) + 5I^– (aq) + 6H⁺ (aq)  3I₂ (aq) +3H₂O (l)

Oxidation State:

IO₃^–, iodine atom has an oxidation state of +5

I^–, iodine atom has an oxidation state of -1

I₂, iodine atom has an oxidation state of 0

Reduction (gain of electrons)

IO₃^–  I₂

After balancing the iodine atoms

IO₃^– 

12

I₂

After balancing the O atoms (adding H₂O)

IO₃^– 

12

I₂ + 3H₂O

After balancing the H atoms (adding H⁺)

IO₃^– + 6H⁺ 

12

I₂ + 3H₂O

After balancing the charges (half equation)

IO₃^– + 6H⁺ + 5e^– 

12

I₂ + 3H₂O

Oxidation (loss of electrons)

I^–  I₂

After balancing the equation:

I^– 

12

I₂

After balancing the charges

I^– 

12

I₂ + e^–

Need to balance e^– ions for the 2 half equations:

(I^– 

12

I₂ + e^–) x 5

5I^–  2

12

I₂ + 5e^–

Overall equation:

Reactants of oxidation + reduction  products of oxidation + reduction

IO₃^– + 5I^– +6H⁺ + 5e^–  3I₂ + 3H₂O + 5e^–

Cancelling the 5e^– on both side, as they are used up during the reaction:

IO₃^– + 5I^– +6H⁺ + 5e^–  3I₂ + 3H₂O + 5e^–

5.4 Creating the Required Solutions for Vitamin C Titration:

 

0.5% starch indicator solution

• Starch is solid under room temperature
• Knowing 1cm³ of distilled water is 1g
• 0.5% means there is 0.5% starch within a given volume

% by mass =

mass of starch (g)total mass (g) (water+starch)

x 100

0.5% =

0.5100

x 100

0.5g of starch and 99.5 cm³ of water.

Or

0.05g of starch and 9.95 cm³ of water.

 

Potassium iodate solution (0.002 MOL)

• Solid in room temperature
• Knowing the molar mass is 214.001g/mol

 

For 1 mol per dm³, 214.001g KIO₃ is needed

For 0.002 mol per dm³:

0.002 x 214.001 = 0.428g of KIO₃ is needed for 1dm³ of total volume

1cm³ of water = 1g

Thus 0.428g of KIO₃ and 999.572cm³ distilled water is needed

Or

0.0428g of KIO₃ and 99.9572cm³ distilled water is needed

 

 

 

Potassium iodide solution (0.6 MOL)

• Solid in room temperature
• Knowing the molar mass is 166.0028g/mol

 

For 1 mol per dm³, 166.0028g KI is needed

For 0.6 mol per dm³:

0.6 x 166.0028 = 99.602g of KI is needed for 1dm³ of total volume

1cm³ of water = 1g

Thus 99.602g of KI and 900.398cm³ distilled water is needed

Or

9.9602g of KI and 90.0398cm³ distilled water is needed

 

Hydrochloric acid (1 MOL)

• Liquid in room temperature

Equations to Consider:

Mols = C x V (mols equal to concentration x volume)

Therefore:

C₁V₁ = C₂V₂

The original sample of HCl had a concentration of 5mol per 1dm³ and I wanted to make 0.05dm³ of 1mol per dm³ HCl.

5 x V₁ = 0.05 x 1

5V₁ = 0.05

V₁ =

0.055

V₁ = 0.01 dm³ (10cm³) of 5MOL HCl needed

In order to get to 50cm³ total volume, 40cm³ of distilled water is added.

5.5 Equipment and Apparatus:

• A weighing scale

  ±0.01g

• 1x 50cm³ burette
• 1x Clamp and stand
• 1x pestle
• 1x mortar
• 1x kettle
• 1x sharp knife
• 1x cutting board
• 1x burette funnel
• 4x 25 cm³ pipette
• 1x 100 cm³ measuring cylinder
• 6x 250 cm³ conical flask
• 6x 250 cm³ beaker
• 3x spatula
• 4x plastic plate
• 1x thermometer
• Apples (Red Delicious)
• 300 cm³ potassium iodate solution (0.002 MOL)
• 30 cm³ potassium iodide solution (0.6MOL)
• 6 cm³ starch indicator solution (0.5%)
• 30 cm³ Hydrochloric acid (1MOL)
• 1 dm³ distilled water
• 30 cm³ sugar