LABORATORY REPORT 3

SBF 3013 BIOCHEMISTRY

LABORATORY 3

TITLE: Carbohydrate (Project)

Name	Matric number
Sharifah Awanis bt Syed Mohd Aswad	D20141067053
Maureen Santih ak Ambang	D20141067070
Heidi Amelda ak Lagat	D20141067086

LECTURER: ASSOCIATE PROFESSOR ROSMILAH BINTI MISNAN

INSTRUCTOR: NUR ATIEKAH BINTI AZAHARI

Laboratory 3 Carbohydrate (Project)

Title: Measuring Vitamin C using starch – iodine test

Introduction:

Vitamin C, also known as L-ascorbic acid and also is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. One way to determine the amount of vitamin C in food is to use a redox titration. The redox reaction is better than an acid-base titration since there are additional acids in a juice, but few of them interfere with the oxidation of ascorbic acid by iodine.

We will measure the amount of vitamin C in many different types of foods. The chemical reaction we will use to measure the amount of vitamin C uses one of its functions in the body. Vitamin C involves in our cells oxidation-reduction reactions. Vitamin C can react with iodine. Therefore we will measure the amount of vitamin C by adding iodine to our food extracts until the vitamin C can bind no more iodine. Iodine in excess of the vitamin C will react with a starch solution you will add to the extract to produce a bluish-black colour. The addition of a chemical to measure another chemical is called a titration.

Materials:

1. Vitamin C standard (0.2 mg/ml)

2. Food sources of vitamin C: for example juices, extraction of plants, flowers, fruits, grains, and vegetables, vitamin C tablet or cooked/treated food sample (boiled/refrigerated/grilled)

3. Starch solution (1%): Mix 1 g starch in 100 ml boiling H2O. Boil for one minute while stirring. Stir until completely dissolved (this solution will be cloudy).

4. Iodine solution: Mix 0.6 g potassium iodide in 500 ml H2O. Mix 0.6 g iodine in 50 ml of ethyl alcohol. These two iodine solutions should be mixed well before combining. Combine the two iodine solutions and add an additional 450 ml of H2O.

5. Hydrochloric Acid (HCl) 1 M, (5 ml)

6. Blender

7. Filter/ cheesecloth

Procedures:

The apparatus are set up as shown.

1.      Preparing the vitamin extracts

                                i.            Food material is chopped into small pieces and placed into blender.

                              ii.            100 ml of distilled water is added into the blender.

                            iii.            The material is blended thoroughly ground using the highest speed.

                            iv.            The ground extract is strained.

                              v.            30 ml of the strained extract is measured into a 250 ml Erlenmeyer flask or beaker.

2.      Measuring vitamin C in the standard and food sample.

                                i.            30 ml of vitamin C standard is placed in a 250 ml of flask or beaker.

                              ii.            2 drops of the 0.1 M HCl are added to the flask.

                            iii.            5 ml of the starch solution is added into the flask.

                            iv.            A burette is filled with the iodine solution.

                              v.            The initial volume reading is recorded.

                            vi.            In 1 ml incremenents of iodine solution to the flask while swirling the flask.

                          vii.            Iodine is added until the solution stays blue-black for 15 seconds.

                        viii.            The volume reading on the burette is recorded.

                            ix.            Step i to viii are repeated to measure the vitamin C in the food sample.

                              x.            The amount of vitamin C in the food sample is calculated using the formula :

 

3.      Comparing cooked food and raw food’s vitamin C:

                                i.            Food is prepared by our own creativity. For example, we can boil or steam or place in a freezer. We also can prepare the food by different exposing time to heat etc.

                              ii.            Food material is chopped into small pieces and placed into blender.

                            iii.            Data is obtained using the same method in previous method.

                            iv.            The volume reading on the burette is recorded.

                              v.            The relative amounts of ascorbic acid present in the samples we are testing are compared.

                            vi.            The results are compared with those other members of the class. What do the results show?

2. Application: Magic Writing

Materials:

Beaker

Iodine

Lemon/Lime juice

Notebook paper

Cup

Art brush

Procedure:

Step A : iodine solution

1.      100 ml of water are poured into 500 ml – beaker.

2.      10 ml of iodine are added to the water and stirred.

Step B :

1.      A section from the notebook paper is cut.

2.      The paper must fit inside a 500 ml beaker.

Step C: Vitamin C solution

1.      The juice of the lemon/lime is squeeze into another beaker.

Step D:

1.      The art brush ia dipped into the lemon/lime juice.

2.      A message is written on the piece of paper.

3.      The juice is allowed to dry on the paper.

4.      The paper is submerged in the iodine solution in the bowl.

Result:

Measuring Vitamin C using starch – iodine test (Project)

Samples	Volume of iodine measured (ml)	Amount of vitamin C in sample (mg/ml)
Vitamin C Standard	15.5 & 14.7 (15.5 + 14.7)/2 = 15.1	0.2 mg/ml
Ice cream soda	0.4	(0.2 mg/ml /15.1 ml) x 0.4 ml = 5.30 x 〖10〗^(-3)  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =(50/100) x 30                              =15 g  In 15 g ice cream soda = 5.30 x mg/ml In 100 g orange = (5.30 x 〖10〗^(-3) /15) x 100             = 0.353 mg/ml vitamin C
Orange (untreated)	16.5	(0.2 mg/ml /15.1 ml) x 16.5 ml = 0.219  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.219 mg/ml In 100 g orange = (0.219/15) x 100                      = 1.46 mg/ml vitamin C
Orange (treated)	15.2	(0.2 mg/ml /15.1 ml) x 15.2 ml = 0.201  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.201 mg/ml In 100 g orange = (0.201/15) x 100                      = 1.34 mg/ml vitamin C
Chrysanthemum (untreated)	12.5	(0.2 mg/ml /15.1 ml) x 12.5 ml = 0.166  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.166 mg/ml In 100 g orange = (0.166/15) x 100                      = 1.11 mg/ml vitamin C
Chrysanthemum (treated)	32.5	(0.2 mg/ml /15.1 ml) x 32.5 ml = 0.430  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.430 mg/ml In 100 g orange = (0.430/15) x 100                      = 2.87 mg/ml vitamin C
Rice (untreated)	3.2	(0.2 mg/ml /15.1 ml) x 3.2 ml = 0.042  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.042 mg/ml In 100 g orange = (0.042/15) x 100                      = 0.280 mg/ml vitamin C
Rice (treated)	-	-
Broccoli (untreated)	12.7	(0.2 mg/ml /15.1 ml) x 12.7 ml = 0.168  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.168 mg/ml In 100 g orange = (0.168/15) x 100                      = 1.120 mg/ml vitamin C
Broccoli (treated)	7.5	(0.2 mg/ml /15.1 ml) x 7.5 ml = 0.099  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.099 mg/ml In 100 g orange = (0.099/15) x 100                      = 0.66 mg/ml vitamin C
Papaya (untreated)	15.1	(0.2 mg/ml /15.1 ml) x 15.1ml = 0.200  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.200 mg/ml In 100 g orange = (0.200/15) x 100                      = 1.33 mg/ml vitamin C
Papaya (treated)	11.4	(0.2 mg/ml /15.1 ml) x 11.4 ml = 0.151  mg/ml vitamin C in food sample Extract = 50 g + 100 ml In 30 ml extract =  (50/100) x 30 =15 g orange In 15 g orange = 0.151 mg/ml In 100 g orange = (0.151 /15) x 100                      = 1.01 mg/ml vitamin C

Magic writing

Discussion:

Measuring vitamin C using starch – iodine test (Project)

In this experiment solution containing food samples was titrated with an iodine solution in order to determine the amount of vitamin C in the food samples including beverage. The food samples that are used in this experiment are papaya, orange, broccoli, chrysanthemum, rice and ice cream soda (brought from home).

From the experiment, the food sample that contain the most vitamin C is chrysanthemum (treated) which is 2.87 mg/ml. The second highest amount of vitamin C is orange (untreated). Papaya also had more amount of vitamin C compared to broccoli and rice. The food sample that contain the lowest amount of vitamin C is rice which is 0.280 mg/ml this is because rice contain more carbohydrate than vitamin C. Ice cream soda had the second lowest amount of vitamin C. Fruits and vegetable samples contain higher amount of vitamin C.

The treated food samples are put in the water bath at 95 . From the result, we can see that chrysanthemum that was treated has high amount of vitamin C compared to untreated. According to Njoku, Ayuk, & Okoye (2011) the lower the temperature the better the concentration of Vitamin C in fruit juice. Higher temperature does not favour Vitamin C. That means higher temperature will reduce the amount of vitamin C in food samples. So, there are some errors occurred in our experiment. The amount of vitamin C in orange (untreated) is higher than orange (treated) which is 1.46 mg/ml and 1.34 mg/ml respectively. Amount of vitamin C for broccoli (untreated) also higher than broccoli (treated) which is 1.12 mg/ml and 0.66 mg/ml. Papaya also has higher amount of vitamin C for untreated (1.33 mg/ml) compared to treated (1.01 mg/ml). While, we cannot determine the amount of vitamin in rice (treated). This is because the rice became cooked rice in higher temperature.

When we compare the amount of vitamin C from the data obtained, we found that the amount of vitamin C are incorrect with the actual one. The actual amount of vitamin C is around 50 mg/ml. This also happens to other food samples such as papaya, broccoli and so on. From the actual amount of vitamin C, broccoli has the highest amount of vitamin C.

Errors that occurred in this experiment are hard to determine the end point of the titration for example like chrysanthemum and the samples also contaminated because we share the cloth filter.

Magic writing.

In this experiment, we used lemon juice as ink write the message in the paper. Iodine solution is used to detect the message on the paper. Then, we can see the message that was written on the paper which is white colour is formed and the paper turns blue because paper contains starch. Lemon juice contains vitamin C which prevents the reaction between starch and iodine to react.

Questions and answer:

        i.            What juices or drinks had the most vitamin C?

Juices had the most vitamin C.

      ii.            Did the drinks have the vitamin C that they advertised on the labels?

No.

    iii.            What food sources had the most vitamin C?

From the result obtained chrysanthemum had the most vitamin C.

    iv.            What families or groups had the most vitamin C?

Families or groups that had the most vitamin C are chrysanthemum, orange and broccoli.

      v.            Did plants that you do not normally eat have vitamin C?

Yes.

    vi.            Did heat affect the vitamin C content of food?

Yes.

  vii.            Did heat increase or decrease the vitamin C levels?

The heat will reduced the content of the vitamin C in food.

viii.            What way of food preparation would be the most nutritious?

Boiling. Boiling is quick, easy, and needs nothing but water and add salt. Boiling could be the best way to preserve nutrients in vegetables such as broccoli.

    ix.            Do you have any ideas now to get more vitamins from your meals?

Yes. Eat more vegetables and fruits to get enough vitamin without eating supplement.

Conclusion:

            As conclusion, amount of vitamin C in chrysanthemum (treated) is higher compared to the other food samples. Whereas, rice had the lowest amount of vitamin C. Most of the treated food samples have less amount of vitamin C compared to untreated except for chrysanthemum. For the magic writing, white colour of message will form on the paper when iodine react with lemon juice. It prevent the iodine to react with the paper that contains starch.

References:

Njoku, P. C., Ayuk, A. A., & Okoye, C. V. (2011). Temperature effects on vitamin C content in citrus fruits. Pakistan Journal of Nutrition, 10(12), 1168-1169.

Suntornsuk, L., Gritsanapun, W., Nilkamhank, S., & Paochom, A. (2002). Quantitation of vitamin C content in herbal juice using direct titration. Journal of pharmaceutical and Biomedical Analysis, 28(5), 849-855.

Gil, M. I., Tomás-Barberán, F. A., Hess-Pierce, B., & Kader, A. A. (2002). Antioxidant capacities, phenolic compounds, carotenoids, and vitamin C contents of nectarine, peach, and plum cultivars from California. Journal of Agricultural and Food Chemistry, 50(17), 4976-4982.

Reflection:

Heidi:

From this experiment, we determined the amount of vitamin C in food samples. Different type of food samples have different amount of vitamin C. Usually fruit and vegetable have high  amount of vitamin C compared to other food samples. Some problems happen during the experiment for example but we able to handle it. Then, the most interesting part is magic writing or invisible ink. We used lemon juice to write message in paper and put it in iodine solution to see the result. last but not least, we have a great teamwork during conducting the experiment.

Maureen:

This experiment is quite interesting for me especially the magic writing experiment. In this experiment,we used lemon and a piece of paper. Due to reaction of iodine on starch(paper), the  paper turns blue and the writing appeared.  From this experiment, I also find that the vegetables and fruit have high amount of Vitamin C compared to other food samples. The problems that we faced in this experiment is that the limitation of apparatus that the flow of experiment become slow.

Awanis:

From my point of view, I enjoyed doing the magic writing because at first, the writing does not show. But when we immersed the paper with writing on it into iodine solution, the writing showed itself. This is my first time doing this kind of experiment. As for the titration, we used ice cream soda that we bought to compare the result with another substance. Overall, this experiment need me to be precise in looking at the colour changed in the titration.