chem project presentation

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Vitamin C Content

in Commercial Orange Juice ofDifferent Brands

Group membersSarah LeeCrystal Tan Hui YeeNurul ElyanaMelissa Fong

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AbstractAimTo determine the Vitamin C content infour different brands of commercial orange juices,

Results Marigold :21.50mg (0.09%),Sunkist; 13.59mg (0.05%)Tropicana Twister; 7.40vitamin C mg (0.03%)

Fresh & Squeeze; 4.22mg (0.02%).We concluded that different brands of

orange juices have different content of

vitamin C!

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Introduction and background

Vitamin C or ascorbic acid is an organic

compound with molecular formula

C6H8O6.

In the manufacturing process, additional

ascorbic acid is often added to restore

nutrient losses during processing andpackaging.

As an antioxidant, ascorbic acid improve

the colour and palatability of many kinds

of food products.

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TH ORY The vitamin C content indifferent brands of

commercial orange juices

can be determined bytitration

The iodate ions are reduced to form iodine:

IO3+ 6H++ 5e I2+ 3H2O

The iodide ions are oxidised to form iodine:

2 I I2+ 2e-

Reaction between iodate and iodide ions:IO3

+ 5I+ 6H+ 3I2+ 3H2O

Iodine is reduced to iodide ions:

C6H8O6+ I2+ 2H2O ---> C6H10O8+ 2I-

+ 2H+

-

Potassium iodate is titrated against a solutioncontaining Vitamin C and potassium iodide

Iodine is prepared in-situ:

Iodine oxidises the ascorbic acid to dehydroascorbic acid:

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IO3 + 5I+ 6H+ 3I2+ 3H2OEquation 1

C6H8O6+ I2+ 2H2O ---> C6H10O8+ 2I-+ 2H+ - Equation 2

Using Equation 1, the moles of iodineformed:

1 mol iodate: 3 mol iodine

Using Equation 2, the moles of vitamin Cfrom the amount of I2produced:

3 mol iodine: 3 mol Vitamin C

1 mol iodine: 1 mol Vitamin C

Mass of ascorbic acidper 25ml juice = x mg

% of Vitamin C= _____g/25ml x 100% = _____%

Molar mass of ascorbic acid, C6H8O6 = 176 g/mol

Calculations

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iterature reviewNagra S., Auckland

University of Technology

(2006):

Two methods were

adopted for determiningascorbic acid. The liquid

chromatography was less

successful than the simpler

titrimetric method.

D. Massaioli, P.R. Haddad

(1981) :

Ascorbic acid content

was found to decrease

slightly during storage,with the loss of ascorbic

acid dependent on the

handling method use.

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Problem statementWhat is the vitamin C content incommercial orange juiceof different brands?

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bjectives.

To determine the Vitamin C content in

four brands of commercial orange juices whichare Marigold, Sunkist, Tropicana Twister and Fresh

N Squeeze by iodometric titration.

To compare the vitamin C content among the fourdifferent brands of orange juices.

To promote awareness on consumer products and

healthy living.

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.

h d l

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Methodology, Apparatus &materials

50ml burette,

20ml pipette,

100ml measuring cylinders,

retort stand and clamp,

250ml conical flasks,

100ml beakers,

filter funnel,

electronic balance

Orange juices of 3-4 brands,

0.001M potassium iodate solution

1.0 g potassium iodide,

starch indicator solution,

1.0M hydrochloric acid

d

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Procedure:Strain the pulp in the juice

Conical flask: Pipette 25ml of juice .Add 1g KI, 5ml HCl, 2-3ml starch solution

Burette: Fill with potassium iodate solution.

Record the initial burette reading

Titrate potassium iodate with the solution in the flask.

Swirl gently.

Calculate the amount of Vitamin C.

Record the results in a table

Stop titrating when theres noticeable colour change.

Record the final burette reading.

Repeat to obtain average volume.

Repeat with the other 3 juices

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Results,

Observations &Discussion

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Type of Orange

Juice

Initial

Reading(cm3)

Average

Reading(cm3

Average volume

of KIO3added

(cm3)

Marigold 0.00 41.00 41.00

Fresh & Squeeze 0.00 8.25 8.25

Sunkist 0.00 25.93 25.93

Tropicana 0.00 14.10 14.10

Burette reading for the different brands of Orange Juice

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Observations & Discussions

Before endpoint, the colour of the solution was the

bright yellow colour of fresh orange juice.

Upon addition of potassium iodate, streaks of blue-black

colour where formed, but the colour disappeared quickly upon

swirling.Explanation: The iodine (I

2) formed in the conical flask is

still reacting with the ascorbic acid present in a 1:1 ratio.

At the titration endpoint, any excess iodate added

produced iodine which reacted with starch to form a

dark starch-iodine complex that persisted.

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Observations & Discussions

As the sample fruit juice is coloured, the colour change

visible was from yellowto brown-grey.

Hence, the intensityof the sample solution used affectedthe accuracy in the determination of the endpoint.

When 1-2ml more of iodate solution was added after the

endpoint was overshot,the dark blue complex becamemore obvious. This was taken as the rough readings.

Rough titration was carried out to determine

how much titrant (potassium iodate) was needed,so that the titration process of multiple samples could be

sped up.

Rough titration also helped to recognise the colour

change that occur at the endpoint.

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IO3 + 5I+ 6H+ 3I2+ 3H2OEquation 1

C6H8O6+ I2+ 2H2O ---> C6H10O8+ 2I-+ 2H+ - Equation 2

Volume of KIO3from burette used = 40.67cm3M =mol/dm30.001M = moles of KIO3/4.067x10

-2dm3

Moles of KIO3= 4.067 x 10-5mol

Using Equation 1, the moles of iodine formed:4.067 x 10-5moles of KIO3x 3moles I2/I mole KIO3= 1.2201 x 10

-4moles I2

Using Equation 2, the moles of vitamin C produced:

1.2201 x 10-4moles I2x 1 mole Vitamin C/1mole I2= 1.2201 x 10-4moles of Vitamin C

Molar mass of ascorbic acid, C6H8O6=176g/mol

Mass of ascorbic acid per 25ml juice = 1.2201 x 10-4x 176 = 0.0215g = 21.50mg

% of Vitamin C= 0.0215g/25ml x 100% = 0.09%

Results: Calculation

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Table 1: Average volume of KIO3reacted (cm3),

mass of ascorbic acid per 25ml juice (mg),

percentage of Vitamin C (%)

Brand Average

volume of

KIO3

reacted

(cm3)

Mass of

ascorbic acid

per 25ml juice

(mg)

Percentage of

Vitamin C in 25ml

juice (%)

Marigold 40.67 21.50 0.09

Fresh & Squeeze 8.00 4.22 0.02

Sunkist 25.73 13.59 0.05

Tropicana Twister 13.80 7.40 0.03

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Marigold has the highest amount of Vitamin C with 21.50mg

(0.09%), followed by Sunkist; 13.59mg (0.05%), Tropicana

Twister; 7.40mg (0.03%) and lastly, Fresh N Squeeze; 4.22mg

(0.02%).

0

0.02

0.04

0.06

0.08

0.1

MarigoldFresh N

SqueezeSunkist

Tropicana

Twister

0.09

0.02

0.05

0.03

Percentage of Vitamin C

G

R

A

P

H

P

E

R

C

E

N

T

A

G

E

O

F

V

I

T

A

MI

N

C

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Based on these results, the Vitamin C contents in MarigoldPeel Fresh Sunkist Tropicana Twister and Fresh N Squeezeare sufficient to meet the daily requirements which is 70mgof vitamin C per day for men and women above the age of 19(Ministry of Health of Malaysia 2005).

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However, consumers of brands with low Vitamin C contentwill have to take bigger and more frequent servingsof thejuice compared to consumers of brands with high Vitamin Ccontent.

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Conclusion From our experiment, we determined the Vitamin C content

in four brands of commercial orange juices: Marigold PeelFresh, Sunkist, Tropicana Twister and Fresh & Squeeze.

Marigold had the most Vitamin C while Fresh N Squeeze

had the least.

Future experiments could be carried out by the back-

titrationof excess iodine (I2) with thiosulphate (S2O3-). The

endpoint of titration is the disappearance of the blue-black

colour which is easier to identify.

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ReferenceHigdon, Jane. (January 31 12, 2006); Vitamin C; Linus Pauling

Institute-Oregon State University

Recommended Nutrient Intakes for Malaysia,(2005). National

Coordinating Committee on Food and Nutrition (NCCFN),

Ministry of Health Malaysia

http://www.mratcliffe.com/images/vcb.pdf; accessed on18/8/2013

http://www.livestrong.com/article/424994-vitamin-c-dosage-per-

day/; accessed on 18/8/2013

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THNK

Y

O

U