chem project presentation
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presentationTRANSCRIPT
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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+
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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
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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
http://www.mratcliffe.com/images/vcb.pdfhttp://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.livestrong.com/article/424994-vitamin-c-dosage-per-day/http://www.mratcliffe.com/images/vcb.pdf -
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THNK
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