QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
Assignment title
QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
Submitted by
Talha Saeed
Roll # 37
Faisal Iftikhar
Roll # 18
B.Sc. (Hons) Food Science and Technology
6thSemester (Regular)
Subject
FST – 507 Sugar Technology
Submitted to
Mam AMMARA AINEE
Lecturer
Institute of Food Science and Nutrition (IFSN)
University of Sargodha, Sargodha
INSTITUTE OF FOOD SCIENCE AND NUTRITION (IFSN)
UNIVERSITY OF SARGODHA
SARGODHA
FST-507 Sugar Technology
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QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
In sugarcane the most abundant sugar present is sucrose. Sucrose is a disaccharide
which is made by the condensation of glucose and fructose.
Types Of Sugars In Sugarcane
There are two types of sugars present in sugarcane. Those are as under:
1) Reducing Sugars
2) Non-Reducing Sugars
1) Reducing Sugars
Reducing sugars are sugars which have free aldehyde or ketone group. These sugars
can react with other compounds and provide electrons to them. i.e glucose, maltose,
lactose, galactose, glyceraldehyde and many others.
2) Non-Reducing Sugars
Non-reducing sugars are sugars which don’t have free aldehyde or ketone group. i.e
sucrose and trehalose.
Principle and Reagents
Free aldehyde and ketone groups have the capability to change the color of copper
solution to brick red and make it insoluble cuprous oxide. Sugar contents in food sample are
estimated by determining the volume of sugar solution required to completely reduce the
measured volume of Fehling’s solution.
Copper Sulphate Solution (Fehling ‘A’)
Copper sulphate (69.28g) was dissolved in distilled water in 1 lit. volumetric flask and
makeup the volume to one liter solution. It is stored an amber colored bottle.
Alkaline Tartarate Solution (Fehling ‘B’)
Rochelle Salt (Potassium Sodium Tartarate) 346g and 100g sodium hydroxide were
dissolved in one liter volumetric flask and final volume was made upto one liter with distilled
water. It is also stored in an amber colored bottle. This solution keeps Cu2+ ions in solution
form.
Methyl Blue Indicator
1g of methyl blue was mixed with distilled water to make up the volume up to 100ml.
Phenolphthalein Indicator
1g of dye dissolved in ethanol to make up the volume up to 100ml.
FST-507 Sugar Technology
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QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
DETERMINATION OF REDUCING SUGARS
Reducing sugars that are present in sugarcane juice are glucose and fructose. To
determine reducing sugars following procedure is adopted:
At first a sample of 10 ml sugarcane juice is taken, phenolphthalein indicator is added
and titrated against 0.1 N NaOH. Once the neutralization completes add citric acid to clear
the solution. Fehling solution is alkaline in nature and in order to titrate it with sugar solution
we add citric acid. Apart from this, citric acid keeps the Cu2+ ions in available form. Distilled
water is added to make the volume of solution up to 100ml. Now 5ml Fehling A solution and
5ml Fehling B solution are added together and heated till boiling occurs. At this moment fill
the neutralized solution in burette. Add 2-3 drops of methylene blue indicator in the Fehling
mixture and again start heating along with constant titration till end point, brick red is
considered as an end point for this titration. Note the volume of neutralized solution used for
titration. Reducing sugars reduces Cu2+ to Cu1+ that gives brick red color. Upon heating CuO
and NaOH present in fehling solution dissociate that are responsible for this reaction:
2CuO
⇋
2Cu2+ + O2
NaOH
⇋
Na+ + OH-
Glucose Reaction
+ 2Cu2+ + 5OH
-
→
+ Cu2O + 3H2O
Fructose Reaction
+2Cu2+ +5OH
FST-507 Sugar Technology
-
→
+ CH2O + 3H2O
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QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
DETERMINATION OF TOTAL SUGARS
During the determination of total sugars the non-reducing sugars present in solution
are inverted/ converted to reducing sugars by the action of citric acid and then above methods
with some changes are used for determination of total sugars. The proper method for the
determination of total sugars is as follow:
First of all take 10ml sugarcane juice and add approximately 5gm citric acid (amount
may vary) is added with 10 min boiling or leave the juice for 7 days. If citric acid is not
available then HCl may be used for this. This addition of acid cause acid hydrolysis of
sucrose and convert it into glucose and fructose.
C12H22O11 +H+ + H2O
→
C6H12O6
+
H+ (Inversion of Sucrose)
Citric Acid Dissociation
H3C8H5O7 + 3H2O
3H3O+
⇋
⇋
3C6H5O7 + 3H3O+
3H2O + 3H+
After 7 days or boiling cool it and add phenolphthalein indicator and titrate it with
0.1N NaOH till end point. Once end point reaches dilution is done in order to make 100ml
solution. Burette is filled with the diluted solution. Prepare mixture by adding 5ml fehling A
and 5ml fehling B solution and heating till boiling. Once boiling starts add 2-3 drops of
methylene blue indicator and start titrating it with solution present in burette. Titrate with
constant heating till end point (brick red) and note the volume of solution used for titration.
Calculation
The formula used for the determination of sugars is
Total sugars or Reducing Sugars = 0.051 x Dilution factor x 100/Titrateable Volume
Dilution factor = Final volume of solution after dilution/ volume of actual sample taken.
Non Reducing Sugars = Total Sugars – Reducing Sugars
It should be noted that results would be in percentages always.
Other way to find non reducing sugar is its determination with the help of “High
Performance Liquid Chromatography” and “Gass Chromatography”.
FST-507 Sugar Technology
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QUANTITATIVE TEST (CHEMICAL) FOR SUGARS IN SUGARCANE
Disadvantages Of Chemical Method
Some of the disadvantages of chemical method are as under:
I.
The results depend on the precise reaction times, temp and reagent conc. → must be
carefully controlled.
II.
Cannot distinguishing bet different types of reducing sugar.
III.
Cannot directly determine of non-reducing sugars.
IV.
Susceptible to interference from other types of molecules that act as reducing agents.
FST-507 Sugar Technology
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