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Experiment 6.1

This experiment aims to compare the rates of fermentation of apple, orange, and carrot juices. Sugars in the fruit and vegetable juices like sucrose, glucose, and fructose undergo fermentation in the presence of enzymes invertase and zymase, producing ethanol and carbon dioxide. Samples from the reaction mixtures will be tested with Fehling's solution at regular intervals; the completion of fermentation is indicated when no further reaction (color change or precipitate) is observed with Fehling's solution. The rates of fermentation of the different juices will then be compared.

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113 views4 pages

Experiment 6.1

This experiment aims to compare the rates of fermentation of apple, orange, and carrot juices. Sugars in the fruit and vegetable juices like sucrose, glucose, and fructose undergo fermentation in the presence of enzymes invertase and zymase, producing ethanol and carbon dioxide. Samples from the reaction mixtures will be tested with Fehling's solution at regular intervals; the completion of fermentation is indicated when no further reaction (color change or precipitate) is observed with Fehling's solution. The rates of fermentation of the different juices will then be compared.

Uploaded by

sism
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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EXPERIMENT 6.

1
AIM: To compare the rates of fermentation of the following fruit / vegetable
juices:
Apple juices;
Orange juice;
Carrot juice.

THEORY:
The Objective of this project is to study the rates of fermentation of the
following fruit or vegetable juices.
i. Apple juice
ii. Carrot juice

Introduction

Fermentation is the slow decomposition of complex organic compound into


simpler compounds by the action of enzymes. Enzymes are complex organic
compounds, generally proteins. Examples of fermentation are: souring of milk
or curd, bread making, wine making and brewing.
The word Fermentation has been derived from Latin (Fervor which means to
‘boil’).As during fermentation there is lot of frothing of the liquid due to the
evolution of carbon dioxide, it gives the appearance as if it is boiling. Sugars
like glucose and sucrose when fermented in the presence of yeast cells are
converted to ethyl alcohol. During fermentation of starch, starch is first
hydrolyzed to maltose by the action of enzyme diastase. The enzyme diastase is
obtained from germinated barley seeds. Fermentation is carried out at a
temperature of 4–16 °C (40–60 °F). This is low for most kinds of fermentation, but
is beneficial for cider as it leads to slower fermentation with less loss of delicate
aromas. Apple based juices with cranberry also make fine ciders; and many
other fruit purées or flavorings can be used, such as grape, cherry, and
raspberry. The cider is ready to drink after a three month fermentation period,
though more often it is matured in the vats for up to two or three years.

History of Fermentation

Since fruits ferment naturally, fermentation precedes human history. Since


ancient times, however, humans have been controlling the fermentation
process. The earliest evidence of winemaking dates from eight thousand Years
ago in Georgia, in the Caucasus area. Seven thousand years ago jars containing
the remains of wine have been excavated in the Zagros Mountains in Iran,
which are now on display at the University of Pennsylvania. There is strong
evidence that people were fermenting beverages in Babylon circa 5000 BC,
ancient Egypt circa 3150 BC, pre-Hispanic Mexico circa 2000 BC and Sudan
circa 1500 BC.There is also evidence of leavened bread in ancient Egypt
circa1500 BC and of milk fermentation in Babylon circa 3000 BC. French
chemist Louis Pasteur was the first known zymologist, when in 1854 he
connected yeast to fermentation. Pasteur originally defined fermentation as
“respiration without air”.

Louis Pasteur in 1860 demonstrated that fermentation is a purely physiological


process carried out by living micro-organism like yeast. This view was
abandoned in 1897 when Buchner demonstrated that yeast extract could bring
about alcoholic fermentation in the absence of any yeast cells. He proposed that
fermenting activity of yeast is due to active catalysts of biochemical origin.
These biochemical catalyst are called enzymes. Enzymes are highly specific. A
given enzyme acts on a specific compound or a closely related group of
compounds. Fermentation has been utilized for many years in the preparation
of beverages. Materials from Egyptian tombs demonstrate the procedures used
in making beer and leavened bread. The history of fermentation, whereby
sugar is converted to ethanol by action of yeast, is also a history of chemistry.
Van Helmont coined the word iogaslt in 1610 to describe the bubbles produced
in fermentation. Leeuwenhoek observed and described the cells of yeast with his
newly invented microscope in 1680. The fruit and vegetable juices contain
sugar such as sucrose, glucose and fructose. These sugars on fermentation in the
presence of the enzymes invertase and zymase give with the evolution of
carbon dioxide. Maltose is converted to glucose by enzyme maltose. Glucose is
converted to ethanol by another enzyme zymase Invertase

𝑖𝑛𝑣𝑒𝑟𝑡𝑎𝑠𝑒
C12H22O11 + H2O → C6H12O6 + C6H12O6
Sucrose Glucose Fructose

𝑍𝑦𝑚𝑎𝑠𝑒
C6H12O6 + C6H12O6 → 2C2H5OH + 2CO2
Glucose Fructose Ethanol Diastase

𝐴𝑚𝑦𝑙𝑎𝑠𝑒
2(C6H1005) n +nH20 → nC12H22O11
Starch Maltose
C12H22O11 + H2O → 2C6H12O6
𝑀𝑎𝑙𝑡𝑎𝑠𝑒
Maltose Glucose

C6H12O6 → 2C2H5OH + 2CO2


Glucose Ethyl alcohol

Glucose is a reducing sugar and gives red coloured precipitates with


Fehling’s solution, when warmed. When the fermentation is complete, the
reaction mixture stops giving any red colour or precipitate with Fehling
solution.

The processes of fermentation can be studied because glucose and


fructose are reducing sugar and gives red coloured precipitate with Fehling's
solution when warmed. This means when the fermentation is complete, no red
colour or precipitate will be obtained with Fehling's solution.

MATERIALS REQUIRED:
A. Apparatus: Beakers, water bath, test tubes.
B. Chemicals: 1.Apple juice,
2. Orange juice,
3. Carrot juice,
4. Fehling solution A,
5. Fehling solution B,
6. distilled water.
7. Pasteur salt solution (1g ammonium titrate + 0.2g potassium
phosphate + 0.02g calcium
8. Phosphate + 0.02 Mg SO + 100 mL water).

PROCEDURE:
1. Take 10 mL of apple juice in a beaker. Dilute it to about 100 mL with
distilled water.
2. Add 2g Baker's yeast and 10 mL solution of Pasteur's salt to the above
juice solution.
3. Mix the contents thoroughly and keep the contents in the thermostat
maintained at 35 - 40 C.
4. After 10 minutes take out 5 drops of the mixture and add to 5 mL of
Fehling reagent in a test tube. Place the test tube in a boiling water bath
from about 2 minute and note the colour of the solution/ppt.
5. Repeat step 4 after every 10 minutes till reaction mixture gives no
colour/ppt with Fehling reagent.
6. Repeat steps 1-5 with carrot juice as well as with orange juice.

OBSERVATION:

RESULT:
The rate of fermentation of .......... juice is faster than of........ Juice and .........
juice.

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