AIM:
TO COMPARE RATE OF FERMENTATION OF GIVEN
SAMPLE OF WHEAT FLOUR, GRAM FLOUR AND
POTATO.
INTRODUCTION:
Fermentation typically is the conversion of carbohydrates to
alcohols and carbon dioxide or organic acids using yeasts,
bacteria, or a combination thereof, under anaerobic conditions. A
more restricted definition of fermentation is the chemical
conversion of sugars into ethanol. The science of fermentation is
known as zymology. Fermentation usually implies that the action
of microorganism is desirable, and the process is used to produce
alcoholic beverages such as wine, beer and cider. Fermentation is
also employed in preservation techniques to create lactic acids in
sour foods such as sauerkraut, dry sausages, yoghurt or vinegar
for use in pickling foods.
HISTORY:
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 circa 1500 BC and of milk
fermentation in Babylon circa 3000 BC. French chemist Louis Pasteur
was the first knows zymologist, when in 1854 he connected yeast to
fermentation. Pasteur originally defined fermentation as “respiration
without air”.
Contributions to Bio-Chemistry:
When studying the fermentation of sugar to alcohol by yeast Louis
Pasteur concluded that the fermentation was catalysed by a vital force
called “ferments”, within the yeast cells. The “ferments” were thought
to function only with living organisms. “Alcoholic fermentation is an act
correlated with the life and organisation of the yeast cells, not with the
death or putrefaction of the cells,” he wrote. Nevertheless, it was
known that yeast cells. While studying this process in 1897, Eduard
Buchner of Humboldt University of Berlin, Germany, found that sugar
was fermented even when there were no living yeast cells in the
mixture by a yeast secretion that he termed zymase. In the 1907 he
received the Nobel Prize in Chemistry for his research and discovery of
“cell-free fermentation.” One year prior, in 1906, ethanol fermentation
studies led to the early discovery of NAD+ uses.
Food Fermentation has been said to serve five main
purposes:
1. Enrichment of the diet through development of a diversity of
flavours, aromas and textures in food substrates.
2. Preservatives of substantial amounts of food through lactic acid,
alcohol, acetic acid and alkaline fermentations.
3. Biological enrichment of food substrates with protein, essential
amino acids, essential fatty acids and vitamins.
4. Elimination of ant nutrients.
5. A decrease in cooking times and fuel requirements.
Risks of consuming fermented foods:
Food that is improperly fermented has a notable risk of exposing the eater to
botulism. Alaska has witnessed a steady increase of cases of botulism since 1985
Despite its small population, it
has more cases of botulism than any other state in the United States of America.
This is caused by the traditional Eskimo practice of allowing animal products such
as whole fish, fish heads, walrus, sea lion and whale flippers, beaver tails, seal oil,
birds, etc., to ferment for an extended period of time before being consumed. The
risk is exacerbated when a plastic container is used for this purpose instead of the
old-fashioned method grass-lined hole, as the botulinum bacteria thrive in the
anaerobic conditions created by the air-tight
enclosure in plastic.
Safety of Fermented Foods:
Fermented foods generally have a very good safety record
even in the developing world where the foods are
manufactured by people without training in microbiology
or chemistry in unhygienic, contaminated environments. They are
consumed by hundreds of millions of people every day in both the
developed and the developing world. And they have an excellent safety
record. What is there about fermented foods that contributes to safety?
While fermented foods are themselves generally safe, it should be
noted that fermented foods by themselves do not solve the problems of
contaminated drinking water, environments heavily contaminated with
human waste, improper personal hygiene in food handlers, flies
carrying disease organisms, unfermented foods carrying food poisoning
or human pathogens and unfermented foods, even when cooked if
handled or stored improperly .Also improperly fermented foods can be
unsafe. However, application of the principles that lead to the safety of
fermented foods could lead to an improvement in the overall quality
and the nutritional value of the food supply, reduction of nutritional
diseases and greater resistance to intestinal and other diseases in
infants.
THEORY:
Wheat flour, gram flour and potatoes contain starch as the major
constituent. Starch present in these food materials is first brought into
solution.in the presence of enzyme diastase, starch undergo
fermentation to give maltose.
Starch gives blue-violet colour with iodine whereas product
of fermentation starch do not give any characteristic colour.
When the fermentation is complete the reaction mixture stops giving
blue-violet colour with iodine solution.
By comparing the time required for completion of fermentation of
equal amounts of different substances containing starch the rates of
fermentation can be compared. The enzyme diastase is obtained by
germination of moist barley seeds in dark at 15-degree Celsius. When
the germination is complete the temperature is raised to 60 degree
Celsius to stop further growth. The seeds are crushed into water and
filtered. The filtrate contains enzyme diastase and is called malt extract.
MATERIALS REQUIRED: -
Conical Flask
Test Tube
Funnel
Filter Paper
Water Bath
1% Iodine solution
Yeast
Wheat Flour
Rice Flour
Potato
Aqueous NaCl solution.
PROCEDURE: -
1. Take 5 gm of wheat flour in 100 ml conical flask and add 30 ml of distilled
water.
2. Boil the contents of the flask for about 5 minutes.
3. Filter the above contents after cooling, the filtrate obtained is . . wheat
flour extract.
4. To the wheat flour extract. taken in a conical flask.
5. Add 5 ml of 1% aq. NaCl solution.
6. Keep this flask in a water bath maintained at a temperature of 50-60
degree Celsius. Add 2 ml of malt extract.
7. After 2 minutes take 2 drops of the reaction mixture and add to diluted
iodine solution.
8. Repeat step 6 after every 2 minutes. When no bluish colour is produced the
fermentation is complete.
9. Record the total time taken for completion of fermentation.
10.Repeat the experiment with gram flour extract, rice flour extract, potato
extract and record the observations.
OBSERVATIONS: -
Time Required for fermentation:
WHEAT FLOUR- 10 HOURS
RICE FLOUR-15 HOURS
POTATO-13 HOURS
CONCLUSION: -
Rice Flour takes maximum time for fermentation and Wheat Flour
takes minimum time for fermentation.
BIBLIOGRAPHY: -
Class XII Chemistry NCERT Textbook
Class XII NCERT Lab Manual Chemistry.
Wikipedia
Google
archiveworld.org/projects
