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Fermentation Based On
Fermentation is a term derived from the
latin verb fevere, (Same root
as effervescence), meaning to boil.
It an anaerobic cellular process in which
bacteria, yeast or other microorganisms
convert organic foods into simpler
compounds, and chemical energy(ATP) is
However in Food Processing, fermentation
has been generally described as the
conversion of carbohydrates into alcohols
and carbon dioxide or organic acids by
yeast, bacteria or a combination of both.
Sahlin(1999) defined fermented
foods as those foods which have been
subjected to the action of micro-
organisms or enzymes so that
desirable biochemical changes cause
significant modification to the food.
Fermented foods comprise about
one-third of the world wide
consumption of food and 20-40 %
(by weight) of individual diets.
Classification of Fermented Foods
Fruits and vegetables
Fermentation; An Ancient Tradition
Fermentation is one of the oldest forms of food preservation technologies
in the world.
The French chemist Louis Pasteur determined that fermentation is caused
by yeast. His work was influenced by the earlier work of Theodor
Schwann, the German scientist who helped develop the cell theory.
There is reliable information that fermented drinks were being produced
over 7,000 years ago in Babylon (now Iraq), 5,000 years ago in Egypt,
4,000 years ago in Mexico and 3,500 years ago in Sudan.
China is thought to be the birth-place of fermented vegetables and the
use of Aspergillus and Rhizopus moulds to make food.
Knowledge about traditional fermentation technologies has been handed
down from parent to child, for centuries. These fermented products have
been adapted over generations; some products and practices no doubt fell
by the wayside while others remained.
Food Approximate year of
Mushrooms 4000 BC China
Soy Sauce 3000 BC China, Korea and
Wine 3000 BC North Africa, Europe
Fermented Milk 3000 BC Middle East
Cheese 2000 BC Middle East
Beer 2000 BC North Africa, China
Bread 1500 BC Egypt, Europe
Fermented Meat 1500 BC Middle East
Sour Dough Bread 1000 BC Europe
Fish Sauce 1000 BC South East Asia
Pickled Vegetables 1000 BC China, Europe
Tea 500 BC China
A vegetable is a plant cultivated for food. They include edible parts such
as leaves, bulbs, stem and roots (Keller, 2012).
Vegetables are more prone to deterioration by micro-organisms and can
provide an ideal substrate for the multiplication of microorganisms. They
are preserved either through pickling, fermentation, salting, drying or
other methods (Mcfeeters et al., 2013).
Fermentation has been utilized for centuries to preserve these foods. As
early as the third century BC, the Chinese described the preservation of
vegetables by fermentation.
Vegetable fermentation is a technique whereby, starches and sugars in
vegetables are converted into lactic acid by lactic-acid-producing
Fermented vegetables are produced by relatively low technology
processes with low energy inputs and produce foods that have unique
flavors and textures also adding variety to the diet.
The lactic acid bacteria are a group of Gram positive bacteria, non-
respiring, non-spore forming, cocci or rods, which produce lactic acid as
the major end product of the fermentation of carbohydrates.
Some members of the family are homofermentative that is they only
produce lactic acid, while others are heterofermentative and produce lactic
acid plus other volatile compounds and small amounts of alcohol.
Historically, bacteria from the genera Lactobacillus, Leuconostoc,
Pediococcus and Streptococcus are the main species involved. Several more
have been identified, but play a minor role in lactic fermentations Soomoo et
Lactobacillus is very heterogeneous genus, encompassing species with a
large variety of phenotypic, biochemical, and physiological properties. Most
species of lactobacilli are homofermentative, but some are
Lactobacillus acidophilus, L. bulgaricus, L. plantarum, L. caret, L.
pentoaceticus, L brevis and L. thermophiles are examples of lactic acid-
producing bacteria involved in food fermentations.
Lactic Acid Bacteria
Species of the genera Streptococcus and Leuconostoc produce the least
acid. Next are the heterofermentative species of Lactobacillus which
produce intermediate amounts of acid, followed by the Pediococcus and
lastly the homofermenters of the Lactobacillus species, which produce
the most acid.
Homofermenters, convert sugars primarily to lactic acid, while
heterofermenters produce about 50% lactic acid plus 25% acetic acid
and ethyl alcohol and 25% carbon dioxide.
Specifically, Leuconostoc mesenteroides is a bacterium associated with
the sauerkraut and pickle fermentations. This organism initiates the
desirable lactic acid fermentation in these products. It differs from other
lactic acid species in that it can tolerate fairly high concentrations of salt
and sugar (up to 50% sugar).
Lactobacillus brevi Leuconostoc mesenteroides
Examples of Fermented Vegetable and Vegetable
Garlic Lactobacillus plantarum
Carrot Slices Lactobacillus sacei
Olive Lactobacillus pentosus
Cabbage, Gourd, Celery Lactobacillus plantarum, Lactobacillus
brevis, Lactobacillus pentosus
Cucumber Lactobacillus plantarum
Mixture of cabbage and carrot Mixed starter culture
Sauerkraut and Sauerkraut Juice Lactobacilus plantarum,, Lactobacillus
casei, Pediococcus pentosaccus
Cabbage Juice 16 Strains of Lactobacillus genera or
Lactobacillus, mixture culture
Lye-Treated Carrot Lactobacillus plantarum or mixture
culture, Lactobacillus plantarum and
Carrot Juice Lactobacillus plantarum and
Other Fermented Vegetables
Lactic acid fermentation of vegetables can be carried out under
four basic types of conditions:
1. Dry salted; With dry salting, the vegetable is treated with dry salt. The
salt extracts the juice from the vegetable and creates the brine. For every
100 kg of vegetables 3 kg of salt is needed E.g sauerkraut, dry salted
pickled cucumbers e.t.c
2. Brine Salted; Brine is used for vegetables which inherently contain less
moisture. A brine solution is prepared by dissolving salt in water (a 15
to 20% salt solution) E.g Pickled cucumbers, Kimchi, Olives, Raddish
3. Non-salted; Vegetables are fermented by lactic acid bacteria,
without the prior addition of salt or brine E.g Gundruk, Sinki,
Fermented tea leaves e.t.c
4. Pit- Fermentation
South Pacific pit fermentations are an
ancient method of preserving vegetables
without the addition of salt.
The raw materials undergo an acid
fermentation within the pit, to produce a
paste with good keeping qualities. Example
include Kawal i.e Leaves of Wild African
Legume called Cassia obtusifolia and
Cassava leaves –Ombolo wa Koba.
Sauerkraut is defined as the clean, sound
product of characteristic flavor, obtained by full
fermentation, chiefly lactic, of properly and
shredded cabbage in the presence of not less
than two percent or more than three percent of
salt ( Frazier and Westhoff, 2008).
The end products of a normal kraut fermentation
are lactic acid along with smaller amounts of acetic
and propionic acids, a mixture of gases of which
carbon dioxide is the principal gas, small amounts of
alcohol and a mixture of aromatic esters.
The acidity helps to control the growth of spoilage
and putrefactive organisms and contributes to the
extended shelf life of the product.
Shredded cabbage or other suitable vegetables are
placed in a jar and salt is added. Mechanical pressure
is applied to the cabbage to expel the juice, which
contains fermentable sugars and other nutrients
suitable for microbial activity.
The first micro-organisms to start acting are the gas-producing
cocci (L. Mesenteroides). These microbes produce acids. When
the acidity reaches 0.25 to 0.3% (calculated as lactic acid), these
bacteria slow down and begin to die off, although their enzymes
continue to function.
The activity initiated by the L. mesenteroides is continued by the
lactobacilli (L. plantarum and L. Cucumeris) until an acidity
level of 1.5 to 2% is attained. The high salt concentration and low
temperature inhibit these bacteria to some extent. Finally, L.
pentoaceticus continues the fermentation, bringing the acidity to
2 to 2.5% thus completing the fermentation.
Trouble Shooting Sauerkraut : Spoilage
White Film Safe
White Sludge Safe in Small Amounts
Unless coupled with slime.
Creamy Film Unsafe
Yeasty Odour Unsafe
Pink Cabbage Unsafe (Caused by Yeast)
Browned Cabbage Unsafe
Slime or Ropy Unsafe (Caused by encapsulated varieties of
• The cucumbers are submerged in the brine,
ensuring that none float on the surface. The
strong brine draws the sugar and water out
of the cucumbers, which simultaneously
reduces the salinity of the solution.
• A few days after the cucumbers have been
placed in the brine, the fermentation
process begins. The process generates heat
which causes the brine to boil rapidly.
Acids are also produced as a result of the
• The colour of the cucumber surface
changes from bright green to a dark olive
green as acids interact with the chlorophyll.
• The interior of the cucumber changes from
white to a waxy translucent shade as air is
forced out of the cells.
Spoilage Defects and Problems in Pickles
The production of excessive amounts of
acid during the fermentation, results in
shrivelling of the pickles, possibly due to
over-activity of the L. mesenteroides
Softening: Pectinolytic or cellulolytic
enzymes may be secreted by
Gaseous spoilage: One defect is termed
"bloaters" i.e. pickles that float on the brine
or are hollow or have large air spaces in
the interior due to formation of gas inside
Gundruk Gundruk is particularly popular in Nepal and is a
non-salted fermented vegetable product. Gundruk is
obtained from the fermentation of leafy vegetables
(Mustard, cauliflower and raddish) in Nepal.
Shredded leaves are tightly packed in an earthenware
pot and warm water (at about 30oC) is added to cover
all the leaves. The pot is then kept in a warm place.
After five to seven days, a mild acidic taste indicates
the end of fermentation and the gundruk is removed
Pediococcus and Lactobacillus species are the
predominant microorganisms responsible for Gundruk
The fermentation is initiated by L. cellobiosus and L.
plantarum, and other homolactics make a vigorous
growth from the third day onwards. Pediococcus
pentosaceus increases in number on the fifth day and
thereafter declines .
Wilt for One to Two Days
Place tightly in an earthen Pot
Cover Leaves (The pot is kept Warm in the
sun and by a fire at Night
Add warm water
Products are dried on mats
Sunki is a non-salted fermented vegetable product
prepared from the leaves of "Otaki-turnip" in Kiso
district, Nagano prefecture, Japan. Sunki is eaten
with rice and in miso soup.
The Production Process
The Otaki-turnip is boiled, inoculated with "Zumi"
(a wild small apple) and dried Sunki from the
previous year and allowed to ferment for one to two
Sunki is produced under low temperature (in winter
season). Micro-organisms involved include
Lactobacillus plantarum, L. Brevis, Bacillus
coagulans and Pediococcus pentosaceus .
Sinki ( Pickled Raddish)
Sinki is a non-salted fermented
sour pickle prepared from radish
tap roots. It is consumed
traditionally in India, Nepal and
parts of Bhutan, where it is used as
a base for soup or eaten as a pickle.
It is one of the most popular
pickles in Nepal.
Fresh radish roots are harvested, washed and wilted
by sun-drying for one to two days.
They are then shredded, re-washed and packed
tightly into an earthenware or glass jar, which is
sealed and left to ferment.
The optimum fermentation time is twelve days at
30ºC. Sinki fermentation is initiated by L.
fermentum and L. brevis, followed by L. plantarum.
During fermentation the pH drops from 6.7 to 3.3.
After fermentation, the radish substrate is sun-dried
to a moisture level of about 21%.
There is a second processing method involving
fermentation in a clay lined pit for two to three
For consumption, sinki is rinsed in water for two
minutes, squeezed to remove the excess water and
fried with salt, tomato, onion and green chilli.
Fried mixture is then boiled in rice water and
served hot as soup along with the main meal.
Kawal is a strong smelling Sudanese,
protein-rich food prepared by
fermenting the leaves of a wild African
legume, Cassia obtusifolia and is usually
cooked in stews and soups.
It is used as a meat analogue. Its protein
is of high quality, rich in sulphur amino
It is a pit fermented vegetable product
All the stems, pods and flowers are removed.
The leaves are not washed, since it is thought
that natural micro-organisms on the leaves are
important for the correct fermentation.
The leaves of the leguminous plant are
pounded into paste without releasing the juice.
The paste is placed in an earthenware jar and
covered with sorghum leaves.
The whole jar is sealed with mud and buried
in the ground up to the neck in a cool place.
Every three days the contents are mixed by
The fermentation takes about fourteen days.
The fermentation is extremely complex.
The main micro-organisms are Bacillus
subtilis and Propionibacterium spp. Lactic acid
bacteria including Lactobacillus plantarum;
yeasts including Candida
krusei and Saccharomyces spp and moulds
including Rhizopus spp are also involved.
Select Leaves, remove stems and flowers
Pound the leaves into a paste using a mortar and
Place in a jar covered with sorghum leaves
Bury the jar in the pit up to the neck
Mix Every three Days
After Fermentation, Roll into balls.
Korean Kimchi is a brine salted fermented
Korean people consume 50-500 g/day of
kimchi, a fermented blend of radishes,
turnips, onions, and Chinese
cabbage. Sweet or sour peppers are often
included to provide additional flavor.
15% brine is used in
the fermentation which occurs at
Lactic acid bacteria is responsible
for this fermentation include L.
mesenteroides, S. faecalis, L. brevis,
L. plantarum, and P. cerevisiae.
Because the ingredients do not
contain so much sugar, the final
pH is 4.2-4.5 (0.8% total acidity).
Ombolo wa koba
In Zaire (Congo) cassava leaves are fermented to
produce ombolo wa koba which is traditionally eaten with boiled
cassava and plantain bananas.
Cassava leaves are allowed to wilt and turn black. This takes
about three to four days.
The cassava leaves are then chopped up and placed in a pot of
boiling water for about one hour.
During this processing stage, a water soluble extract of ash is
produced by placing the ash of burnt dried banana skins and
palm tree flowers in a strainer and pouring water through it.
The extract is then added to the boiled cassava leaves. The
extract is alkaline and neutralizes the cyanhydric acid liberated
when the leaves are chopped up. Salt and dried fish or meat is
After allowing the cassava leaf mixture to cool a little, acid palm
oil is then added. This reacts with the excess alkali and
neutralises it. The product is now ready to be eaten
Importance of Fermented Vegetables
• Enrichment of food substrates biologically with vitamins and other
• Enrichment of the human diet through development of a wide
diversity of flavors, aromas and textures in food.
• Increase digestibility of Vegetables
• Preservation of substantial amounts of vegetables
• Reduce Anti nutritional Properties in Vegetables during the
A decrease in cooking times and fuel requirements
There are many traditional beliefs about the medicinal properties of
fermented food products. The Fur ethnic group in Sudan strongly
believe that the consumption of fermented foods protects them from
However, There are some scientific basis to these assertions includes:
• The lowering of the pH inhibits the growth of food spoiling or
poisoning bacteria and destroys certain pathogens.
• Certain lactic acid bacteria (e.g. Lactobacillus acidophilus) and
moulds have been found to produce antibiotics and bacteriocins .
• The beneficial health effects of lactic acid bacteria on the intestinal
flora are well documented.
• Substances in fermented foods have been found to have a
protective effect against the development of cancer.
Indigenous Fermented Vegetables: Future Outlook and Recommendations
Because of the tremendously important role indigenous fermented
vegetables play in food preservation and their potential to contribute to
the growing food needs of the world especially in Africa, Latin America,
it is essential that the knowledge of their production is not lost and
various improvements are made.
The potential areas for improvement of fermented vegetable products are;
• Improve the understanding and product awareness of fermented
• Refine the processes
• Disseminate the improvements
• Create a supportive policy environment.
Improve the understanding and product awareness of indigenous fermented vegetables
Documenting the traditional knowledge to ensure that the huge
diversity is not lost
Developing a scientific understanding of the microbial processes,
with a view to improving the efficiency of the process. This can be
I. The isolation and characterization of the essential micro-
II. The investigation of the effects of pre-treatments of raw materials
on the fermentation process
III. The identification of the options for further processing and how
these affect the taste and texture of the product.
Refining the process
The commercially produced products, such as sauerkraut, pickles
are all examples of processes which have been studied and
Refining of the process for indigenous fermented vegetables can
be achieved through
1. Process Control
• The selection or development of more productive microbial
• The control and manipulation of culture conditions
• The improvement of product purification and concentration.
• Development of pure starter cultures.
2. Quality Control
The sort of areas that should be investigated include:
Selecting good quality raw materials
Processing under correct conditions
Ensuring high standards of personal hygiene by the food
Ensuring the processing area is sufficiently clean
Using correct packaging
• Vegetable Fermentation is a desirable process and used as vital tool
for preservation of vegetable which are highly perishable. This
practice dates back to thousands of Years ago in China.
• Fermented products have desirable characteristics such as flavor,
improved nutritional quality i.e. Nutrient composition, increase in
digestibility, removal of anti nutritional factors etc.
• Most traditionally fermented vegetables have remained largely
untapped in parts of the world such as Africa, latin America e.t.c
• Adequate investment into research and scientific studies should be
made so as to commercialize these products.
• Examples of Products already consumed largely are sauerkraut,
pickled vegetables e.g. cucumber, pepper, olives e.t.c Lactic acid
bacteria are the major microorganisms involved in the fermentation
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