Foods that have been subjected to the action of
micro-organisms or enzymes, in order to bring
about a desirable change.
Numerous food products owe their production and
characteristics to the fermentative activities of
Fermented foods originated many thousands of
years ago when presumably micro-organism
contaminated local foods.
Micro-organisms cause changes in the foods which:
› Help to preserve the food,
› Extend shelf-life considerably over that of the
raw materials from which they are made,
› Improve aroma and flavour characteristics,
› Increase its vitamin content or its digestibility
compared to the raw materials.
Table 1 History and origins of some fermented foods
Food Approximate year
China, Korea, Japan
North Africa, Europe
North Africa, China
Southeast Asia, North Africa
The term “biological ennoblement” has
been used to describe the nutritional
benefits of fermented foods.
Fermented foods comprise about one-
third of the world wide consumption of
food and 20- 40 % (by weight) of
Table 2 Worldwide production of some fermented foods
Food Quantity (t) Beverage Quantity (hl)
Table 3 Individual consumption of some fermented
foods: average per person per year
Soy sauce (I)
Table 4 Benefits of fermentation
Enhancement of safety
Acid and alcohol production
Production of bacteriocins
Removal of toxic components
Gari, polviho azedo
Enhancement of nutritional value
Retention of micronutrients
Increased fibre content
Synthesis of probiotic compounds
Nata de coco
Bifidus milk, Yakult,
Improvement of flavour Coffee beans
Fresh cassava contains cyanhydric acid (HCN)
that should be eliminated from any product
originating from cassava to render it fit for
human consumption. Depending on the
production method (particularly traditional
methods) gari could contains up to 20 mg / kg of
HCN - against 43 mg / kg for fresh peeled
Gari is a fermented, gelled and dehydrated food
produced from fresh cassava. It is a popular diet
in Nigeria, Benin, Togo, Ghana and in other West
Africa's countries. The consumption area even
expands to Central Africa: Gabon, Cameroon,
Congo Brazzaville and Angola.
Polvilho is a fine tapioca/manioc/cassava flour. it
can be found at latino markets in california as
"sour starch" (polvilho azedo) or "sweet starch"
A high fiber, zero fat Philippino dessert.
A chewy, translucent, jelly-like food
product produced by the bacterial
fermentation of coconut milk.
Commonly sweetened as a candy or
dessert, and can accompany many
things including pickles, drinks, ice cream,
and fruit mixes.
Highly regarded for its high dietary fiber,
and its zero fat and cholesterol content.
It is produced through a series of steps
ranging from milk extraction, mixing,
fermentation, separating, cleaning,
cutting to packaging.
Major group of Fermentative organisms.
This group is comprised of 11 genera of gram-positive
Carnobacterium, Oenococcus, Enterococcus,
Pediococcus, Lactococcus, Streptococcus,
Lactobacillus, Vagococcus, Lactosphaera, Weissells
Related to this group are genera such as Aerococcus,
Microbacterium, and Propionbacterium.
While this is a loosely defined group with no precise
boundaries all members share the property of producing
lactic acid from hexoses.
As fermenting organisms, they lack functional heme-linked
electron transport systems or cytochromes, they do not
have a functional Krebs cycle.
Energy is obtained by substrate-level phosphorylation
while oxidising carbohydrates.
The lactic acid bacteria can be divided into two groups
based on the end products of glucose metabolism.
Those that produce lactic acid as the major or sole
product of glucose fermentation are designated
Those that produce equal amounts of lactic acid, ethanol
and CO2 are termed heterofermentative.
The homolactics are able to extract about twice as much
energy from a given quantity of glucose as the
All members of Pediococcus, Lactococcus,
Streptococcus, Vagococcus, along with some
lactobacilli are homofermenters.
Carnobacterium, Oenococcus, Enterococcus,
Lactosphaera, Weissells and Lecconostoc and some
Lactobacilli are heterofermenters
The heterolactics are more important than the
homolactics in producing flavour and aroma
components such as acetylaldehyde and diacetyl.
The lactic acid bacteria are mesophiles:
› they generally grow over a temperature
range of about 10 to 40o
› an optimum between 25 and 35o
› Some can grow below 5 and as high as 45
Most can grow in the pH range from 4 to 8. Though
some as low as 3.2 and as high as 9.6.
Traditionally the fermenting organisms came from the
natural microflora or a portion of the previous
In many cases the natural microflora is either inefficient,
uncontrollable, and unpredictable, or is destroyed
during preparation of the sample prior to fermentation
A starter culture can provide particular characteristics in
a more controlled and predictable fermentation.
Lactic starters always include bacteria that convert
sugars to lactic acid, usually:
› Lactococcus lactis subsp. lactis,
› Lactococcus lactis subsp. cremoris or
› Lactococccus lactis subsp. lactis biovar diacetylactis.
Where flavour and aroma compounds such as diacetyl
are desired the lactic acid starter will include
heterofermentative organisms such as:
› Leuconostoc citrovorum or
› Leuconostoc dextranicum.
The primary function of lactic starters is the
production of lactic acid from sugars
Other functions of starter cultures may include the
flavour, aroma, and alcohol production
proteolytic and lipolytic activities
inhibition of undesirable organisms
Convert most of the sugars to lactic
Increase the lactic acid
concentration to 0.8 to 1.2 %
Drop the pH to between 4.3 to 4.5
A single bacterial colony
Food scientists frequently use the ability of
bacterial cells to grow and form colonies on
solid media to:
› isolate bacteria from foods,
› to determine what types and
› how many bacteria are present.
Bacteria are “streaked”over the surface of an
agar plate so as to obtain single colonies.
Obtaining single colonies is important as it enables;
› the size,
› shape and
› colour of the individual colonies to be
› It can also highlight the presence of
When conditions are right bacteria can double in number every
Can provide information on the size
and shape of the bacteria
› Rods (1)
› Cocci (2)
› Spiral (3)
It cannot provide enough information
to enable bacteria to be identified