CHAPTER ONE

INTRODUCTION AND LITERATURE REVIEW

Yogurt
is a popular and healthy snacks and it has a lot of advantages over fresh milk
despite the fact that yogurt is also a bye product of milk. The advantages it
has over milk includes

(a)    It can’t get perish like milk which get
soured when it is not in refrigerator.

(b)    It is thicker than milk which makes it
easier to store and broadens it cooking.

(c)    It gives a lot tangy flavour that people
find appealing

(d)    It also contain low lactose unlike milk that
has high lactose which makes it to be easily digestible for some people that
has low lactose tolerance.

The bacterial that helps in converting milk into
this yogurt are

(a)    Bacterial which are of two strains

(1)
LACTOBACILLUS BULGARICUS

(2) STREPTOCCOCCUS THERMOPHILLIUS. Along with bacteria fungi also take part in the
formation of yogurt production. These micro organisms were mistakenly added to
milk along with a plant like bacteria LACTOBACILLIUS BULGARICUS which is
related to the strain of plant dwelling bacteria.

In
the process of adding more LACTOBACILLIUS BULGARICUS into the milk produce more
yogurt. it was now noted that STREPTOCOCCUS THERMOPHILLIUS  has same symbiotic relationship with
LACTOBACILLIUS BULGARIUM.

Yogurt
is form through the conversion of lactose to lactic acid by LACTOBACILLIUS
BULGARIUM so yogurt are made acidic through this process and also makes the
milk’s protein thicken and thereby making it viscous. The acidity also prevents
colonization from other microbes which aids in preservation.

By
breaking down lactose to make the lactic acid the microbes lower the levels of
lactose in the yogurt while the presence of STREPTOCOCCUS THERMOPHILLIUS helps
to fight along with LACTOBACILLIUS BULGARIUM against any microbes from outside
during the early stage of the process .

Originally
a simple fermented diary product, yogurt now has many variations and
personalities. It can be thin and runny or thick and firm. It can be made from
cow milk, goat milk, sheep milk, nut milk, soy milk, rice milk and from
numerous other creamy substances.

In
some countries the milk of buffalo, horse, yorks or camels is used for most of
this discussion, we refer to yogurt in its originally form for fermented dairy
milk. This was how yogurt was first developed, and most of the yogurt in the
world is made this way. Essential yogurt is the product of beneficial bacteria
fermenting milk and turning it into a thickened, acidic food that will stay
fresh longer than milk itself, and that contains millions of bacteria that are
welcomed by the human gut.

The
word yogurt comes from Turkish word meaning to curdle or to thicken. Its
probable that the earliest yogurt was made by accident in Mesopotamia around
5,000 BC, when milk producing animal were first domesticated. The milk was,
likely stored and transported in bags made from the stomach of these animals,
and the digestive juice and bacteria in the stomach livings made the milk
coagulated and become acidic. Not only was it a new and interesting food, but
the acidity helped to keep it edible for longer than if it had just sat out in
a bowl or jar, the acidity of the yogurt helps clean away dirty and rust and
also helps clear away dead skin and nourish healthy skin cells. Yogurt was a
popular food in the Middle East for thousands of years and has been a staple of
the eastern European diet. Its now eaten throughout the world, as a main
course, a snack, an ingredient in many recipes and a condiment. It has a gained
considerable popularity in America in the last forty or fifty years. Yogurt can
be mildly tart or quite sour, and can be thick enough to stand up on a plate,
or thin enough to pour or anywhere in between. It contain protein and calcium
as well as variety of vitamins. Additionally, the process of yogurt
fermentation is very similar to the process of digestion, so it can be easily
consumed.

Not
only does yogurt contain the same amount of protein and fat as the milk from
which it is made, it also contain calcium, riboflavin, vitamin B6, and
vitaminB12 while numerous claims have been made regarding the health benefits
and digestibility of yogurt.

Hahai
(2009)reported that a new type of yogurt prevent gastrointestinal distress; A
new yogurt, containing urea’s antibodies, as been shown to prevent helicobacter
pylori from binding to stomach walls and causing infection such as gastritis
and stomach ulcers. This yogurt is made using vaccine-making technology urea
injected into chickens allowed their immune system to produce an antibody to
increase called igy-urease. The antibody is then harvested from chickens eggs
and made into yogurt containing lactobacillus acidophilus, Bifid bacterium and
egg yolk igy-urease. This yogurt is particularly  significant in developing countries where standard
of care treatment like antacid and antibiotics are either unavailable or
unaffordable it is currently available in Japan, Korea, and Tawan, Fleet
G.,(1990).

The
aim and objectives of this project work, apart from the academic on our part by
the independent, is to make the public know different types of microorganism
that takes part in yogurt production, to put the mind of the public at rest
that not all microorganisms are harmful to human, to give the types, roles,
effect and importance of these micro-organisms that involve in the production
of yogurt and to produce good personelles.