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Cheese -
Cheese is basically a means of storing milk and has been used for this purpose for at least 2000 years. Cheese is the product made by separating the casein of milk from the liquid or whey.
The butterfat often accompanies the casein, but most of the lactose and other soluble milk constituents remain in the whey.
The
manufacture
of
all
cheeses
depends
upon
the
activities
of
selected
microorganisms.
Hundreds
of
different
kinds
and
varieties
of
cheeses
are
produced
by
introducing
many
variables
into
the
manufacturing
process.
However,
there
are
about
eighteen
major
types,
the
rest
being
variation
of
these.
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Cheese may be classified in several manners: on the basis of hardness, as nard, semi hard, soft cheeses; on the basis of the principal ripening agents, as mould or bacterial cheeses; on the basis of the method of coagulation, as rennet or acid curd cheese etc.
Cheeses
classified
according
to
their
consistency
and
the
use
and
nature
of
microbial
ripening
agents.
Several kinds of cheese in small quantities arc made in India. Panir is an ancient indigenous product. Other cheeses are similar to common western types. Soft cheeses include Surti, Bandal and Dacc a. Hard cheeses are the cheddar types.
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Most cheese is made from either whole or skimmed milk. Some varieties are prepared from cream and whey.
Milk from cows, goats, ewes mares and other animals has been used for the making of cheeses. Four steps are generally followed in the preparation of cheese.
These
are
(I)
inoculation
of
milk
with
starter
culture
and
curdling
the
milk,
(2)
processing
of
curd,
(3)
salting,
and
(4)
ripening.
Milk
inoculated
with
starter
culture
ferments
lactose
with
acid
production.
The
acid
reacts
with
calcium
to
give
calcium
lactate.
When
the
content
is
reduced
to
a
certain
low
point,
the
casein
precipitates
with
the
formation
of
firm
curd.
Starter
culture
consists
of
Streptococcal
lactis
or
S.
cremoris
if
milk
is
held
below
38°C.
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A starter culture for use at higher temperature (about 50°C) consists of S. thermophiles combined with species of lactobacilli e.g., Lactobacillus lactis, L.Curd may also be prepared by adding the enzyme renin to milk.
The watery fluid which separates out during the formation of curd is called Whey. It consists of 93 percent water, 5 percent lactose, and smaller amounts of minerals, vitamins, lactalbumin, and fats.
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The curd is separated from whey by various methods depending on the amount of moisture desired by various types of cheeses.
Draining of whey without pressure results in the production of soft cheeses, which have high moisture content.
Hard cheeses require curd of allow moisture content. This is achieved by heat, pressure, and cutting of the curd.
After the moisture content has been reduced to the desired limit, the curd is molded into a characteristic shape and size.
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Salt: (sodium chloride) is applied to practically all varieties of cheese. It is added by (1) floating the cheese in a strong brine solution, or (2) rubbing the surface of the pressed cheese with dry salt.
The flavour of Taw cheese curd is very bland, and the cheese is rubbery in consistency. To be made satisfactory for consumption, it must be set aside to ripen.
During ripening, the flavour, aroma, composition,
and
physical
properties
of
the
cheese
undergo
change
due
to
the
action
of
microorganisms
and
their
enzymes.
The
natures
of
the
changes
depend
on
the
microorganisms
present
or
added
and
the
control
of
temperature
and
relative
humidity
in
the
curing
rooms,
chambers
or
caves.
The
development
of
microbial
flora
for
ripening
varies
with
the
type
of
cheese.
In
Roquefort
and
blue
cheese,
the
curd
is
inoculated
with
spores
of
Penicillium
roqueforti,
In
Swiss
cheese
lactobacilli.
Streptococci
and
propionibacteria
arc
added
to
the
milk
before
the
curdling
process.
In.
Limburger
cheese
the
surface
of
the
curd
is
allowed
to
be
contaminated
with
desirable
organisms,
mainly
Brevibacterium
linens,
when
placed
in
the
ripening
room.
During
the
ripening
process,
the
degradation
of
lactose,
protein,
and
fat
is
brought
about
by
the
activity
of
a
mixed
population
of
microorganisms.
Lactose is degraded to lactic acid and smaller amounts of volatile acids, alcohol, and natural products. Bacteria of the lactic acid type are mall1ly responsible for the flavour of hard cheeses. Propionibacteria ferments lactose, producing carbon dioxide.
This results in the formation of holes or "eyes" in Swiss cheese. Degradation of protein and fat is considerably less in hard cheeses. In soft cheeses, protein is completely degraded to peptides and amino acids.
Cheese made from whole milk has considerable fat in the curd. Lipases elaborated by the mould hydrolyse the fat, releasing butyric, caproic, caprylic, capric higher fatty acids. Some of these acids are oxidized forming compounds contributing to flavour.
Many
undesirable
microorganisms
are
responsible
for
the
spoilage
of
cheese.
These
may
affect
the
flavour,
aroma
and
texture
of
cheese.
Coliform
species
and
certain
yeasts
ferment
lactose
with
the
production
of
acid
and
gas.
Gas
holes
are
produced
which
give
a
swollen
appearance
to
cheese.
E.
coli
also
imparts
a
bitter
flavour
to
cheese.
The
putrefactive
organisms
grow
and
become
active
when
the
acidity
of
cheese
is
reduced
during
the
ripening
period.
These
organisms
are
responsible
for
putrid
odours
and
flavours.
The
discoloration
of
cheese
is
brought
about
by
several
pigment
producing
organisms.
This may also be caused by chemical reactions with metals such as copper and iron from the utensils. Several epidemics have been traced to the consumption of cheese contaminated with pathogenic organisms.
The
organisms
most
commonly
associated
with
cheese
born
infections
are
Staphylococcus
aureus,
Clostridium
butylicum.
Brucella
melitensis
and
several
species
of
salmonella.
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