Food preservation : Heat & Cold treatment - Micro Organisms, Science, Class 8 Video Lecture

hello friends this video on
microorganisms friend and foe part 23 is
brought to you by exam feel calm no more
fear from exam and then the final method
is the heat and cold treatment so let us
first look at the heat treatment now you
would have often seen at your home that
whenever you I mean whenever you
purchase milk what happens your mother
for storage boils milk and then keep it
aside by
because boiling milk helps to keep it
good for a longer period of time
now what happens during boiling so
whenever you heat a food item it
destroys the microorganisms which can
spoil the food in fact because of this
this reason only like when we buy raw
vegtables offer it at sale they do not
eat the raw vegetables without washing
so when washing some of the
microorganisms are like removed by water
now when you boil it the remaining
microorganisms also get killed so that
is boiling helps to destroy the
microorganisms and thus you get a more
fresh food so one example of heat
treatment is sterilization you would
have often seen that for children who
feed on boxes their bottles are
sterilized very often almost on daily
basis their bottles are sterilized so
water is what sterilization it is a
process in which a food is heated to a
very high temperature temperature
greater than 100 degree Celsius for a
sufficient time because when you we talk
about heat treatment it also plays a
very important role that for how much
duration you are heating that food
object so the greater the duration of
heating the better will be dead so
therefore when we talk about heat
treatment now what in order to destroy
different types of microorganisms we
might need to heat it to different
temperatures
that's because different microorganisms
have different thermal resistances so
maybe for one microorganism you might
need to heat it to a higher temperature
when compared to some other
microorganism
so but overall this heat
quint will fully or partially destroy
the microorganisms that are capable of
spoiling the food so it is a good
conservation technique for long
durations you can preserve it for quite
a long time now in sterilization what
happens is the temperature is also quite
high and the duration for which it is
done that is also quite high so when it
is heated to to a very high temperature
for a very long time then most of the
microbes get destroyed
so for perfect sterilization the
container as well as the content both
are sterilized now when you talk about
the tailor sterilization I gave you the
example of the feeding bottles of small
babies you would have seen that their
bottles get sterilized almost every day
so how is it sterilized because for
babies their body is quite weak and they
might get that infection even quick more
quickly than adults so they are bottles
they are boiled in water to have a high
temperature and for quite sufficient
time in fact you have bottle sterilizers
available in the market these days so
that means the container gets sterilized
so that there is there are no
microorganisms present in the container
so that's how you are we are keeping the
container safe and the content is also
sterilized by in this case the container
is milk so obviously we boil the milk
sufficiently so that it is microbe free
so not only for these feeding bottles
but in hospitals most of the equipments
like the syringes or the knives or the
scissors whichever is used in hospitals
they are all sterilized so all the
surgical equipments they are sterilized
before they are being used now in order
to ensure even better cleanliness or
better hygiene the container is
sterilized the content is
and then they both are packaged in an
environment which prevents the growth of
microbes so that nowhere there is a
scope where microbes can attack now in a
very similar way we can also preserve by
old treatments like how we saw that by
boiling we can destroy a lot of
microorganisms in a very similar way if
we reduce the temperature in that case
also low temperature is not favorable
for the growth of several microbes so
low temperature prevents the growth of
microorganisms and this is known as the
cold treatment and your neck
degeneration is the best example of cold
treatment so when you keep the loaf of
bread inside the refrigerator it remains
perfectly fine for quite a few days at
least for 3-4 days it is fine it it does
not get infected by East but if you
leave it outside you see this kind of a
white layer forms on it and that happens
due to the from them so low temperature
will also inhibit the growth of several
microorganisms and that's why we use
refrigerator basically so that we can
store things for longer duration so now
based on this heat treatment and cold
treatment let us talk about something an
important concept for pasteurization
so what has passed in isolation so here
we will see that it is a combination of
heat treatment and cold treatment and it
is extremely useful for storage of dairy
products it helps to preserve milk and
all the dairy products for a long time
so you would have seen that these days
you get milk in packets which can be
stored for a couple of days similarly
you get certain will certain packet
milks which remain good even for a
couple of months and in some the
pasteurized milk are not even needed to
be boiled
because oh because since they are my
group free so you don't really need to
boil it so what does pasteurization so
it is a process in which milk is heated
to about 70 degree Celsius for 15 to
thirty seconds so for small time small
amount of time it is heated and then
suddenly it is chill and stored so first
you heat it a little bit so when you
heat it that heat treatment it tends to
kill a couple of organisms and then
immediately you chill it you put it
inside a refrigerator kind of place and
then after that it gets rid of all the
microorganisms so why do we do both
heating and cooling as a part of
pasteurization
so in pasteurization what we want to do
is we want to reduce the number of
pathogens we want to reduce the number
of disease-causing microorganisms so if
you compare pasteurization with
sterilization in sterilization our aim
was to kill all microorganisms present
in the food it doesn't matter whether
they are capable of causing a disease or
not we just want to kill all the
microorganisms so for that purpose we
just heated it to a very high
temperature but here in this case we do
not want to kill all the microorganisms
we only want to kill those which are
pathogens that is which can cause
diseases in fact we want to reduce their
number of pathogens so we do not want to
kill them completely we just want to
reduce their number to a safer enemy
limit therefore what happens is in
sterilization if you sterilize a food
item in that case the taste of the food
product gets impacted because you heat
it to a very high temperature so
therefore the composition of the product
changes but in pasteurization the taste
of the food product doesn't change
because you just heat it to a minimum
temperature and then you suddenly chill
it so that means pasteurization aims to
reduce the number of pathogens so here
what happens is the pathogens are killed
and also the number of microbes are
aimed to be reduced so this process of
pasteurization was discovered or
invented for the first time my home is
pasture in 1864 so what he discovered
was he discovered this concept with a
beer and wine so when he heated beer and
wine he found that heating them was
enough
most of the bacteria that caused the
spoilage of beer and wine so that's how
this idea stuck him that okay so if we
provide some heat treatment followed by
cold treatment we can actually store it
for a longer period of time and that is
why it was named as pasteurization after
his name so let us look at the
advantages of pasteurization first of
all it destroy the pathogens in milk so
all the disease-causing organisms get
killed because the high temperatures
short time pasteurized milk so it raise
it to a high temperature but at the same
time it is done for a very short time so
that means it is able to destroy the
pathogens it also reduced the number of
spoilage microbes so firstly the
disease-causing microbes gets killed
other microbes which are capable of
spoiling the food they also be reduced
and thirdly the shelf life of wealth
against increase that means the milk can
be stored for a longer period of time
now for some milk which are heated to a
high temperature for a short time so
there are different ways how you can
increase the shelf life so if you heat
the milk to a high temperature but for a
short time so maybe for a few seconds
but to an extremely high temperature so
in that case god shelf life may be from
two to three weeks now if you heat the
milk for a higher temperature for a
higher time so that is called ultra
pasteurized so ultra pasteurized milk
can stay good for two to three months
now if I'm trans pasteurized milk is
followed by sterile touching wet when I
say sterile packaging that means the
container where the milk will store that
has a state that is sterilized the
container is sterilized and when the
container and the contents have been
together that time also the environment
is made microfleece so that is one
sterile packaging so if I'll try
pasteurized milk is followed by sterile
packaging so in that case it can last
for almost nine months so therefore you
would have seen that there are different
types of milk which are available in the
market these days so some milk it is a
really good for a very long period of
time so this is how a pasteurization wok
works and result some of the techniques
which helps us to preserve food items
for a longer period of time thank you
please visit www.payoor.com to watch
more educational videos with a better
experience please do not forget to Like
and subscribe to our YouTube channel for
latest updates thank you once again