L5 : Test for Protein in Food - Components of Food , Science, Class 6 Video Lecture

hello friends this video on components
of food part 5 is brought to you by
example or calm no more clear from exam
now in a similar way we can also try to
test if a food item contains protein or
not so let's say a bowel of pulses is
kept in front of you and you are asked
to whether it contains proteins but now
you have an idea right that I should be
able to test that the way I tested it
for carbohydrates there should be some
other way for proteins as well yes there
is so before we talk about the test for
proteins let's see what are proteins so
these are compounds which are essential
part of living organisms so living
organisms very very bad we need proteins
in fact our body the structure of our
body is also made up of protein so when
you look at the entire body structure of
human beings not only human beings if
you talk about different organisms as
well so you see that proteins they form
a very major part of our bodies so if
they not only help in growth development
and tissue repair of our body they also
form a part of the structure of our body
so if you look at it inside our body we
have enzymes we have hormones and all of
these play a very critical role
what are hormones they are nothing but
proteins what are enzymes they are again
nothing but proteins so the various
chemicals which are you know getting
secreted inside our body and they are
playing an important role inside our
body they are nothing but proteins so
proteins are an essential part of living
organism so we cannot think of any life
form without proteins now some of the
food items which contain proteins add
milk cheese fish ground nuts needs
pulses so these are very rich source of
protein so that is why I said that
people who are non-vegetarian they
already have a lot of proteins in their
diet with with through fish and meat but
those who are vegetarian that is they do
not eat a food or indirectly from other
animals so they should concentrate a lot
on foods which are rich in
for example ground birds if for example
pulses so pulses should definitely be a
part of your diet because they are very
rich source of proteins now again the
same question how exactly do we test
whether a particular food item contains
proteins or not so let's look at the
tests for proteins so for this what we
need is a caustic soda solution
so what else caustic soda so caustic
soda is actually sodium hydroxide which
is written as n a o H or you can say
this is sodium hydroxide so that is
caustic soda now again how do we prepare
caustic soda solutions available
whenever we have to prepare solution of
anything what we do is we just mix that
substance with water and that's how we
are able to prepare solutions like we
prepared iodine solution we added a few
drops of iodine to water and we got
iodine solutions similarly here also
what we will do is we will take some
sodium hydroxide so look at sodium
hydroxide this is how it looks like it
is in the solid form it is white in
color and it is available in the form of
slates or granules and here in this
picture you see granules but it is also
available in the form of flakes and this
sodium hydroxide is used in paper
industries and textile industries a lot
it is also used in soaps and detergents
and they are also very good drain
cleaners so those are some of them
places red sodium hydroxide or caustic
soda is being used now let's see how
would we make use of caustic soda
solution so what we will do is we will
take around 10 grams of caustic soda
because caustic soda is available in
solid form as I said so we will take
around 10 grams of caustic soda and we
will add in 200 ml of water and when we
mix them properly what we get is
positive soda solution so this caustic
soda solution will be used to test for
proteins
so this is one thing that we need to
test proteins now there could be another
solution that we can use which is copper
sulfate solution what is copper sulfate
it is cuso4 so that's copper sulfate so
this copper sulfate solution can also
help us to test the presence of protein
so copper sulfate is actually an
inorganic salt that is a salt which
doesn't contain carbon so that's why it
isn't so you can say it is an in organic
salt so look at it it is like in the
form of crystals so it seems to be
powdery but actually when you look at
copper central solution it is like a
powdered form of copper sulphate
crystals so they it is formed when
copper metal is treated with
concentrated sulfuric acid so copper is
a metal right so when copper metal is
reacted with concentrated sulfuric acid
so then you get copper sulfate so that
is how you get copper sulfate its color
rinsed is bright blue in color it is in
crystalline form so if you look at it
more closely you will see that it is
like tiny crystals of copper sulphate
and it is highly soluble in water so it
is water soluble so it will be easier to
make a solution of copper centered so
when you mix it with water it will get
dissolve in water so how would you
prepare the solution you take
approximately 2 grams of copper sulfate
and you add it to hundred milliliter of
water so what you get is this copper
sulphate solution which is slightly blue
in color obviously because the crystals
are blue in color so when it dissolves
completely in water so the solution also
returns blue so now we are ready with
the caustic soda solution and the copper
sulfate solution so now we will see how
exactly do we test a sample with protein
for protein let's look at a procedure so
let us think of a substance which is
rich in proteins here I have considered
the example of
one says no pulses are very rich source
of protein so we know that they can
interview but here we will just try to
perform this test using the caustic soda
solution and copper sulphate solution to
see that how it proves that it contains
proteins so so for doing this test the
first thing that we have to do is we
need to make a paste of this pulse s
because the pulses are like in the form
of granules so you actually need to make
a paste of it maybe in the mixer grinder
once you make a paste of it then take
the paste in a test tube so this is your
test tube and inside the test you you
take the paste which you have prepared
by grinding these pulses now here you
would have the paste of the pulses and
you also add some water to it so you
will get a kind of a liquidy a
semi-liquid thing which has the paste of
the pulses and some water okay so now
what we do now we add to it some two
drops of coppers and fit solution so
around approximately two drops of copper
sulphate solution is being added to this
test tube and then around 10 drops of
caustic soda solution is added so you
first added two drops of copper sulphate
solution then you added around ten drops
of sodium hydroxide or caustic soda
solution and then you shake it really
well test you so that all the things get
mixed together very well the caustic
soda solution copper sulfate solution
the paste of the pulses everything
should get mixed really well now once
you have shaken it really well after
that you leave it undisturbed for a
couple of minutes you just leave it as
it is do not move wait do not shake it
so leave it for some time and then what
do you observe you observe a change in
color as you can see here so what
happens is a violet color appears and
this appearance of violet color
indicates the presence of proteins are
they're the violet color doesn't appears
that means protein is not present in the
sample but in this case pulses are very
good source of proteins so obviously
violet color clear so this is how you
can test you not only with the pulses
you considered any idea maybe you can
take some potato smash them put them in
a test tube add some water and then you
add two drops of copper sulfate add ten
drops of sodium hydroxide and just try
to see if the color changes or not so
that if the color changes that means
that if the color changes to violet that
would mean that if proteins are present
in potato if it doesn't that would mean
there is no protein present in potato so
this is how we can check which food
items contain proteins and which do not
so here we would say in this scenario
that the protein test for the pulses is
positive now similarly you can try out
the protein test for various substances
and for all of these substances it turns
out to be positive whether you talk
about rounders you talk about Fisher's
we talk about yogurts you talk about
pulses for all of them the protein test
is positive thank you please visit
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