PRESERVATION muslin cloth q The eggs are immersed

PRESERVATION         

q    Egg is a
perishable product having short shelf life.

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q   Preservation
of eggs should start from the point of production itself.

q   Collection
of eggs at least 3 times daily.

q   Using a
clean receptacle with ventilated sides and bottom, preferably filler flats.

q   Careful
handling of eggs during collection and while storing in filler flats etc.,

q Cooling the eggs quickly to 50oF or less
at 75-85% relative humidity.

q Marketing the eggs at least twice weekly.

 

FOLLOWING CHANGES OCCUR ON STORAGE :

      1.
Moisture loss through the pores

     2.
Gaseous (CO2) loss 

     3.
Change of PH

     4.
Movement of water from thick albumen to other        albumen layers and to yolk

     5.
Entry of microbes through the pores

     6.
Embryonic development

     7.
Absorption of foreign odours

THERE ARE TWO TYPE EGG PRESERVATION

A. Shell
eggs

B.  Liquid
eggs

                                   A.SHELL EGGS

PRINCIPLE

q       Retarding the microbial growth and
sealing the pores of the shell to minimize the evaporation of moisture and
escape of gases, thus reducing the physico-chemical changes in the egg.

q       Sometimes, a combination of methods is
employed for effective preservation.

METHODS:

            1.Immeresion in liquid

                 a) Lime water

                b) Water glass method

             2. Oil coating

             3.Gas

             4.Thermal processing

             5.Cold storage

            

1.IMMERESION
IN LIQUID

                         A) LIME WATER

1
litre of boiling water is added to 1 kg of quick lime.(caco3)

                              brought to room temperature

        
 4 to 5 litres of cold water        225 g of table-salt are added to it.

                                 

q
   To allow the solution to settled down and
filter with  muslin cloth

q     The eggs are immersed in this clear fluid
for 16 to 18 hours, and then taken out.

q     Eggs are dried at room temperature and
transferred to filter flats. The eggs can then be stored for 3 to 4 weeks at
room temperature

                 B) WATER
GLASS METHOD

q Water-glass
-10 % sodium silicate

q  The eggs are left immersed overnight in
water-glass.

q  It deposits a thin precipitate of silica on
the surface of egg shell, possesses intrinsic antiseptic properties and does
not impart odour or taste to the eggs.

 2. OIL 
COATING

q Oil
treating egg with a white, odourless, paraffin base mineral oil used.

q Sealing
the pores with oil .

q The
rate of CO2 escape is considerably reduced  and evaporation of water ,loss of egg weight
also reduced.

q  Oil treated eggs are kept in cold room.

q  If oil treatment is to be effective it should
be done preferably at the point of production the day after the egg is laid.

q These
eggs are not likely to absorb foreign odours.

q Specific
gravity – 0.855 to 0.870 at 15oC

q   Viscosity       –    
70 to 90 (should not be more than)

q   Cotton seed, linseed and groundnut oil are
good sealing agents but mineral oils are preferable since they are less subject
to oxidative changes during storage.

The commercial egg treatment oils are

q Heavy
paraffin oil (Central Food Technology Research Institute)

q  Myvacet 9-40 (developed at CFTRI – Mysore)

q  Myvacet 
5

q  Myvacet 
7

q  Petroleum jelly

q  Liquid paraffin

q  Paraffin wax

q  Coconut oil

q  Dalda

q  Carboxyl methyl cellulose

q  Technical white oil.

   
3.GAS

q   Intert gas usually N2:CO-94.6

q   The eggs are placed in a plastic bags or
special plastic cartons which are filled with this gas to seal the pores

q    But it is costly

q   Disadvantage is transpiration is
difficulty  and thus causes cloudiness of
albumin

  
4. THERMAL PROCESSING

q     This method is good for fertile eggs, since
it kills embryos and therefore is also known as ‘defertilization’ method.

q      This includes

                                                                                   
i.     
Flash heat treatment

                                                                               
ii.     
Thermostabilization

                                                                            
iii.     
Simultaneous
coating.

FLASH HEAT TREATMENT

q      The eggs are immersed for 2 to 3 seconds
in water at 71°C.                 

q      Advantage is that it destroys bacteria
present on the surface of shell besides coagulating a thin film of albumen
immediately beneath the shell membrane and thus seal the shell internally.

THERMOSTABILIZATION

q   The eggs are immersed in water at

             
49°C for 35 minutes or

             
54°C for 15 minutes or

             
56°C for 10 minutes or

             
60°C for 5 minutes in order to stabilize the thick albumen so that such
eggs retain fresh appearance much longer than unheated eggs

q Simultaneous oil coating and
thermo stabilization complement each other in
maintaining the internal quality of egg.

                                       5.COLD STORAGE

q       Eggs for cold storage must be clean,
unbroken, free from fungus and other infections.

q       A temperature of 0oC or 30-32oF
and relative humidity of 85-90% is recommended for cold storage of eggs to
preserve them for 5 to 8 months.

q       For short period of preservation of 2 to
3 months, eggs can be stored at 10-12oC or 50-55oF with a
relative humidity of 60-70%.

q        Intact eggs are held at the lowest
possible temperature that will avoid freezing and bursting of the shells. 

 FREEZING

q    Yolk and while contents  may be frozen separately

q    The egg content frozen at 10oF
to30oF or below zero

q    Stored for 12 months

q    Defrosting the frozen egg containers carried
out in egg room at the temperature of 12.8oC or cold running water

q    Defrosted eggs are used within few hours

q    Its quality determined by
odour,apperance,SPC,sediment and functional tests

q    Frozen eggs free from mouldy,sour  or putrid odour

q    It should have 25.5% of solid and SPC not
more than 20,000,000/ gram

     
                                   B.LIQUID
EGGS

DRIED EGGS

              
This is another method of preserving egg contents or edible eggs.  Egg products of commercial utility are
prepared by drying or freezing eggs. 
Albumin flakes, yolk and egg white powder can be produced by drying
process. 

FROZEN EGGS

                   Frozen yolk or frozen egg white
can be produced by freezing.

                Egg white powder production –
spray drying

                Albumin flakes – pan or cabinet
drying method is mostly adopted

 

q   Finally preservation of quality of egg or egg
contents to maintain its flavour.

q   Eggs are pick up flavour from the area.As
such storage area onion ,decaying veg material oil,gasoline or organic solvent
to be avoided.

REFERENCES

       Indian chicken.com