Egg processing.pptx

presentation deals with structure of egg and processing of poultry eggs

1. Processing of eggs Dr. Vineetha P G

2. Egg

3. Egg is a complete food consumed throughout the world. Egg protein contains all the essential amino acid and has got highest biological value. Thus egg proteins are considered by the WHO to be the reference protein, to which all other proteins are compared. An average weight of hen egg is about 2 ounce i.e. 57g Structure and Composition of the Egg Whole Egg can be divided into three major components 1. Shell              2. Egg white    3. Egg yolk     

4. Factors affecting quality of egg 1.      Age of the egg 2.      Storage atmosphere 3.      Temperature of storage 4.      Relative humidity 5.      Pre-treatments given before storage

5. Testing the quality of egg Water test : this test is based on the principle of density. Eggs are simply dropped into water. Good quality eggs sink to bottom and poor quality ones float. Loss in weight is due to dehydration and thus increased air cell size.   Sensory test : Cracked, smelly, rough surface indicates poor quality Candling test : The egg shell is porous and allows the light to pass through. The eggs to be tested are placed in front of sharp, bright light and assessed for following factors a.       Cracks on the shell b.      Air cell size and position c.       Albumin and yolk position and firmness d.      Presence of any blood spot/meat spot  or foreign elements in the egg

6. Nutritional qualities of egg

7. Egg products are processed and convenience forms of eggs for commercial, foodservice and home use. Egg products are preferred to shell eggs by commercial bakers, food manufacturers and the foodservice industry because of convenience, labor savings, minimal storage requirements, ease of portion control, and product quality, stability and uniformity. PROCESSING OF EGG  

8. Classification of Egg Products 1. Refrigerated liquid products Egg whites, Egg yolk, various blends of Yolk and white 2. Frozen products Egg white, Egg yolk, Salted yolks, Sugared yolks, Whole eggs, Salted whole egg 3. Dried/Dehydrated products Spray dried egg white solids, Instant egg white solids, whole egg or yolk solids 4. Specialty products Freeze dried scrambled eggs, Frozen precooked products like Egg patties, Fried eggs, crepes, Egg pizza etc.

9. Production of frozen egg       Eggs are frozen to preserve them for use in food manufacturing. Before freezing, egg contents are separated from the shell and which may be frozen as whole egg, Egg yolk, Egg white or various mixtures of yolk and white. Freezing plants are generally combined with egg breaking facilities where eggs are received, washed and dried. Then the eggs are broken to remove the egg content this could be done by hand or with the help of machines. Freezing generally is done in a sharp freezer room with circulating air at -30 degree C. Freezing may take about 48-72h.

10. Egg white and whole egg can be frozen as such without any additives but it is difficult in case of egg yolk. While freezing egg yolk becomes gummy and thick due to gelation . This can be prevented by the addition of 10% sugar or salt or glycerin 5%. Sugar yolk will be used by bakers, confectioners and salted yolk may be used by mayonnaise manufacturers. These ingredients should be dissolved in the yolk during mixing and prior to screening.

11. Production of spray dried whole egg The whites, Yolks and whole eggs may be dried by several methods, like spray drying, tray drying, or freeze drying. Egg white contains traces of glucose and  galactose  which react with egg protein leading to  maillard  browning. This discolors the dried egg white. Browning can be prevented by removing glucose through fermentation by yeast or with commercial enzymes. This is known as  desugaring  and this is practiced prior to the drying of all egg white.

12. Functional Properties of Egg Content Eggs provide many desirable attributes as a food ingredient. The functional properties derived by egg contents are Coagulation, Emulsification and Foaming.

13. Coagulation The egg protein coagulates upon heating accompanied by binding of moisture and increase in viscosity. Heating causes denaturation of egg protein and gradually aggregates to form a three dimensional gel network. Thus eggs can be used as  thickening agent  in many food formulations mainly custards, cakes, pie fillings, cream puddings etc.  The coagulation temperature is influenced by pH, salts, other ingredients and duration of heating. Egg white coagulates at 62 – 65 degree C and egg yolk at 65-70 degree C. Heat coagulated protein helps to hold the shape of the product in which these are used. Thus eggs are used as binding agent in cutlets, chops etc.

14. Emulsification The phospholipids i.e. lecithin and certain proteins present in egg acts as an excellent emulsifying agent. In mayonnaise egg yolk acts as an emulsifier to keep oil suspended in vinegar. Foaming Eggs when beaten form elastic films, which can trap air. Egg and egg products are good foaming agents. Thus entrapped air expands during baking and gives fluffy and spongy product. Thus eggs are extensively used as leavening agent in baked products such as cakes and muffins.

15. Quality checks and storage of egg Good quality egg should possess following qualities once it is broken. 1.      Yolk is firm and stands up in the centre of white 2.      Egg white forms a definite ring around the yolk and thick white holds its shape 3.      No blood spots are present 4.      No bad odour Changes occur in egg during storage 1.      Increase in the size of air cell due to loss of moisture 2.      Increased pH due to escape of carbon dioxide. pH increases from 7.6 to 9.7 3.      Percentage of thin white increases, thus egg white loses its shape and runs easily. 4.      Water passes from white to yolk, thus fluid content of yolk increases.

16. Indicators to Determine quality of Eggs 1. White index:             White index = Height of thickest egg white portion/Egg diameter             Range: 0.08 - 0.1 2. Yolk Index             Yolk index = Height of Yolk/Yolk width             Range: 0.35 -0.45 3. Hough Unit (HU) Commonly used index to check the egg quality             HU = Height of thick white/weight of Egg For good quality egg HU is 72 and above and HU about 30 to 60 indicates poor quality. 4. Air cell size should be 2-3cm

17. Preservation of the Shell Eggs Wet immersion method Dry method

18. Wet methods Lime sealing method- Eggs are held in lime water for 14 -16hr, during immersion CO 2  released from the egg combined with lime to form calcium carbonate which deposits and seals shell pores. Then it is removed and stored at room temperature. Such eggs can be stored for 3 -4 weeks at room temperature. Water glass method 10% solution of sodium silicate is commonly called water glass. In this method Water should be boiled and cooled to 24 – 26 degree C, to remove the dissolved CO 2 , before the addition of calculated amount of sodium silicate. Eggs are kept overnight and then removed and stored at room temperature.

19. Dry methods Oiling In this method the quality of eggs is preserved by sealing the shell pores using suitable oil and thus preventing evaporation of water, CO 2  and other changes. Oiling can be done by Dip method or Spray method. Oiled eggs can be preserved upto 3 weeks at room temperature. Gaseous atmosphere Modified atmosphere packing of eggs proved to improve its shelf life. Maintenance of higher CO 2  pressure surrounding the eggs prevent CO 2  loss from the egg thus improves the egg quality. Thermization  or heat treatment methods Eggs are thermo- stabilized by immersing it in boiling water for 3 to 5 min while keeping the water stirred constantly. This heat treatment coagulates the albumin very close to the shell and thus prevents CO 2  loss.  Thermized  eggs can be stored at room temperature for 3-4 weeks. Cold storage or refrigeration : Eggs can be stored well for a long time up to 5 to 6 months at -1 c and 85-90% relative humidity.

20. Queries?