Preservationof shell eggsIn order to preserve eggs they has to beproduced of good quality. Therefore any method of preservation starts from thepoint of production itself. The following practices are recommended as routinefor the production of quality eggs on the farm. · Collection of eggs at least 3 times daily. · Using a clean receptacle with ventilatedsides and bottom, preferably filler flats.
· Careful handling of eggs during collectionand while keeping in filler flats etc. · Cooling the eggs quickly to 50oFor less at 75-85% relative humidity. · Marketing the eggs at least twice weekly. There are several methods of egg preservation of whichsome are explained belowa. Drypacking Eggs are kept in an earthen pot with cleandry packing material and the pot is buried in wet sand.
b.Immersion in liquids This is one of old method and it primarilyprevents the evaporation of moisture from the egg. Depending on the liquid usedit may also inhibit bacterial decomposition by chemicals action or by physicalmeans such as occlusion of air passages/pores. 1. Limewater treatment Lime water is prepared by mixing about 0.5kgof quick lime (calcium oxide) in about 1 litre of boiling water. After settlingthe mixture clean supernatant liquid is poured out into a jar to which sodiumchloride of 112 grams/litre may also be added to increase the specific gravityof water and will minimize the chance of breakage of eggs.
In this solution,2.5 liters of cold water is added and filtered through muslin cloth. Keep theeggs in a glass jar or earthen pot and pour the lime solution over the eggs toimmerse. Keep the eggs in solution for 24 hours. After 24 hours taken out theeggs, dry and arrange in filler flats. Eggs can be persevered for 2-3 months ina good edible condition at normal ambient temperature. 2. Waterglass method A 10% solution of sodium silicate is preparedin hot water and allowed to cool.
The cooled solution is poured into a jarcontaining the eggs till they are immersed completely. The jar is covered andkept in a cool place where the temperature should not exceed above 700F.Eggs preserved by this method are usually punctured before boiling to avoid thebreakage of shell while boiling and it also helps for easy peeling ofshell. c.Shell – Sealing treatments 1. Coating with oil Or WaxThe rate of CO2 escape isconsiderably reduced. This is a fairly successful method of rendering the eggless permeable. It can be done by simply dipping the egg in a bowl oftasteless, odorless, colourless edible oil, having a specific gravity of about0.
855 to 0.870 at 150C; viscosity should not be more than 70 to 90and having a high boiling point so that at lower temperature it remains in theliquid form. If oil treatment is to be effective it should be done preferablyat the point of production the day after the egg is laid. Oiling is not asubstitute for refrigeration. These eggs must be held at a low temperature.Cotton seed, linseed and groundnut oil are good sealing agents but mineral oilsare preferable since they are less subject to oxidative changes during storage.Oil immersed eggs and these eggs are not likely to absorb foreign odours. Theoil treatment can also be done by spraying using a hand or electric sprayer.
The commercial egg treatment with oils are Heavy paraffin oil (Central Food Technology Research Institute Myvacet 9-40 (developed at CFTRI – Mysore) Myvacet 5 Myvacet 7 Petroleum jelly Liquid paraffin Paraffin wax Coconut oil Dalda Carboxyl methyl cellulose Technical white oil. d. Thermostabilization This method is good for fertile eggs since itkills the embryos and therefore is also known as ‘defertilization’ method. Itessentially consists of immersing shell eggs in hot water at 130oFfor 30 minutes which tend to coagulate the albumin and then the egg is cooledunder tap water. Treated eggs remain edible for 3 to 4 weeks even during summermonths. Though this method has many advantages such as stabilizing of thealbumin and sterilization of the egg shell, the egg looses the property offoaming to a remarkable extent. Moreover, embryonic development in fertile eggsis completely arrested. e.
Over-wrapping Over wrapping of eggs is commercially done byusing polyethylene, cellophane, polyvinylidene and other transparent, thin butsufficiently strong, films are used. These films should be impervious to gasesand moisture. Over wrapping of eggs in different atmosphere like carbondioxide, vacuum etc. have been tried. f.Cold storage This is the best and most efficient methodfor commercial storage.
Eggs for cold storage must be clean, unbroken, and freefrom fungus and other infections. A temperature of 0oC or 30-32oFand relative humidity of 85-90% is recommended for cold storage of eggs topreserve them for 5 to 8 months. For short period of preservation of 2 to 3months, eggs can be stored at 10-12oC or 50-55oF with arelative humidity of 60-70%. Intact eggs are held at the lowest possibletemperature that will avoid freezing and bursting of the shells. It has beenobserved that intact eggs do not freeze at temperature between -1.
5oCand -2oC and the relative humidity must not go beyond 90%. g.Dried and frozen eggs This is another method of preserving eggcontents or edible eggs. Egg products of commercial utility are prepared bydrying or freezing eggs. Albumin flakes, yolk and egg white powder can beproduced by drying process. Frozen yolk or frozen egg white can be produced byfreezing.
For egg white powder production the best known method is spray dryingand for albumin flakes, pan or cabinet drying method is mostly adopted. h. PlasticationIt’s a new method of preserving eggs at room temperature.Also called as the “plastification” in situ of the shell, using aliquid synthetic polyvinyl chloride acetate plastic. The plastified eggs can bestored at 220 C for periods longer than 135 days.