from thrillers by Julion Okram


The most commonly used eggs in cooking are hen's eggs (domestic chicken, Gallus gallus f. domestica).  Far more rarely utilised are quail, duck, goose, or other eggs.  All parts of the egg are edible, although an unsoftened shell is mechanically problematic:  Ingested sharp fragments can cause health problems in some cases.  Various types of microbial contamination are relatively common and pose the highest risk.  There are two typical scenarios with compromised eggs:.  1. The imperceivable form, in which no apparent changes are observed on the egg; still, an infectious disease is contracted after eating it.  2. The noticeable form manifests through changes in appearance and/or odour (egg rot).  In this second form, we may be at risk of infection and poisoning from the accumulated putrefactive products.  Both of these contamination threats are our most significant concern when using eggs.  In addition, from a nutritional point of view, we also avoid old eggs.  While these do not pose an infectious or toxic threat, the nutrients damaged by oxidation and rancidity do not benefit our long-term health.

Egg Anatomy

Fig∙ 1.  Poured-out hen's egg.  A healthy egg contains a clear white.  The yolk should be spherical, unbroken, and evenly coloured - pale to deep yellow, sometimes even orange (depending on the breed of hen and her pasture or feed).  Numerous small blood spots of a distinctive red colour are sporadically seen at the interface between the white and the yolk.  They are not a quality defect, but if they annoy or disgust us, we can pick them up or drive them away with a fork or knife.  The two twisted, semi-transparent cords (in this case, one at the top of the yolk and the other to the left of its left edge) are part of the regular egg-white's structures of each egg (see text).

Main Parts of Raw Bird Egg

The egg is a reproductive organ of birds.  It is laid by females.  If the parent birds sit on the fertilized egg (or if it is kept warm by artificial means, such as in an incubator or hatchery), a baby bird will hatch from it.  Chilled eggs do not develop.  Therefore, deliberate cooling as soon as possible after laying is used for food production.

1.  The shell is a calcium-hardened envelope.  In hens, it is either completely uncoloured (white) or, not infrequently, light brown (occasionally slightly marbled).  The shell gives the egg its typical rounded shape, spheroidal to somewhat elongated, typically with one end more rounded than the other pole (obtuse / round / large and sharp / pointed end of the egg).

2.  Egg white adheres to the shell on the inside.  It is covered by a whitish membrane of a parchment-like appearance.  This is attached over the entire shell's surface, except for the blunt end, from which it is considerably distant.  Thus, creating a conspicuous air chamber.  Its location is predominantly associated with the large end, but there is a vast anatomical variation.  The air sac's anomalous location does not affect egg edibility.  The inner part of the white is more rigid and mucousy, semi-tightly surrounds the yolk, and even after the egg has been broken, it remains close to the yolk.  The peripheral part of the egg white under the shell tends to be more watery and may spill freely.  Both white components are translucent and non-murky.  The exception is the two denser cord-like tufts connecting the yolk membrane to the white (called chalazae).

3.  The yolk floats in the middle of the white mass as a soft yellow ball.  Exceptionally, it may move laterally below the shell's surface.  From time to time, we also come across a double-yolked or triple-yolked egg.  There is no need to worry about this natural variability - multi-yolk eggs are just as tasty and nutritious as single-yolk eggs.  Nor do they have miraculous healing powers, as is sometimes said.  They are simply rarer counterparts of ordinary eggs.  The yolk contains denser and thinner areas of fluctuating colour saturation, but explaining that would exceed the point of culinarily important detail.

Which Egg Parts are Good for What

Cooking & Baking

Whole eggs in shells

Intact eggs are either soft-boiled (usually 2 to 3 minutes, depending on their size and atmospheric pressure, whose fluctuations alter the boiling point of water) or hard-boiled (approximately 10 to 15 minutes).  The soft-boiled eggs are eaten with a teaspoon directly from the shell through a hole.  The hard-boiled eggs need peeling.  Apart from the Czechoslovakian fairy tale "Byl jednou jeden král" [EN: There Was Once a King, 1954], there are no known recipes for throwing shelly eggs into the dough to prepare human food.

Whole shell-free eggs

Typical egg-only meals are scrambled eggs, omelettes, and bull's eye.  Then there is a plethora of mixed dishes containing eggs - salads and spreads, cakes, pancakes, and main courses (custards, fritters, eggy mushrooms...).  Iconic and impossible-to-do-without-eggs specialities include, for example, the traditional semolina dumplings for the finest festive soups.


In the old days, eggshells were used to prevent or treat calcium depletion during wars, famines, pharmacy closures and other situations leading to nutritional deficiencies.  They were dissolved in vinegar, squeezed lemon, sauerkraut juice, etc.

Egg whites 

The egg white has a different chemical composition than the yolk.  We separate it whenever we need to take advantage of its specific cooking or mechanical properties.  A unique example is whipped egg white snow, which cannot be made from egg yolk or other foodstuffs.  This stiff froth can also be eaten uncooked (e.g. its sugary mutation stuffed into pastry tubes).  Among its many uses are stirring-in into lightened doughs, fluffy pie fillings (nutty, poppy seed...), a delicious foamy topping for rice pudding, Brown Betty and the likes, meringues, or the children's favourite airy puffs in classic Oeufs à la Neige.


A unique egg yolk creation that cannot be made from egg whites or other edibles is mayonnaise (flavoured egg yolk-and-oil emulsion).  The use for the preparation of yolky liqueurs is also inimitable.  Some doughs and batters are most successful when separated egg yolks are used instead of whole eggs.

Other Uses


Eggs or their components are sometimes used to manufacture home-made and industrial face masks and shampoos.


Perhaps everyone is familiar with the traditional Easter embellishment - painted eggs (Easter eggs).

DIY glueing

Dried and hardened egg speckles can be tedious to remove from clothes or tiles.  It§s therefore not surprising that whipped eggs or mixtures with fresh curd and other sticky admixtures were said to have been used to mend broken porcelain.

Building construction

The centuries-old rumours seem to have been confirmed.  Analysis of the masonry of historic buildings is said to have shown that ancient builders did indeed mix eggs into a mortar and other building materials.  Today, relevant research is underway with the twin goals of improving modern concretes' structural and dynamic properties while reducing carbon dioxide emissions.  References:  Experimental study of natural concrete additivesExperiments on the enhancement of cements with ground eggshells.

How to Select and Assess Eggs


First, we must decide whether we are looking for non-avian soft-shell eggs or classical hard-shell bird eggs.  

Soft-shelled eggs

Simple ova or oocytes are microscopic to millimetre-sized cells.  A common characteristic of such eggs is a softish, membranaceous or leathery envelope.  A hard-style cover is rare in these eggs.  Soft-covered eggs are laid, for example, by insects, amphibians or fish.  Another example is mammalian ovulation - the release of sex cells from the female and women's ovaries.  Some types of soft eggs are eaten - roe, caviar.  We will discuss this egg category in another chapter.

Common-usage hard-shelled eggs

The most known eggs are large bodies, typically hard-shelled, laid by birds, oviparous mammals, or sizeable reptiles.  Tiny eggs of small birds are sometimes referred to as eggies because of their small size and dimensional similarity to the soft-skinned eggs in the paragraph above.

Hen egg sizes

A gram here, an ounce there - such divagations are usually lost in cooking and are not noticeable in the resulting cookout.  However, it's not always overlookable whether we take ten S eggs or ten XL eggs.  The difference in the cumulative volume may be bigger than twofold, which can already cause a severe change in the consistency or flavour of the food prepared.  Therefore, straightforward, helpful and concise systems of labelling chicken eggs are in force in many countries or internationally.

Egg sizing example 1:   European Union (EU) 
Effective since:  1 July 2008 
Source:  Regulation (EC) No 589/2008 

                 grams         ounces    

                 g / egg       oz / egg  


S   Small       ~30 - 52,99    1 - 1.9   

M   Medium       53 - 62,99    1.9 - 2.2 

L   Large        63 - 72       2.2 - 2.5 

XL  Extra Large  over 72       over  2.5 

Egg sizing example 2:   United States of America (USA) 
Source:  USDA - United States Department of Agriculture 

This system is based on weight per dozen (twelve) eggs, with no guaranty whatsoever about individual eggs in the box.

             ounces                     grams 

             oz / dozen   oz / egg      g / egg       


Peewee       15 - 17.99   1.25 - 1.49   35.44 - 42.51 

Small        18 - 20.99   1.50 - 1.74   42.52 - 49.60

Medium       21 - 23.99   1.75 - 1.99   49.61 - 56.69 

Large        24 - 26.99   2.00 - 2.24   56.70 - 63.78

Extra Large  27 - 29.99   2.25 - 2.49   63.79 - 70.86 

Jumbo        over  30     over  2.5     over  70.87 

Egg sizing example 3:   Canada (CAN) 
Source:  CFIA - Canadian Food Inspection Agency 

             grams        ounces

             g / egg      oz / egg    


Peewee      ~30 - 41.99   up to  1.47 

Small        42 - 48.99   1.48 - 1.72

Medium       49 - 55.99   1.73 - 1.97 

Large        56 - 62.99   1.98 - 2.21

Extra Large  63 - 69.99   2.22 - 2.46 

Jumbo        over  70     over  2.47

(The values in local national measurement units were reciprocally recalculated to enable international comparisons.)

Fig∙ 2.  Hen eggs are vastly variable in size.  Worse, labelling in shops may not be reliable.  In some countries, few would dare label an egg the size of a garlic clove with the pompous "EXTRA LARGE" - while elsewhere, offering such miniature eggs in a metropolitan supermarket may be commonplace without the slightest embarrassment.  No wonder our cooking recipes don't work out...  To ensure our cooking doesn't fail, we should measure the egg quantities by volume (for example, in millilitres in a small measuring cup) or weigh them.  After writing down the optimum dose, in the future, a given culinary feat will not fail because of a disproportionate egg mass.  In J· Okram's recipes, you can rely on the fact that if precision is required, the dosage of eggs will be expressed fittingly.  Whenever needed, the prescribed input will be given not only in pieces, but you will find the size specification (S, M, L, XL) and possibly also the weight or volume of the recipe-specified egg mass.

Origin of Eggs

Only those who have their own backyard with a chicken coop know what sort of life their hens have and what they eat.  Those with a microbiology laboratory at their disposal can also know better about the biosecurity of the eggs they eat.  Who among us enjoys such conveniences?  Probably no one.  Most people have to rely on supermarket chains.  Nevertheless, we are still left with some choices thanks to the mandatory uniform national egg-labelling systems in the civilised world.

Marking on the shell

Every legal egg in the retail consumer chain in most countries must be stamped with a code.  Its format varies slightly depending on the printing machine and place-specific regulations, but in principle, it must contain mandatory crucial information.  For example:

KK  DD 9-9


9   = farming method

KK   = country of origin (HU Hungary, PL Poland, ...)

DD   = county / district code

9-9   = plant / farm ID

Farming method

Those who care whether they put the results of animal suffering (and what kind of suffering) on their table, they check the coding of husbandry practices against the following key:

0  -  fully ecological and humane production

1  -  eggs from free range hens

2  -  eggs from barn hens

3  -  eggs from caged hens (enriched cages are the only acceptable modality in EU)

Fig∙ 3.  Eggs most definitely are of animal origin.  The source of eggs should be clearly indicated on each egg and packaging.  We usually cannot verify whether the information is accurate or not, except in funny cases when the nonsense is obvious.  We know for a fact that some schools of vegetarianism allow the consumption of eggs (it's mainly vegans who reject them).  However, acceptance by vegetarians does not automatically mean that eggs have ceased to be of animal origin.  As far as can be ascertained, non-animal eggs have never existed heretofore and are unlikely to arise any time soon.  The author of the depicted sign did not specify what his strong statement referred to.  It looks bizarre if the non-animality announcement shines the most garishly and prominently from the hen's eggs packaging...

Egg Freshness

Water test

The shell is not completely airtight.  It is permeable to both gases and water vapour.  This means that each egg slowly dries out from the moment it is laid.  The more water escapes, the airier and hence the lighter the egg.  Water evaporation will inevitably change the egg's buoyancy: the older it gets, the more it becomes buoyant.  A simple agedness test is carried out in cold water at least 10 centimetres deep.  As a rough guide, the following time dependence applies:

● freshly laid, one-day-old and two-day-old eggs - lying on the bottom flat in a horizontal position, i.e. with the long axis wholly or almost parallel to the bottom of the container

one-week-old egg - the blunt end begins to rise slightly

two-week-old egg - standing vertically with the broader ending upwards, but with the sharper pole still touching the bottom

three-week-old egg - hovering above the bottom

one-month-old and older egg - floats near the surface or partly above

Is the swimming test accurate?

No.  It is only roughishly indicative.  Each egg's porosity may differ; more porous eggs will dry out more rapidly and float earlier than more vapour-tight eggs.  The evaporation rate also depends on the shell's washedness / de-greasedness, storage temperature, air humidity, barometric pressure, etc·.

Is an egg lying "flatly" guaranteed to be fresh and safe?

It probably is alright, but there is no guarantee.  Even a horizontally resting egg can be contaminated with, for example, salmonella; it has nothing to do with the floating.  On the other hand, some eggs have an abnormally positioned (sideways) or tiny air bladder, so even after weeks, they can still remain in a horizontal position.

Is a floating "surfacing / poking out" egg definitely old or rotten?

No such 100% correlation exists.  Even a fresh and absolutely perfect egg can float on the surface.  This happens, for example, if it has an overdeveloped air chamber.  However, buoyantly uplifting eggs should be avoided if possible.  They may only be used after the shell breaking, followed by a thorough safety check.

Fig∙ 4.  Egg float test.  The fresher the egg, the more it sinks to the bottom.  The older it is, the more it rises or floats towards the surface (see details in the text). The role of the water test in non-expert home egg assessment is only as an aid and an indirect indication.  The correct kitchen procedure is as follows:

STEP 1: ● For every single egg, we want and need to know its origin (own breeding, shop, auntie across the creek...).  

STEP 2: ● For every single egg, we want and need to know its laying date.  

STEP 3: ● For every single egg, we want and need to know how it has been stored since laying. 

STEP 4: ● We will perform the swim test.  Immerse the eggs in cold water (0 °C to 25 °C  /  32 - 77 °F).  For each one, observe whether it sits on the bottom or floats.

STEP 5: ● Sort the eggs as follows:

GROUP A. ● Eggs proven to be within 2 weeks of laying, of hygienically and ecologically sound origin, with intact shell, adequately stored (i·e· if the temperature has never exceeded 4 °C (39 °F) for washed eggs / 18 °C (64 °F) for unwashed eggs), lying or standing on the bottom (they must be touching it):  ▶▶▶  USAGE 1  or  STEP 7 

USAGE 1: ● Only Group A eggs after step 5 are minimally risky and recommended for in-shell cooking (soft-boiling, hard-boiling).  After cooking, a final check should be made according to step 6:

STEP 6: ● Check for integrity, texture, colour and aroma after shell-on cooking.  Eggs that have oozed and coagulated in the water while boiling, unhealthily or overly sulphurously smelling eggs, bubbly eggs (see pictures below) and abnormally coloured eggs are best not eaten.  The remaining pieces should be safe.

GROUP B. ● Other eggs up to 28 days after laying or not exceeding the shelf life indicated on the packaging:  ▶▶▶  STEP 7 

GROUP C. ● Eggs with an unknown laying date, more than 28 days old, or past the expiry date on the commercial packaging:  ▶▶▶  BEST NOT TO USE 

STEP 7: ● Crack each egg and pour the contents into a separate small, flat dish.  Smell the egg and examine it thoroughly.  If it smells unpleasantly or suspiciously, or if its appearance differs from Figure 1 above, discard (recycle, compost) the egg.  

USAGE 2: ● Compliant Group A eggs after step 7 are the least risky and acceptable for all purposes, including eating raw.  

USAGE 3: ● Compliant eggs of group B after step 7 shall only be used for cooking with deep heating.  From the boiling point, the temperature should not fall below 100 °C / 212 °F for at least 10 minutes (frying, baking, stewing...).


Blemishes, Rottenness and Other Defects of Eggs

Odour changes

One must learn to recognise the natural smell of raw and cooked eggs by direct experience - elaborate verbal descriptions are not practically helpful.  A trained nose can easily detect deviations from the normal.  Even an untrained diner will be struck by an overly sulphurous (caused by hydrogen sulphide, sulphane) whiff or a distinctly putrid smell.  We do not eat odour-spreading eggs or give them to animals.

Structural changes

A boiled egg should have a pure homogeneous white and a smoothly granular yolk.  Any foams, cavities, bubbles, etc·, are highly suspicious (Figure 5).

Colour changes

A raw egg is described in Figure 1 and in the adjacent text.  A cooked egg should have pure white albumen and yellow yolk.  A bluish, blackish or greenish ring may or may not attract attention at the interface between the white and yolk, which is a normal phenomenon.  (micro-amounts of natural hydrogen sulphide from the white react with iron stores on the yolk's surface; see Figure 6).  Other colourations are at least suspicion-worthy, and we prefer not to consume or feed discoloured eggs.

Fig∙ 5.  Bubbly egg.  The picture shows an egg under warranty that has successfully passed the swimming test.  However, after boiling, it looks like an astronomical snapshot of the Moon - the white is all cratered.  We could start philosophising about what it might have been affected by.  The results of laboratory analysis could be interesting too.  A quarter of an hour before rushing to work, the best choice is the option number three:  This cookery achievement belongs in the garbage, and we should better peel a second egg (or grab a replacement breakfast on the way).   

Interesting Exceptions and Rarities

Stinky egg as a delicacy

Asian hospitality may surprise many Americans or Europeans when they are presented with a blackened egg on precious porcelain.  The initial shock from the brownish to dark grey colour is followed by the rolling out of an ammonia and rotty odour of considerable intensity.  This is neither an ill-natured joke nor fiendishness.  The excursionist has just been graced with an oriental delicacy called the Century Egg (Chinese: Pidan or Peidaan - Wikipedia).  In reality, this creation does not mature for a hundred years but only for a few months, wrapped in a clay-like lytic mixture of selected mud, tea, lime, salt, ash and other admixtures.  It is also served in classy restaurants.

Red eggs

Another surprise may be a serving of crimson eggs (Chinese red eggs - Wikipedia).  These eggs are firstly hard-boiled, and then the shell is exposed to the dye.  The colourant penetrates through the eggshell and seeps into its white.  Eggs decorated in this way are a symbol of birth or good luck at a new start.  They are served with the shell on, especially when welcoming a newborn child or at birthday parties.  It is therefore not surprising that whole or quartered eggs cooked in soups, sauces or inside meat rolls will pick up all sorts of tints (purplish, green, brown) from the surrounding cucumbers, peppers, sausages or root vegetables.

Fig∙ 6.  Dyed egg.  The photograph shows a hard-boiled egg stained on purpose.  It is a symbolic Chinese celebratory snack.  Natural processes can form a greenish ring around the yolk, as seen in this perfectly normal egg.