Eggs Flashcards
Best way to distinguish freshness of egg
Seeing if egg sinks of floats is best way
What happens to the egg as it ages?
Air increases in size and can migrate to the side of the egg
What is the best way of keeping eggs fresh?
Store in carton not door so less air introduced into the cell
Albumin
Thick and thin components of albumin
What is obvious when you crack a fresh egg open onto a plate?
Thick albumin is obvious thick and tall as it surrounds the egg
Colour of the shell and nutrition
Colour of shell is no impact on nutrition value of the egg, just due to breed of the hen that lays the egg
White egg hens
Leg Horn Hens
Brown egg hens
Rhode Island Red Hens
Colour of yolk
Varies with feed of the hen, but doesn’t indicate nutritive content
What is the yolk a major source of?
Vitamins, minerals, and fat
What is a chalazae?
Twisted cordlike strands of egg white
What does the chalazae do?
Anchor yolk in center of the egg
What does the prominent chalazae of the egg indicate?
Prominent chalazae indicates freshness
What is the air pocket of the egg
Pocket of air formed at large end of egg
What is the air cell caused by?
Contraction of the contents during cooling after laying
What are the two membranes of the shell?
Inner and outer shell membranes surround the albumen
Where does the air cell form?
Between these two membranes
Where is the thin albumen?
Nearest to the shell and spreads around thick white of high quality eff
Colour of thin albumen?
White
Colour of thick albumen
White
What is thick albumen a source of?
Major source of egg riboflavin and protein. Stands higher and spreads less than thin white in high-grade eggs
When do thins become indistinguishable?
In lower grade eggs
What are differences in nutrition composition of the eggs related to?
The diet of the hens
Where does pale colours of the yolk comes from?
Hans that are provided a wheat diet
When is the yolk more intense?
If the diet predominant in corn
When is yolk more orange in colour?
Carotenoids and betacarotene or fortifying feed with carotene
PH of egg yolk
pH of yolk is 6- 6.2
PH of egg white
on the alkaline side of the pH scale. Egg white tends to be 7.6 - 7.9
What happens when the chalazae becomes weakened?
The yolk then can shift its position and is no longer centered and can more towards one of the sides. You will notice that when you hard boil eggs
Size of the egg from start of laying cycle to end end
The size of the egg changes from the start to the end of laying cycle from a small egg to an extra large or jumbo egg
The larger the egg what happens to the shell
The larger the egg has a greater tendency for weakness in the shell
Why may jumbo or extra large eggs be lower quality?
Jumbos or extra large may have lower quality due to being more fragile
Why is the health of eggs important?
Need to ensure that there is control in lighting, temperature, water availability, and maintaining a clean environmental.
Process of egg production
Egg production farm
Egg collection process
Egg pickup from producer
Washing eggs
Candling eggs
Weighing and sizing eggs
Egg packaging
Washing eggs
Making sure they’re clean and no fecal material
What is candling eggs?
Using candlelight to image the interior structures. Air shell, chalazae, position of the yolk
Focuses on quality of egg
Egg packaging
Strength of calcium that makes up the egg shell means that you can push from end to end with force and it will not break. Allows us to stack them on top of one another
What is the grey ring around hard cooked egg yolk?
Ferrous sulfied that gives eggs the grey colour
What is present in yolk vs white contain?
Iron in yolk and hydrogen sulfide in white
What does hydrogen sulfide do?
will diffuse from egg white to surface of yolk where it will interact with the iron of the yolk and when H2S interacts with the iron of the yolk this si where you get ferrous sulfide
What is the grey rings in eggs more obvious in?
more stale eggs. Especially when you cool them slowly instead of rapidly
Where are eggs sold by the producer?
To a grading station for sorting according to size and grade
What does mass of egg determine?
Size
What does size of egg include?
Includes the shell of the egg which is different from the nutrition value.
What sized eggs can be grade A?
Possible for any egg sizes to be designated Grade A
What do egg grades depend on?
A,B, C
Position of yolk
Size of air cell
Quality of shell
What do egg grades depend on?
A,B, C
Position of yolk
Size of air cell
Quality of shell
Position of yolk
Centered and anchored by chalazae
Size of air cell
Small and centered at wide end
Quality of shell
Strong and thick
How long does it take from the egg to go from the hen to retail?
Typically takes 5 to 7
Distribution of eggs: Retail sales
55.1%
Distribution of eggs: hotels, restaurants, and institutions
27.6%
Distribution of eggs: Industrial Processors
17.3%
Industrial processors
turned into dried eggs for cake mix, egg whites, egg bites etc
Egg white proteins
Ovalbumin
Ovotransferrin
Ovomucoid
Ovomucin
Ovalbumin egg white composition
54%
Type of protein is ovalbumin
Simple protein (polypeptide chain on its own)
Ovalbumin solubility
Water solubility
Structure of ovalbumin
Solid gel and opaque
What does heat do for ovalbumin ?
denatured with formation of solid water holding gel that is opaque in nature
Percent of ovotransferrin in eggs
12%
What does ovotransferrin bind?
Bind Fe 2+/3+
Ovotransferrin where does it come into play?
iron interactions in yolk and white and that is where ovotransferrin comes into play and it capable of interacting with Fe 2+ or 3+
Percent that ovomucoid makes up?
11%
What kind of protein is ovomucoid?
Glycoprotein
What is ovomucoid subject to?
Subject to post translational modification
With one sugar added on to the peptide chain
Percent of ovomucin?
3.5%
Characteristics of ovomucin
Glycoprotein and filamentous
Where is ovomucin present?
in thick albumin at a 4x greater concentration than in the thin albumin
What does ovomucin allow?
Allows thick albumin to stand up and be distinct
Ph as eggs age
pH change due to carbon dioxide.
Part of thick albumin being less obvious is change in ovomucin as a result of the change in pH
Proteins in egg yolk
Lipoproteins
What do lipoproteins contains in their structure?
Phospholipids within their structure and phospholipids are stabilizers
Cell membrane of lipoproteins
cell membrane structure with the hydrophilic head and hydrophobic tail
What does the structure of lipoproteins make them?
An emulsifier
Lipoproteins lecithin
The generic term by phosphotidal choline is more scientific name
What does cooking with eggs center around?
Centres around coagulation of egg proteins
Temperature of cooking egg whites
62- 65 degrees C
Tempature of cooking egg yolds
65-70 degrees C
Temperature denatures for eggs
Whites and yolks differ
What makes the difference in cooking temperature?
Yolk has significant proportion of lipid which makes a different in temperature of coagulation and denaturation
Dilution
Increase in temperature for denaturation
What will dilution increase?
The temperature for denaturation/coagulation to occur
Direct heatings vs indirect heating and denaturation
Direct heat will cause the proteins to denature a lot quicker opposed to the water bath for custard which allow proteins to unfold more slowly and binding moisture in the thickening or coagulation process
Methods of egg agitation with cooking
Slow and uniform coagulation (liquid, soft stirred custard)
Liquid vs gel form of eggs
Liquid when agitates and gel when not agitated
What process if responsible for the thickened consistency of stirred custard?
Unfolding proteins, exposing the different regions of the polypeptides chains. If they polypeptide regions are hydrophilic you can see how they can easily bind the moisture which would be responsible for the thickened consistency of the stirred custard
What is formed in the absence of agitation?
Production of a moisture biding gel (semi-solid) product
What affect will sugar have on egg?
Protective effect on proteins requiring greater temperatures for proteins to denature
Effect of salt on egg?
Salt charged ions can actually enhance denaturation of proteins by virtue of their charges they can interact with amino acid residues of protein (side chains) and encourage the denaturation of the protein mixture. Minor or small effect because you don’t add a lot of salt to most of your products.
Soft custard process
Talking about indirect method of heating, the presence of sugar will increase temperature required for denaturation because of its hydrophilic nature and capacity to bind water it causes proteins to denature at higher temperature. We want to have a soft liquid or loose texture to soft custards and need constant stirring to prevent gel formation. Just thickened but do not want a gel in the soft custard. Key proteins that give us thickening are egg proteins (mostly egg white but also egg yolk) thicken by unfolding and binding water
Baked custard process
Coagulation going from a sol (water soluble native state of proteins in egg and milk mixure) converted into a semi solid moisture holding gel. order to get the gel you cannot stir or agitation the product. It needs to sit in the water bath undisturbed
When does curdling happens
Curdling happens with extensive and prolonged heating of our mixtures.
What is curdling the result of?
Overdenaturation of proteins so they no longer bind moisture
Characteristics of curdling
Clumps of protein have separated from the aqueous environment. Clear separation of denatures protein from aqueous surroundings.
Proteins interact with what in coagulation
Proteins interact with each other not water so they precipitate or fall out of solution.
What temperature do changes in thickening happen?
Changes in thickening as the temperature gets over 70 C. We will see thickening and coagulation around this time
Degrees of safety for flow heating vs branding up heat quickly
Slow heating gives five degrees of safety but quickly brining up heat bring 3 degrees of sagety. 5 vs 3 is difference between coagulation and curdling
What is the key to baked custard?
??? ** listen to video**
Even coagulation from constant stirring which will give you a thickened fluid custard and zero agitation is key to baked custard because the slow denaturation due to the water bath allows proteins to slowly unfold and form a network with the water
