Lecture 10 Flashcards
What is the trend in egg consumption in Canada?
Increase in 3.8%
-value of eggs also increased
How many egg farms were there ?
1143 registered farms
Which province produces the most eggs and the percentages?
Ontario 35.8%
Quebec 20.1%
Western Provinces & NWT 36.8%
Eastern provinces 7.3%
How large are chicken flocks normally?
average 22,479
-can be as low as a few 100 or as high as 400,000
What is the most popular breed of chicken?
White leghorn
-then Rhode Island reds
What are the 2 kinds of eggs on the market?
Table eggs: whole uncracked eggs
Processed eggs: cracked so are used and processed in other products
What does the national egg organization do?
Regulate egg farmers in all of Canada
Manage supply of eggs
Promotes eggs
Develops standards for egg farming
What is the difference between free run vs free range?
Run: able to run around in the barn
Ranges: Run around in barn and also have access to the outside weather permittting
What is the nutritive value of eggs?
13 essential vitamins and minerals
High quality protein (albumen)
- PDCAAS= 1 (very high quality protein)
- riboflavin
- selenium
Fat (Talk)
- Fe
- Vit A
- Choline
- Lutein
- Zeaxanthin
- cholesterol
What is the composition of an egg in %?
75% water 12% Protein 10% Fat 1% Carb 1% minerals
2/3 albumen
1/3 yolk
How much does an average egg weigh?
57g with shell
50g without shell
What does albumin contain?
1.2 the protein and other nutrient of the egg
What is the most common protein in eggs?
Albumen
What are the 3 major proteins in egg whites?
Ovalbumin
Ovomucin
Lysozyme
What is the pH of a fresh egg?
7-8.5
-loss of CO2 during storage decreases egg pH
What is ovalbumin?
Contributes to foaming
Denatured by heat
What is Ovomucin?
Viscous gel properties
Large molecule with fibre–like nature
Contributes to egg foam stability
What is lysozyme?
Antimicrobial enzyme that’s part of the innate immune system
Thermally stable up to 72C
pH range from 6-9
What is the composition of the protein?
Protein found in the. yolk
-Lipoproteins which have. emulsifying properties
What is the composition of lipids?
- Trigluycerides
- Phospholipids
- Cholesterol (186mg)
- taste mainly
what gives the yolk its colour?
Exanthophil (colour pigment)
-not changed to Vit A in the body
Deep yellow colour has Vit A already in it
Pale yolk has Vit A added to it
Who is recommended to limit their egg consumption?
People with:
- high cholesterol
- Diabetes
- Cardio
limiting their cholesterol intake to 1-2egg/week
What are the main structures of the egg?
Shell Shell Membrane Air cell Thin albumen Thick albumen Chalazae Yolk Yolk membrane
What is special about the egg shell?
Shell is porous. to allow for gas exchange and can lose moisture
What is the air cell?
Bigger the air cell the less fresh the egg is
What are the characteristics of a fresh egg?
When broken it keeps rounded form due to viscosity of thick portion of white
Cloudy or milk white sure to dissolved CO2 shortly after laying
What are deterioration characteristics of an egg (aging)?
Thinning whites Flatter yolks Weaker chalazae Larger air cell Greater alkalinity
How is the quality of an egg impacted?
Flavour and odour determined by feed and type of hen as well as storage
- microorganisms
- environment packaging
If properly refrigerated how long should eggs last?
3-5 weeks after purchase
What is commercial cold storage?
~0C, just above freezing point 85-90% Humidity Circulation, free of objectionable odours Controlled atmosphere of CO2 or O2 Maintained quality for 6 months
What is candling?
Holding anew up to a strong light in a dark room to measure the interior quality of an egg
In candling what qualities are we looking for?
Quality of shell Size of air cell Position and mobility of yolk Blood spots Molds Fertilized
What is the grading system for eggs?
Canada A
Canada B
Canada C
What is a grade A egg used for?
Grocery stores
When candling should see a firm albumen, indistinct yolk outline, rounded centred yolk and air cell <5mm
Shell should have less than 3 stain spots and uncracked
What is a grade B egg used for?
Commercial baking
When candling should see yolk floats freely when twirled, germ development, oblong shape yolk, air cell <9mm
Shell should have stain spots less than 320mm, and uncracked
What is a grade C egg used for?
Commercially process foods
When candling should see prominent yolk outline and blood sports less than 3mm
Shell should have stain sport less than 1/3 of the shells surface and cracked but not leaking
What are the different sizes that eggs come in?
Jumbo at least 70g XL at least 63g Large at least 56g -most recipes standardized for this Medium at least 49g Small 42g
Where can eggs get salmonella?
On the egg shell via:
-infection of chickens reproductive system (inside the intact shell as the egg is being formed)
-Contamination on exterior of shell (moves through the shell pores to the white and yolk)
Why do we refrigerate eggs?
Helps to slow the aging process and prevent the rapid growth of bacteria
-should also rapid cool after egg has been laid
What is the difference between Canadian and European eggs?
Canadian:
- refrigerated
- chickens not vaccines
- pasteurization of eggs
European
- Not refrigerated
- chickens vaccinated
- egg not pasteurized
What are the 3 forms of killing off bacteria for eggs?
- Radio Frequency waves
- Hot water immersion, microwave, irradiation
- Under investigaiton
What is Radio frequency ?
Patented Kills salmonella and ecoli Hot water and RF energy Fast and low cost -egg is a little more mushy from this method when you cook it, egg is not fluffy and won't whip well
What is Hot water immersion, microwave, irradiation ?
Longer and more expensive
Potential denaturation and coagulation
Decreased whipping ability
What is under investigation?
HHP (high hydrostatic pressure)
High moisture and hot air
-helps to maintain characteristics of the egg so it does have better whipping ability
Why are there there products removed from the shell?
Convenient Easy to handle and store Pasteurized Can have separate white, yolks or both in one Free of salmonella No shell contamination Good for food service
What happens when you freeze eggs?
Functional properties intact
When thawed you get viscous and gummy texture
-should mix with sugar, salt, syrup before freezing
What happens when you have dried eggs?
Stay dried to have a doing shelf life
Required in dry mix products
Remove any glucose to retain Quality
Low moisture and cool conditions
What do egg substitutes not have?
Do not contain yolk but have high concentration of whites
-add corn oil, nonfat dry milk, soy protein isolate and soy bean old for yolk like properties
-these products have low cholesterol, fat and salt
Where do we see changes with heat coagulation of egg proteins?
Thickening Gel formation Opacity Insoluble Gradual Denature anda aggregate to form 3D gel network
When denatured proteins interact what to they form?
Bonds and a network stabilized by cross linking (including disulphide bonds)
At what temperatures to egg white, yolk and whole egg coagulate at?
White 60C
Yolk 65C
Whole 80C
What happens when you heat an egg fast vs slowly?
Slowly reduces curdling
Fast with high heat results in immediate curdling
What happens when you heal whites beyond coagulation point?
The protein shrinks and becomes tougher
What happens to heat coagulation of egg proteins when you add sugar, salt and acid?
Sugar: increases heat stability of proteins, used in custards
-higher coagulation temp by increasing heat stability
Salt: Promote coagulation or gel formation
Acid: Coagulate at lower temp
- Firmer
- too much may cause curdling
- minima hardness at pH6 but increases as pH decreases
What are the steps to coagulation by mechanical beating and egg foams?
Dispersion of air in liquid
- proteins unfold and surround air cells as a viscoelastic film around the bubbles
- Protein absorbs at the hydrophobic surface of air bubble with more proteins unfolding on the air bubble surface as the whipping time increases
- S-S disulphide linkages forms
What is globulin protein responsible for?
High formability of egg whites when beaten
What is albumen protein responsible for?
Surrounding the air bubble to help stabilize the bubbles in the foam
What can affect the bubble size and the foam?
Protein content
Whipping time
What does protein unfolding increase with?
Moderate decrease in pH
What are 4 stages of whipped egg whites?
Foamy -mostly liquid with some bubbles Soft peaks -White and hold shape but peaks will slump Firm Peaks -Peaks remain straight Over beaten -foam collapses, gets grainy watery and flat
What happens to the fine particles when over beaten?
Fine particles become more climbed together and are drier
When whipping eggs what can impact the quality?
Freshness
Temp
Type of beater
Bowl
What are some factor to improve egg foams?
- Pasteurization and spray drying of egg whites (partial unfolding of egg protein)
- Thick whites produce a more stable foam and increase volume of cooked products
- Room temp whites will whip easily and quickly and to a larger volume (due to lower surface tension at air-water interface)
- Fine wire beater will create smaller air cells
- Small rounded bottom bowl with sloping sides if using a mixer
- Large, wide bowl for hand mixing to allow for rapid vigorous mixing
- Copper bowl has increased resistance to foam breakdown due to copper-conalbumin complex
What are factors decrease egg foam quality?
- Egg yolk contamination- (fat interferes with foaming
- Over beating
- over coagulated
- loss of flexibility in the films and the braking of Manu air cell
- Decreased foam volume and stability
- Brittle and inelastic
- Will not blend well with other ingredients
- Liquid will separate from foam
What effect does sugar have on egg foam quality?
Sugar: stabilizes foam, reduces over beating
- texture fine, shiny/satiny appearance
- Slows coagulation resulting in longer beating time, add after foam created
- Adding too qwuicksl can result in loss of air from the foam
What effect does acid have on egg foam quality?
Moderate pH lowering ~5 Increased protein unfolding Increased albumen hydrophobicity Improved ovomucin foaming stability Cream of tartar Add after foamy stage as they reduce coagulation
What effect does salt have on egg foam quality?
decreases volume and stability and increases whipping time due to ions disrupting foam formation
Added after foamy stage
What is the functional uses of eggs in food?
Binding Leavening Thickener/gelling Glaze Clarify Slows crystallization Emulsifier Colour Flavour Nutritional Value
Which emulsions do lecithin and cholesterol promote?
Lecithin: oil in water
Cholesterol: water in oil
Why top eggs turn green?
Fe in yolk reacts with hydrogen sulphide in albumin to produce ferrous sulphide
- holding too long
- over cooking
- more likely to occur in older egg cause pH is higher
What prevents and egg from turning green?
Citric acid
