Peptide
Bond Formation :
R1
H
R2
|
| |
H3N+ - CN
- C - OH + H – N –
CH – COO-
||
O
||(Remove H20)
R1
H R2
|
| |
H3N+ - CN -
C – N – CH – COO-
||
O
There is TWO main type of proteins can be found in food
v Gluten
v Egg proteins
|
Figure 1: Gluten (Canadian Grain Commission 2016)
|
Figure 2: Egg (NCPTT 2016) |
|
Ø Found
in the endosperm of
mature wheat grain
|
Figure 3: Gluten in the endosperm of wheat( Canadian Grain Commission 2016)
|
Function:
ü Use in dough formation :
ü Contains gliadins and glutenins ( Canadian Grain Commission
2016)
- Gliadins facilitate fluidity, extensibility, contribute
to bread-loaf volume.
- Glutenins is responsible for elasticity, cohesiveness and mixing
tolerance of dough.
ü Egg white - Albumin Protein (NCPTT
2016)
|
Figure 4: Content of Egg white (NCPTT 2016) |
Ø Ovalbumin
- the most abundant protein in egg white
Ø Ovotransferin
– act as a metal-chelating antioxidant , bind metallic ions
Ø Lysozyme
– act as an antibacterial shielf for the egg
Ø Ovomucin
– responsible for egg-white viscosity
Ø Phosvitin- Emulsifying activity (Samaraweera et al. 2011).
Ø Lecithin- Improve emulsification, texture and flavour.
Function of EGG PROTEIN:
|
Figure 5 : Function of Egg Protein (NCPTT 2016,Nii & Ishii 2005,American Egg Board 2016,Tarleton Academy 2016)
|
ü Coagulation
- Process
that results in loss of solubility or
a change from a fluid state to a solid state when it is exposed to heat or acid (NCPTT
2016).
o Egg
white begins to thicken at around 62 °C
o Egg yolk
begins to thicken at 65 °C
- - Can
affect the texture of food as it can act as a thickening agent due to the coagulation process (NCPTT
2016)
- - Sugar can delay the coagulation process (NCPTT 2016)
oIt can
decrease the rate of heat denaturation and increase the coagulation temperature.
- Salts promote coagulation
Figure 6: The process of protein coagulation(Socratic 2015).
ü Emulsification
- Egg yolk is a type of oil in water emulsion
- Lecithin is an emulsifying agent (Nii & Ishii
2005)
- Important
process in making salad dressings and whipped topping
Figure 6: The process of emulsifier functions in oil and water.
ü Foaming
- Bubbles will be trapped by
egg albumen and decrease in size, increase in number after whipping or
beating (American Egg Board 2016)
o Involve denaturation of protein at
an air-liquid interface
o then
hydrophobic part of the protein will enter the air
o the
hydrophilic part of the protein remains in the water (Athaualpa 2006)
o Globulins and ovomucin is
responsible for foaming properties of
the egg (NCPTT 2016)
- Salts
and lipids can reduce
foaming performance by reducing its stability thus the
bubbles formed will collapse more easily
- Sugar can improve stability of the food
product.
- It is important to dairy
desserts such as ice-cream and custard (American Egg Board 2016).
o Due
to its foaming properties
o It
can increase its volume
Figure 7: The process of foaming (A Dash Of Science 2013).
ü ü Enrichment
- To add colour and nutritional values in
sauce (Tarleton Academy 2016).
Figure 8: The process of maillard reaction.
Others function of Protein:
|
Figure6: Other Function of Protein ((Nii & Ishii 2005, Gorton 2012,British Nutrition Foundation 2016a,Tarleton Academy 2016, Food Info 1999 )
|
ü Emulsification
- Protein
is an amphiphilic substance
which contains hydrophobic part and hydrophilic part (Nii & Ishii 2005)
- Protein
can stabilize oil in water emulsion or air in water emulsion( Nii & Ishii
2005)
o by
diffusing to interface,
o unfold
o then
exposing the hydrophobic group
o and
interact with lipid
- Prevent droplet
coalescent ( separation of two immiscible phase)
- It is
important to salad dressing
ü Gelation
- Involves denaturation of proteins
- Gel
is a continuous network of macroscopic dimensions immersed in a liquid medium
and exhibit no steady-state flow due
to water immobilization (Gorton 2012).
- Gelation can make whey protein in the bakery product
starts to bind water and lead to a better mouthfeel and palatability (Gorton 2012).
- It
is important to bakery products
ü Bulking
- Some Protein can mimic the
sensory properties of meat
- Form the main part of the
filling of foods for vegetarians such as cottage pie (British Nutrition
Foundation 2016a)
- Eg. Texture Vegetable Protein
ü Glaze
- Enhance the colour of the
product
- Give products a shiny
glaze (Tarleton Academy 2016)
ü Maillard Reaction
- A type of non-enzymatic
browning
- Involve the reaction of simple sugars and amino acids
- Form brown nitrogenous polymers
which is called melanoidins (Food-Info 1999)
- Gives a desirable colour to bread crust and
cookies (Food Info 1999)
- Give a desirable flavour to coffee , cocoa
-
Reference:
A Dash Of Science 2013, How do egg whites make a foam?, viewed 11 November 2016,
<http://adashofscience.com/2013/04/04/egg-white-foams/>
American
Egg Board 2016, AERATION/FOAMING/STRUCTURE, viewed 8th November,
<http://www.aeb.org/food-manufacturers/eggs-product-overview/functional-properties/39-functional-properties/207-aeration-foaming-structure>
Athaualpa
R. 2006, “ALBUMEN PROTEIN AND FUNCTIONAL PROPERTIES OF GELATION AND FOAMING”,
viewed 7th November 2016, <
http://www.scielo.br/pdf/sa/v63n3/29835.pdf>.
British Nutrition
Foundation 2016a, Food Functions-Bulk, viewed 8th November
2016,http://www.foodafactoflife.org.uk/attachments/d12facea-6d5a-4f87b3289646.pdf
British Nutrition
Foundation 2016b, Food Functions-Glaze, viewed 8th
November<2016,http://www.foodafactoflife.org.uk/attachments/7d85f595-53bd-450e90df0edc.pdf>.
Canadian
Grain Commission 2016 ,Gluten's role in bread baking
performance, viewed 8th November 2016,<https://www.grainscanada.gc.ca/fact-fait/gluten-eng.htm>.
Gorton L. 2012, Protein's vital role
in baking , viewed 7th November 2016, <http://www.foodbusinessnews.net/articles/news_home/Supplier-Innovations/2012/12/Proteins_vital_role_in_baking.aspx?ID=%7B779890A3-9041-49F4-946A-7FDBB51FAE0D%7D>
NCPTT
2016, Protein Chemistry of Albumen Photographs , viewed 7th November
2016, <http://albumen.conservation-us.org/library/c20/messier1991a.html>
Nii
T., Ishii F 2005, “Dialkylphosphatidylcholine and egg yolk lecithin for
emulsification of various triglycerides” ,viewed 7th November
2016, <https://www.ncbi.nlm.nih.gov/pubmed/15748826>.
Samaraweera, H, Zhang, W, Lee, EJ, & Ahn, DU 2011, 'Egg Yolk Phosvitin and Functional
Phosphopeptides—Review', Journal of Food Science, vol.76, no.7, viewed 11 November 2016,
<http://www.aeb.org/images/Egg_Yolk_Phosvitin_and_Functional.pdf>
Socratic 2015, Can someone explain
to me the chemistry of cooking an egg, and how amino acids, functional groups
of proteins, and polymerization are used/completed?, viewed 11 November 2016,
<https://socratic.org/questions/can-someone-explain-to-me-the-chemistry-of-cooking-an-egg-and-how-amino-acids-fu>
Tarleton
Academy 2016, FUNCTIONS AND PROPERTIES OF
INGREDIENTS, viewed 7th November 2016,
<http://www.tarletonacademy.org/images/FUNCTIONS-AND-PROPERTIES-OF-INGREDIENTS.pdf>