There are mainly 3 types of changes due to the effect of heat .
The 3 changes are :
- Denaturation
- Coagulation
- Mailard Browning
Denaturation
The process of denaturation occurs when Proteins undergo a change in their structure.
When denaturation occurs , the bonds that holds the shape of the complex polypeptide chains break .
The original structure is then replaced by a looser , less compact structure .
Denaturation often affects the original properties of the Protein .
HEAT is the most common way of denaturing proteins . The extent and speed of protein denaturation depends on the structure of protein and the temperature applied .
Coagulation
Coagulation is the reaction in which a protein changes from LIQUID state to a semi-solid or solid state in the presence of HEAT , pressure or chemicals . In coagulation , protein molecules unfold , collide with each other and CLUMP TOGETHER to form a solid .
Coagulation is an irreversible reaction .
Examples of coagulation in food are :
- Cheese when heated to about 70 degress celcius become rubbery and tough .
- Milk proteins coagulates when milk is heated and form a "skin" on its surface .
- Protein albumin in egg whites denatures and coagulates at about 60 degress celcius , and the egg white turn solid and opaque . Egg yolk coagulates at 70 degrees celcius and becomes hard and crumbly upon further heating .
Mailard Browning .
Mailard Browning is a complex chemical reaction that occurs when foods containing SUGARS and proteins are HEATED . Upon heating , the proteins in food denautre and react with several compounds , resulting in a brown colouration seen on the surface of food . As a result , the flavour and aroma are greatly enhanced .
This reaction mainly occurs of temperatures above 150 degrees celcius . Effects of mailard browning can be seen on breads and roasted meats .
Thats all for the effects of heat on proteins ! I hope you have learnt something today :)
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