1. Dr. Abdur Rahman Department of Industrial Biotechnology
PROTEINS OF FOOD
Dr. Abdur Rahman
Department of Industrial Biotechnology

2. CONTENTS Recap Amino acids Types of amino acids Structure of proteins
Role of proteins in different food formulations
Baking (Breads, Cakes)
Browning
Pasta

3. RECAP Proteins play important roles in human body
Structural role : Proteins in connective tissues, collagen and elastin
Contractile function / role in movement : Contractile proteins like actin and myosin play important role in movement of body
Regulatory Proteins
Enzymes : play v important role in different body functions from cellular level to system level, enzymes involved in digestion of food to metabolism at cellular level
Immune system : antibodies are proteins produced by immune system to fight infections
Transport proteins : haemoglobins
Hormones : regualtion of different metabolisms like insulin for glucose regulation

4. RECAP What are proteins composed of?
The basic structural unit of proteins is amino acids
There are 20 different types of amino acids which contribute to the structure of different proteins

5. RECAP Amino acids : acid or base?
German word for hybrid ion : Zwitterions :
A zwitterion is a compound with no overall electrical charge, but which contains separate parts which are positively and negatively charged
The amino acid residues in proteins are L Stereoisomers

6. PEPTIDE
Peptide : Chains of amino acids, linked with a petide bond

7. N terminal and C terminal
Amino terminal end N terminal
Carboxy terminal end C terminal

8. Oligopeptides and Polypeptides
Depending on the number of amino acid residues, dipeptide, tripeptide and so on and so forth – Oligopeptide
Peptides can be distinguished from their ionization behavior
Polypeptides

9. Levels of Protein Structure
Conceptual hierarchy of structure for understanding

10. Protein Chemistry

11. Levels of Protein Structure
Primary structure
Secondary structure
Tertiary structure
Quaternary structure

12. Levels of Protein Structure
The conceptual hierarchy of protein structure
Primary structure : Basic sequence of amino acids in a polypeptide chain
Secondary structure : refers to the local conformation of some part of a polypeptide
Tertiary structure : The overall three-dimensional arrangement of all atoms in a protein is referred to as the protein’s tertiary structure
Quaternary structure

13. Role of proteins in foods
Role of Proteins in bread?
Kneading : Addition of water causes hydration of gliadin and glutenin proteins, leads to the formation of gluten
Stress inducced during kneading breaks bonds between protein chains, allowing the chains to move and become realigned. The new bonds that are formed allow relaxation of the dough.

14. Role in Baking Proofing (Rising)
At this stage starch breakdowns and fermentation occurs.
CO2 produced and causes gluten network to expand
Leaves open cellular structure with gases trapped in pockets.
The effect of gluten quality and content will affect the quality of product, how?

15. Role in Baking
Baking
During baking the temperature is high, and the gluten coagulates.
As a result the gluten is no more elastic
Consequently the bread is firm but open and light in texture

16. Role in Baking Role of Egg Proteins in Baking?
Entrapment of air during beating
Form the film which entraps air and increase the volume

17. Role in fried foods
While the elastic quality of egg proteins is lost in cooked eggs, but the firmsing of proteins allows eggs to perform another important function, which is holding ingredients together.
Example : Crumb coating holds more tightly when its dipped in egg

18. Role in Colors and flavors (baking, frying etc)
The Maillard reaction is named after the French scientist Louis Camille Maillard ( ), who studied the reactions of amino acids and carbohydrates in 1912, as part of his PhD thesis, which was published in 1913
Maillard reaction is not a single reaction, but a complex series of reactions between amino acids and reducing sugars, usually at increased temperatures. Likecaramelization, it is a form of non-enzymatic browning.
In the process, hundreds of different flavour compounds are created. These compounds in turn break down to form yet more new flavour compounds, and so on. Each type of food has a very distinctive set of flavour compounds that are formed during the Maillard reaction.