The document discusses the sources, structures, and functional properties of proteins, highlighting the differences between plant and animal proteins in terms of digestibility and amino acid completeness. It explains protein denaturation, its causes, and the effects on solubility and functionality in food systems, such as gelation, emulsification, and foaming. Additionally, it touches on the factors affecting protein quality and characteristics critical to food processing and preparation.

1. “SOURCES,DENATURATIO
N AND FUNCTIONAL
PROPERTIES OF
PROTEINS”
SUBMITTED BY,
SHAHNAZ MOL.A

2. PROTEIN ?
“ Proteins are large
Biological Molecules or
Macromolecules consisting of
one or more long chains of
amino acid residues. ”

3. BASIC AMINOACID
STRUCTURE

4. SOURCES OF
PROTEIN

5. PLANT PROTEIN
.Derived from plant sources.
➔Eg: Pulses
Cereals
Nuts
Beans
Vegetables
Soy products
.Plant Proteins are less digestible.

6. ● Plant proteins are Biologically Incomplete,
Because..................
“FOOD LACKS ONE OR MORE
ESSENTIAL AMINOACIDS
NEEDED BY THE BODY.”

7. EXAMPLE:
“IN LEGUMES THE
ESSENTIAL AMINOACID
METHIONINE IS
ABSENT.”

8. AND ALSO..
“IN GRAINS THE
ESSENTIAL
AMINOACID LYSINE
IS ABSENT”

9. ● An incomplete protein can be converted into a
complete protein, if two incomplete proteins are
added together called complementarity of proteins.
+ +
=
BY THIS,WE CAN GET AN
ADEQUATE SUBSTITUTE OF
ANIMAL PROTEIN

10. ANIMAL PROTEIN
➔Derived from Animal sources.
➔Example:
● Egg
● Meat
● Milk
● Fish
● Liver
● Kidney
● Brain
● Heart
● Sweetbreads

11. ● Animal proteins are Biologically Complete,
Because.....
“FOOD CONTAINS ALL THE
9 ESSENTIAL AMINOACID
NEEDED BY THE BODY.”

12. PLANT VS ANIMAL
PROTEIN
PER 100g

13. “CHICKEN
CONTAINS
31g of
protein”
“PEANUT
CONTAINS
25g OF

14. “TUNA
CONTAINS 29g
OF PROTEIN”
“ALMONDS
CONTAINS 21g
OF PROTEINS”

15. “EGG
CONTAINS
OF 12.5g
OF
PROTEIN”
“CAULIFLOWER
CONTAINS 2g
OF PROTEIN”

16. MEASURE OF PROTEIN
QUALITY
Biological Value (BV) of Protein
●
– based on NITROGEN RETENTION
●
– higher the protein quality= more Nitrogen
retained= more protein synthesis than catabolism
●
BV of EGG protein = 100%, all absorbed protein
retained.

17. DENATURATION
● IUPAC definition
“Process of partial or total
alteration of the native
secondary, and/or tertiary,
and/or quaternary structures
of proteins resulting in the
loss of bioactivity.”

18. BONDS WHICH
STABILISES THE
STRUCTURE OF PROTEIN.
● Disulphide bond.
● Salt bridge
● Hydrogen bond

19. DISULFIDE BOND

20. SALT BRIDGE

21. HYDROGEN BOND

22. AFTER DENATURATION

23. DENATURATION RESULTS IN..
● Decrease in solubility
● Increase in viscosity
● Altered functional properties
● Loss of enzymatic activity
● Sometimes increased digestibility
OF PROTEIN.

24. FACTORS CAUSING
PROTEIN DENATURATION.
● pH.
● Temperature.
● By Heavy Metal Ions.
● By Small Polar Molecules.

25. pH
● Affects salt bridge.
● Neutralise the charge of one of the ionically bonded
ion.
● Hence the bond is broken.

26. TEMPERATURE
● High temperature destabilizes
the non-covalent interactions
holding the protein together
causing it to eventually unfold
(to denature).

27. ● As the temperature increases, Bonds are broken in
the following order :
➔ Hydrogen Bond
➔ Ionic Bond

28. METAL IONS
● Since metal salts are ionic they disrupt salt bridges
in proteins. The reaction of a heavy metal salt with a
protein usually leads to an insoluble metal protein
salt.
● Heavy metals may also disrupt disulfide bonds
because of their high affinity and attraction for
sulfur and will also lead to the denaturation of
proteins.

29. SMALL POLAR MOLECULE
● Urea in concentrated solution will denaturate
protein.
● It disrupts the hydrogen bonds and cause complete
Denaturation.

30. FUNCTIONAL PROPERTIES
OF PROTEIN IN FOOD

31. “Those physical and chemical properties,
which affect the behavior of proteins in
food systems during storage, processing,
preparation and consumption. It is these
characteristics, which influence the ‘quality’
and organoleptic attributes in food.”
IT IS DEFINED AS..

32. 1)SOLUBILITY
● Functional properties of proteins depend on their
solubility
● Affected by the balance of hydrophobic and hydrophilic
amino acids on its surface
● Charged amino acids play the most important role in
keeping the protein soluble
● The proteins are least soluble at their Isoelectronic
point(no net charge)
● The protein become increasingly soluble as pH is
increased or decreased away from the Isoelectric point

33. Contd..
● Salt concentration (ionic strength) is also very important
for protein solubility
● At low salt concentrations protein solubility increases
(salting-in)
● At high salt concentrations protein solubility decreases
(salting-out)
● Denaturation of the protein can both increase or
decrease solubility of proteins
● Eg in very high and low pH denature, the protein is
soluble since there is much repulsion.

34. ● Very high or very low temperature on the other hand
will lead to loss in solubility since exposed
hydrophobic groups of the denatured protein lead to
aggregation (may be desirable or undesirable in food
products).

35. 2)GELATION
● A Gel is a mixture of mostly fluids locked in a tangled
mass of denatured and coagulated proteins. The liquid
keeps the proteins from collapsing and the protein keep the
liquid from flowing away.
● Texture, quality and sensory attributes of many foods
depend on protein Gelation on processing.
Eg: Sausages, cheese, yogurt, custard
● Gel; a continuous 3D network of proteins that entraps
water.
● A gel can form when proteins are denatured by Heat, pH,
Pressure and Shearing by aggregation and interaction with
other proteins.

36. 3)EMULSIFICATION
● Emulsions consist of two liquids that are
immiscible, where one of the liquids is dispersed in
the other in form of small droplets.
● Proteins can be excellent emulsifiers because they
contain both Hydrophobic and Hydrophilic groups.
● Factor that affect protein-based emulsions is the type
of protein.
● Increased surface hydrophobicity will increase
emulsifying properties.
● Increased solubility increases emulsification ability.

37. 4)FOAMING
● Foams are very similar to emulsion where air is the
hydrophobic phase instead of oil
● Principle of foam formation is similar to that of
emulsion formation (most of the same factors are
important)
● Foams are typically formed by Injecting gas/air into a
solution through small orifices or
● Mechanically agitate a protein solution (whipping) or
● Gas release in food, eg: leavened breads (a special
case)

38. ● Increasing salt usually improves foaming since
charges are neutralized (they lose solubility)-
salting-out) in Egg albumins.
● Increased salt negatively affect foaming (they get
more soluble-salting in).
● The farther from pH the more repulsion and the
foam breaks down.

39. REFERENCE
● chapter 5 protein. pdf
● S. Johanna, “Functional properties of legume
protein compared to egg protein and their
potential as egg replacers in veg food” pp 3-6.