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