This document discusses the functional properties of physically, chemically, and enzymatically modified milk proteins. It begins by defining functional properties as those physical and chemical properties that affect a protein's behavior in food systems. Factors like temperature, pH, water, and ions can impact functional properties. Modification is required to broaden a protein's range of functions or improve properties. Physical modifications like thermal treatments, ultrasound, and high pressure processing can impact structure and functional characteristics. Chemical modifications through acylation, phosphorylation, glycosylation, and deamidation can improve solubility, water binding, and emulsification properties. Enzymatic modifications through limited hydrolysis can increase solubility, emulsification, foaming, and gelation abilities while

1. Functional characteristics of physical, chemical and
enzymatic modified milk proteins
- Ramani Akshay R.
- Dairy Chemistry Division

2. WHAT IS FUNCTIONAL PROPERTIES ?
“Those physical and chemical properties of proteins that
affect their behavior in food systems during preparation,
processing, storage and consumption, and contribute to the
quality and organoleptic attributes of food systems”

3. Intrinsic Extrinsic Process
Composition of protein Temperature & pH Heating
Surface charge Oxido-reductase status Acidification
flexibility Water Drying
Structures Ions Enzymatic modifications
pI of protein Lipid Storage conditions
Bound flavor ligands Gum Reducing conditions
Hydrophobicity/ hydrophilicity Surfactant
FACTORS AFFECTING FUNCTIONAL PROPERTIES
OF PROTEINS

4. WHY MODIFICATION IS REQUIRED ?
 Due to the inherent structural limitations in some food proteins, they lack
the requisite physico-chemical properties to serve a function in foods.
 Other proteins are excellent in one functional aspect but may be poor in
another but can be modified to have a broader range of function.
 To meet the complex needs of the manufactured food products.

5. MODIFICATIONS
PHYSICAL CHEMICAL ENZYMATIC
 Temp
 Radiation
 High Pressure
 Acylation
 Phosphorylation
 Sulfitolysis
 Glycosylation
 Enzymatic hydrolysis
 Plastein reaction
 Protein cross linking
Improved Functional and nutritional properties

6. FUNCTIONAL CHARACTERISTICS
OF PHYSICAL MODIFICATION OF MILK PROTEIN

7.  Pasteurization did not affect the secondary structure of whey
proteins nor disturb the supramolecular structure of the casein
micelles.
 High temperatures caused loss of the secondary structure,
disrupted the tertiary structure, unfolding and/or aggregation of
whey proteins. It also induced the solubilization of colloidal
calcium phosphate and CMs aggregation.
Thermal treatment
- (Nunes, et al., 2019)

8.  Decrease in the size of the powder particle and consequent improvement of the rehydration
process.
 For example,
Native casein micelles have an average hydrodynamic diameter of 150–200 nm, sodium
caseinate approximately 60–65 nm and whey proteins less than 10 nm. After ultrasound
treatments,
 A decrease from 28 μm to 0.1 μm in the particle size of rehydrated MPC (20 kHz-2 min).
 A decrease from 433 to 72 nm for WPI, from 956 to 256 nm for MPI and from 245 to 58 nm
for NaCas during rehydration (20 kHz-120 s).
 A decrease from 508 μm to 286 μm for rehydrated WPI and from 324 to 1.0 μm for
rehydrated WPC (20 kHz-30 min).
Ultrasound
- (Nunes, et al., 2019)

9.  Superficial hydrophobicity increased.
 The hardness of casein and whey protein gels, as well as the
stability of formed emulsions and foams, increased.
High-pressure processing
- (Nunes, et al., 2019)

10. FUNCTIONAL CHARACTERISTICS
OF CHEMICAL MODIFICATION OF MILK PROTEIN

11. ACYLATION & SUCCINYLATION
 Blocking of amino group
 Increase in protein solubility in weak acidic, neutral and alkaline solutions (lower pI)
 Increase or decrease in water holding capacity
 Changed emulsification and foaming properties
- (Chobert, 2010)

12. PHOSPHORYLATION
 Improved or impaired by phosphorylation.
 Improved water solubility of zein between pH 2-9.
 Decrease in water solubility, due to protein cross-linking. (e.g.casein and soybean glycinin)
 Decrease in emulsifying activity of casein and increase in zein soy protein isolate.
 Improved gelation properties due to cross-linking of proteins (caseinandgluten).
- (Damodaran, 1996)

13. GLYCOSYLATION
 Change the secondary and tertiary structures and the hydrophobicity.
 Increased solubility of protein in the range of their isoelectric points.
 Increase in the flexibility and unfolded state.
 Better foaming capacity and stability.
 Improvement of surface properties and protection against denaturation.
- (Damodaran, 1996)

14. DEAMIDATION
 Substantially improved solubility,
 Water binding capacity,
 Foam expansion,
 Emulsion viscosity as compared to their unmodified counter parts
- (Kumagai, 2012)

15. FUNCTIONAL CHARACTERISTICS
OF ENZYMATIC MODIFICATION OF MILK PROTEIN

16. SOLUBILITY
 Caseins are least soluble at their isoelectric point (pI) of 4.6, which limits their use in high
acid foods and beverages.
 Whey proteins have very good solubility over a wide pH range but denaturation tends to
decrease their solubility at low pH as a result of increased aggregation.
 Partial hydrolysis of protein increases the solubility.

17. EMULSIFICATION
 Peptides with a molecular mass greater than 5 kD are reported as being highly efficient at
improving emulsifying properties.
 Limited hydrolysis (DH 2 and 6.7%) of casein decrease the emulsifying activity (EA) at all
pH whereas the emulsion stability (ES) at DH= 2% is higher than native casein.
 The EA of casein decrease with increasing net charge and with the decreasing hydrophobicity.
 Limited proteolysis of globular proteins increase EA and ES due to exposure of buried
hydrophobic groups.
 The excessive digestion results in loss of globular structure and optimum size of split peptides
leading to unstable emulsion

18. FOAMING
 Surfactants like proteins or peptides stabilize air-water interface and help information of
foam.
 Limited proteolysis yields peptides with improved foaming properties.
 Low molecular weight peptides appear to exhibit higher foaming properties than larger
peptides or native proteins.

19. GELATION
 A structural network that maintains shape, has mechanical strength, viscoelasticity and
retains entrapped water with minimum syneresis.
 Near their pl, proteins form opaque particulate gels where as fine-stranded, transparent and
homo generous gels are formed from proteins at pH values distant from their pl.
 The increased net charge on the protein results in increased charge repulsion between
peptides, decreasing gelling ability.

20. ENZYMATIC CROSS –LINKING
 Modification of textural and water binding properties of milk products.
 Introduction of covalent bond, Increase in gel firmness and sensory properties in yogurt like
fermented products especially, in low fat or protein products.
- (Buchert, et al., 2010)

21. Proteins are fundamentally important as nutrients but now they are seen to be
much more.
Most proteins still have scope for further improvement in their physical and
functional properties.
Chemical modification is not very desirable for food applications.
Enzymes have long been used for modifying food proteins and their use is many
times more acceptable to improve the physical and functional properties of
proteins.
Conclusion

22. Thank you-
Your valuable suggestion
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23.  Nunes, L. andTavares, G. M. (2019). Thermal treatments and emerging technologies: Impacts on the structure and
techno-functional properties of milk proteins. Trends in food science & technology, 90, 88-99.
 Schwenke, K.D. (1997). Enzyme and chemical modification of proteins. In Food Proteins and Their Applications (Eds
Damodaran, S. & Paraf, A.), Food Science and Technology (Marcel Dekker, Inc.) pp393-423.
 Damodaran, S. (1996) Amino Acids, Peptides, and Proteins In Food Chemistry (Ed Owen R. Fennema) 3rd edn, Marcel
Dekker, Inc.) pp417-425
 Chobert, J.M. (2010) Milk protein tailoring to improve functional and biological properties J. Bio Sci. Biotech. 2012,
1(3): 171-197
 Buchert, J. (2010) Crosslinking Food Proteins for Improved Functionality Annu. Rev. Food Sci. Technol 2010.1:113-138.
References:

24. Functional properties of proteins in foods