This document discusses colloidal systems found in food. It begins by defining mixtures, solutions, suspensions, and colloids. A colloid is a mixture with particle sizes between solutions and suspensions. Common colloidal systems in food include sols, gels, and emulsions. Sols have solid particles dispersed in a liquid, while gels are solidified sols. Emulsions disperse one liquid into another immiscible liquid. Food colloids are important for texture, structure, stability, and maintaining properties of food systems.

1. COLLOIDAL SYSTEMS IN
FOOD
PRESENTED BY:
MAMTA SAHURKAR
(FOOD TECHNOLOGY)
LAXMINARAYAN INSTITUTE OF
TECHNOLOGY,
NAGPUR

2. Mixtures
Is made up of two or more substances mixed together.
Chemical identity of components is retained and some
mixtures are easy to separate
Homogenous
mixtures
Compositions that
look same
throughout
Eg: Food colorings
and water
Heterogenous
mixtures
Not the same
throughout
Eg: oil and water
Colloids
Mixture consisting
of particles
between the size
of solutions and
suspensions
Eg: Milk
Suspensions
Particles are so
large that they
settle out unless
you stir
Eg: sand and
water
Solutions
Paticles are very
small can pass
through filter paper
Eg: food colouring
and water

3. Soluti
ons
Examples of solution are:
Fruit juices
Sugar and water syrups
Salt and water brine
• A solution is formed when
• A liquid is dissolved in another liquid.
• Eg: Fruit squash in water
• A solid is dissolved in liquid like sugar in cup of tea
• Solutions will not separate when left to stand.

4. Type of
Solutions
Solvent Examples

5. Terminolog
iesSolution:
• Homogenous mixtures of two or more substances
• A liquid mixture in which the minor component (the solute) is uniformly
distributed within the major component (the solvent).Eg: Salt in water,
Sugar in water.
Solute
• The minor component in a solution, dissolved in the solvent. Eg: Sugar in
sugar solution with water
Solvent
• A solvent is the component of a solution that is present in the greatest
amount. It is the substance in which the solute is dissolved. Eg: Water in
salt solution
Solute Solvent Solution

6. Solubility
Solute Temperature Solubility
Solid Increases Increases
Gas Increases Decreases
Solute Pressure Solubility
Solid Increases Remains same
Gas Increases Increases
Parameters affecting
solubility• Temperature
• Pressure
• Maximum amount of solute that can be
dissolved in a definite amount of solvent
at a specific temperature
• Referred to as: Ability to dissolve.

7. Nature of
Solvent/Solute• Like dissolves in
like
Solute type Non polar solvent Polar solvent
Non
polar(Fat/Grease)
Soluble( Soap) Insoluble(water)
Polar Insoluble Soluble(Water)
Ionic(Salt) Insoluble Soluble
• High solubility implies soluble
• Low solubility implies insoluble

8. Types of
solutions• An unsaturated solution is the one in which more solute can be dissolved
in a solvent at a given temperature
• A saturated solution is a solution containing maximum amount of solute
that will dissolve at a given temperature.
• A supersaturated solution is a solution that contains more solute that
would dissolve in a saturated solution at a given temperature.
Temperature
increases

9. COLLOIDS ???
• All prepared food dishes are examples of a
mixture known as a colloid.
• A colloid is a type of chemical mixture where
one substance is dispersed evenly throughout
another. Colloids are formed when one
substance is dispersed through another, but
does not combine to form a solution.
• There are many types of colloidal systems
depending on the state of the two substances
mixed together.
• The mixture of the two substances is called

10. Properties of colloids
• A colloid is a heterogeneous
mixture
• The size of colloidal particles is
small to be seen with naked
• The colloids are large enough
scatter beam of light passing
through it and making its path
visible
• They do not settle down if
undisturbed

11. Importance of colloids in foods
ProvidesTexture
Improves mouthfeel
Gives structure
Stability
Important for maintaining rheological
properties of food systems.
Eg: Whipped cream, Mayonnaise, milk,
Butter, Gelatin, Jelly.

12. COLLOIDAL SYSTEM
• A colloidal system consists of two separate phases:
• Dispersed phase (or internal phase)
• Continuous phase (or dispersion medium).
• A colloidal system may be solid, liquid, or gaseous.The
substance which is dispersed is known as the disperse
phase and is suspended in the continuous phase.
Liquid two phase system vigorously mixed
During mixing
During mixing

13. System Dimension
One phase system Below 1 mm
Colloid 1nm to 0.5 micrometer
Suspensions Above 0.5 micrometer
Colloidal
dispersions
lyophilic
lyophobic
(High affinity between
dispersed phase and
medium or solvent loving)
(Low affinity between
dispersed phase and
medium or solvent
repelling)
Classification based on
size

14. Main types of colloidal systems

15. Solutions
Particles
dissolve
Colloids
Particles
don’t
dissolve

16. • A sol is a colloidal solution suspension of very small solid particles in
a continuous liquid medium.
• Sols exhibit characteristic optical properties.
• They may have an opaque or clear appearance to the naked eye
when viewed under a microscope, but the dispersed particles are
sufficiently large to scatter and polarize the incident light to some
extent.
• This scattering of visible light by colloidal solution is known as Tyndall
effect.
• When viewed through an ultramicroscope, colloidal particles appear
to be in a state of rapid motion called Brownian motion.
SOL

18. Sol
• A colloid (aggregate of very fine particles dispersed in a
continuous medium) in which the particles are solid and
the dispersion medium is fluid.
• If the dispersion medium is water, the colloid may be
called a hydrosol; and if air, an aerosol.
• Lyophobic sols are characterized by particles that are not
strongly attracted to molecules of the dispersion medium
and that are relatively easily coagulated and precipitated.
• Lyophilic sols are more stable and more closely resemble
true solutions. Many sols are intermediate between
lyophobic and lyophilic types.

19. GEL
A gel is a solid jelly like material that can have
properties ranging from soft and weak to hard and
tough.
Gels are defined as a substantially dilute cross
linked system, which exhibits no flow when in the
steady-state.
By weight, gels are mostly liquid, yet they behave like
solids due to a three-dimensional cross-linked network
within the liquid. It is the crosslinking within the fluid
that gives a gel its structure (hardness) and
contributes to the adhesive stick

20. Sols and
GelsSols and Gels are both liquid loving (lyophilic colloids)
Sol
Liquid or colloid mixture in which solid particles are
dispersed in liquid phase. Dispersed phase is attracted
to molecules of continuous phase.
GEL.
Sometimes the mixture needs to be heated and stirred.
When this solution cools the sol changes into gel which
resembles a solid than liquid.
Both protein and starch can be used for forming gel.

21. • When a jelly is made, gelatin is
dispersed into a liquid and heated to
form a sol.As the sol cools, protein
molecules unwind forming a network
that traps water and forms a gel.
• If cornflour is mixed with water and
heated, the starch granules absorb
water until they rupture ,the starch then
disperses in water and the mixture
becomes more viscous and forms a gel
on cooling

22. S.No Sol Gel
1 The liquid state of a colloidal solution is called sol The solid or semi solid (Jelly like)
stage of a colloidal solution is
called gel
2 The sol does not have a definite structure Possess honeycomb like structure
3 The dispersion medium of the sol may be water or alcohol; Dispersion medium will be
hydrated colloid particles
4 The sol can be converted into gel by cooling Gel can be converted into sol by
heating
5 The sol can be easily dehydrated Gel cannot be dehydrated
6 The viscosity of the sol is very low Viscosity of gel is very high
7 Sol is categorized into lyophobic and lyophilic No such classification of gel
8 Example: Blood Example: Fruit jelly, cooked
gelatin

23. Other types of gel are formed with pectin and agar
• Pectin,a form of carbohydrate found in fruits in
production of jam until it is set. However ,for it to gel
there must be at least 50 per cent sugar and conditions
should be acidic.
• Agar is a polysaccharide extracted from seaweed which
is capable of forming gels.
• If a gel is allowed to stand for a time, it starts to ‘weep’
• This loss of liquid is known as syneresis.
Other types of gel

24. Emulsions:
A solution of one liquid with another immiscible liquid
When water and oil are shaken together, they form an
emulsion. If it is left to stand oil will separate at the top
of water. This is an unstable emulsion.Stable emulsion is
formed when two immiscible liquids are held stable by a
third substance.(Emulsifying agent)

25. Food emulsions:
• A food emulsion is basically a two-phase system consisting of a liquid,
such as oil, wax or essential oil and water.
• Most of the dispersed droplets in food emulsions are between 0.1 and 10
micrometers.
Food
emulsions
Oil in water
emulsions
Water in oil
emulsions

27. Emulsifiers
Emulsifiers are the substances which
reduce surface tension at the interface of
two normally immiscible phases,allowing
them to mix and form emulsion
They belong to the general class of
compounds called surface active agents
Functions of emulsifiers:
 To promote emulsion stability
 Control agglomeration of fat globules
 Modify texture
 Shelf life improved
 Modify rheological properties
 Control polymorphism and improve texture of
fats

28.  An emulsifying agent is made up of two parts:
One is hydrophilic(water loving) and other is hydrophobic(water hating).
 The emulsifier holds the disperse phase within the continuous phase.
This results in emulsion becoming stable

29. How do they work???
• Emulsifiers reduce surface tension between the two
immiscible phases due to their molecular structure
• They have both a polar group with affinity for water and
non polar group with affinity for oil

30.  Mayonnaise is an example of a
stable emulsion of oil and
vinegar, when egg yolk(lecithin
) may be used as an emulsifying
agent.
 Stability of emulsions
• Stabilizers are often added to
emulsions to increase the
viscosity of the product.
• These help to improve stability
of the emulsions, as over time
emulsions may separate.
• Stabilizers also increase shelf
life,E461 methylcellulose, used
in low fat spreads.

31. The particles in suspensions are larger
than those found in solutions.
Components of a suspension can be
evenly distributed by a mechanical
means, like by shaking the contents, but
the components will settle out.
Example: Oil andWater
Suspensions

32. Solutions Suspensions Colloids
Appearance
Clear, transparent and
homogeneous
Cloudy, heterogeneous, at
least two substances visible
Cloudy but uniform and
homogeneous
Particle Size molecule in size larger than 10,000 Angstroms 10-1000 Angstroms
Effect of Light (Tyndall Effect)
none -- light passes through,
particles do not reflect light
variable
light is dispersed by colloidal
particles
Effect of Sedimentation none
particles will eventually
settle out
none

33. Foams
• Foam is a two phase system in which the gas(air)
phase is dispersed in a small amount of
liquid(water) continuous phase
• Foam is desirable in beer, whipped egg white,ice
cream,marshmellow etc.
• The gas bubbles are separated from each other by
liquid walls that are elastic
• They have large amount of entrapped gases

34. Bubbly foam
• A bubbly foam is formed when the amount of gas
incorporated is low enough to retain roughly spherical
shape
Polyhedral foam
• The gas to liquid ratio is so large that bubbles are
pressed against one another in honeycomb like structure

35. Foam
formation
• Air has injected into
liquid
• Large air bubbles have
broken down into
bubbles
• Smaller bubbles have
be prevented from
during the formation of
foam

36. Foam stability
Foam becomes unstable due
drainage of water from their
structure. Foam stability is
desirable and can be
by
• Increasing elasticity of
wall
• Increasing viscosity of the
solution
• Adding polar foam

37. Antifoaming agents:
 In food industries undesirable foams may be formed
 Excessive formation leads to the loss of quality of the
product especially in fermentation processes.
 Antifoaming agents cause the collapse of foam and
retard the formation of additional foam.
 Eg. Silicon oils

38. Thank you