The document describes emulsions as colloidal suspensions of one liquid in another immiscible liquid, highlighting oil-in-water (o/w) and water-in-oil (w/o) types with examples from food products. It outlines the formation and stability of emulsions, the role of emulsifiers, and factors affecting their properties, including droplet size, viscosity, and stabilizers. Additionally, it touches on foams as dispersions of gas in liquid, detailing their formation and stability, as well as instrumentation techniques like spectrophotometry used in analyzing chemical compositions.

1. MODULE8
EMULSION
Anemulsion is a colloidal suspension ofone liquid in another immiscible ( they will not mix together) liquid.
A10od
emulsion is basically a two phase systems consisting of aliquid such as oil, wax or essential oil and water.
Most of the dispersed droplets in food emulsions, have diameters between 0.1 of IOUm
There are two types of food emulsion :-oilinwater(o/w)andwaterinoil(W/o)
Oil in water emulsion consists of lipid dropletsdisporsed in water eg- milk, cream, ice cream, mayonnaise, salad dressings
water in Oil emulsion made up ofwaterdroplets dispersed in a continiuos oil phase. Eg:- butter, margarine (solid emulsion
Formation ofemulsion
The most common method ofprepearing an emulsion is by mechanically dispersing one liquid phase in another
Formation of small droplets take place froma beater blade or from passageofthecoarse emulsion through a homogenizer
A stable emulsion is not formed by a mere mixing ofthe liquids.
When the emulsion is left to stand, droplets in the dispersed phase coalesce due to surface tension
An emulsion added to the s,tem would reduce the interfacial tension, enhance the formation of small droplets and
reduce therateatwhich droplets coales.
Properties ofemulsion
Foodemulsion musthave appropriate appearance( colour and opacity ), texture (viscosity, plasticity, and oiliness) and
flavour for accepetance
Some features of food emulsions are ofimportance from the point of view offood quality. Oil in water emulsion helps the
incorporation of fect soluble flavouring and colouring matter or vitamins.
The opacity of a fluid product can be created by dispersing droplets of very small size(0.05-1.0 0) in the continuous
phase
A high degree of plasticity can be achieved by raising the concentration ofthe dispersed liquid to about 60 % or above.
T h e opacity of emulsion is detemined by droplet size , droplet concentration and difference in the refractive indices of the
two phases.
An emulsion is transparent when the refractive indices of the two liquids are the same or when the droplet diameter is
0.05Om or less. An increase in the size of the droplets results in opaqueness which reaches a maximum when the size is
0.05 to 1.00 0
The viscsiiy of the continuous phase is a major factor in governing the properties of an emulsion. In many food emulsions,
gums cre added to an emulsion
Gam stabilizes an emulsion by being adsorbed at the oll- water interface to form a hydrated filim and by increasing the
viscosity ofthe continuous phase
Stability ofemulsions

2. Stabilizers are often added to emulsions to increase the viscosity of the products.
These help to improve stability of theemulsions, as over the time emulsions may separate.
Emulsions can be stabilized by the use of emulsifiers, finely dividedparticles absorbed at the interface, an
dispersible hydrocolloids.
r
Emulsifiers
Emulsifiersare the substances which reduce surface tension at the interface of two normally immiscible phase, allov
them to mix and form emulsion. They belong to the general class of compounds called surface active agentis.
Functions
To promote emulsion stability
Control agglomeration of fat globules
Modify texture
Shelflife improved
Modify rhelogical properties
Control polymorphism and improve texture of fats
Structure ofemulsifiers
An emulsifying agent is made up oftwo parts- one is hydrophilic (water loving) and other is hydrophobic (water hating)
The emulsifier holds the dispersed phase within the continuous phase. This results in emulsion becoming stable.
There are both ionic and non-ionic compounds. Some ionic emulasifiers used are salts of fatty acids propylene glycol and
sorbitan
Action ofemulsifiers
Emulsion reduce surface tension between the two immiscible phase due to their molecular structure.
They have both a polar group with affinity for water and non-polar group with affinity for oil.
Mayonnaise is an eg ofstable emulsion ofoil and vinegar, when egg yolk (lecithin) may be used as an emulsifying agent
lonic emulsifiers can react with ions(H+ ions, inorganic ions, or oppositely charged emulsifier ions) to form complexs,
which may have reduce emulsifying power and low stability in both the liquids. In contrast, non-ionic emulsifiers are
generally soluble in one of the phases and donot react with ions. For this reason , non- ionic emulsifiers are extensively
uses in foods.
Stabilizers aiso increase shelf life.eg:-plant gums, gelatine, pectin, alginates, cellulose derivatives, such as carboxymethyl,
hydroxyl propyl and methyl cellulosegums.
Foams
Foams are two phase system in which the gas (air) phase is dispersed in a small amount of liquid (water) continuos phase
The gas bubbles arc separated frota each other by a liquid walls (fiims orcamellae) that are elastic.
The diameters of the foam bubbles range from about 1 Um to several centimetres
Depending on the bubble size and wall thickness, dense or light foams are formed.
Foams is desirable in beer, whipped egg white, ice cream, cake, bread, marshmellow etc.
They have large amount ofentrapped gases
Foam formation
For the formation of foam there must be a foaming agent in the continuous phase prior to dispersion ofgas. Foams are formed h
injecting gas into the foaming solution through orifices orby introducing gas while beating the solution. Theyare prepared
dissolving the gas under pressure in he solution that is to be foamed on release of pressure; since dissolved gas leavesandthe restof
ae gas in the systeri expands, foam is created.
Foam stability
Foam become unstable due to drainage ofwater from their structure, Foam stability can be enhanced by:-
Increasing elasticity of wall
Incr:asing viscosity cfthe solution
Adding polar foam stabilizers.
Viscosity ofthesolution can be increased by gums and proteins, such as getatin, SOmeume sugars are vsed in the foanm to inc
VIscosity as well as act as sweetening agents. ease

3. MODULE 9&10
INSTRUMENTATION, COLORIMETRY & SPECTROSCOPY
Spectroscopy deals with the study ofelectromagnetic radiation emitted or absorbed by agivenchemicalspecies.
Or Spectroscopy deals with the interaction ofelectromagnetic vacliationwithmatte
Spectrophotometer is an instrument that measures the amount of light absorbed by a substance n other words
spectrophotometer measure light absorption as a function ofwavelength in U as vell as visible regions and follows the
Beer-Lambert's lawof light absorption.
Spectrochemical analysis is widely used in analyticallaboratoriesfor thequantativeanalysisofthechemical composition
offoods.
Common spectrochemical analysis methods includeultraviolet,visibleand infraredabsorption spectroscopy, molecular
fluorescence spectroscopy and nuclear magneticresonancespectroscopy (NMRS)
In each of these method ,analyst attempts to measure the amount of radiation ejther
analyst(sample)
absorbed or emitted by the