Centrifugal and Mixing Flashcards
SEDIMENTATION
The separation of
i) two immiscible liquids or
ii) a liquid and a solid
depends on the effects of gravity/density on the
components.
Slow process
Application in food industry (Sendimentation)
separating dirt from incoming raw material, crystal from mother liquor, separate fat/cream from milk (original method)
CENTRIFUGAL SEPARATIONS
▪ Centrifugal force
- speed up the rate of sedimentation
▪ The particles are separated from the fluid by
centrifugal forces acting on particles of various sizes and densities
CENTRIFUGAL FORCE
▪ Centrifugal separators make use of the common
principle that an object whirled about an axis or center point at a constant radial distance from the point is acted on by a force.
▪ Centrifugal force acts on the particle to maintain it in the circular path
Application of liquid separation using centrifuge
In the dairy industry in which the emulsion, milk, is separated by a centrifuge into skim milk and
cream.
The milk is fed continuously into the machine,
i) Which is generally a bowl rotating about a vertical axis,
ii) Cream and skim milk come from the respective
discharges.
Clarification of Meat Broths and Stocks:
Process:
•Meat broths and stocks often contain fine particles of fat, protein, and bone.
•Centrifugation helps in separating these fine
particles, resulting in a clearer broth or stock.
Application:
•Used in the production of high-quality soups,
consommés, and sauces.
Fish Oil Extraction:
Process:
• During the processing of fish, the fish oil is extracted and then centrifuged to separate the oil from water and solid impurities.
Application:
• The refined fish oil is used in dietary supplements, animal feed, and various industrial applications.
Mixing
Unit operation in which a uniform mixture is obtained from two or more components by dispersing one within the others.
The primary objective :- A homogenous mixture
Used to combine ingredients to achieve different functional properties or sensory characteristics.
In some cases, mixing is required to promote some other objective such as mass & heat transfer or chemical reaction.
Food mixing involves ingredients of different physical properties and quantities
Mixing systems:
Gas/liquid - carbonated drinks
Liquid/liquid – full cream milk
Solid/liquid - batter
Solid/solid – sausage, nugget
Characteristics of Mixtures
A mixing process begins with the components, grouped together in some container, but still separate as pure components.
If small samples are taken throughout the container, almost all samples will consist of one pure component.
As mixing then proceeds, samples will increasingly contain more of the components.
Complete mixing - all samples are found to contain the components in the same proportions as in the whole mixture.
Types of mixture
1) Solutions (Salt Water)
2) Suspensions (Muddy Water)
3) Colloidal (Milk)
4) Emulsion (Mayonnaise)
5) Foams (Whipped Cream)
Mechanism of mixing:
1) Bulk Transport
2) Turbulent Mixing
3) Molecular Diffusion
Bulk transport
• Movement of a large portion of a material from
one location to another location in a given
system. Rotating blades and paddles are used.
Turbulent mixing
Due to turbulent flow, which results in random
fluctuation of the fluid velocity at any given point
Molecular diffusion
Molecular diffusion is explained by Ficks’s law,
which depends on the concentration gradient at
different regions
