mass transfer apllication in food industry

1. ADVANCE IN MASS TRANSFER
IN FOOD APPLICATION
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Prasented by
Swapnil Prashant Gautam
15/PFT/007
M.Tech (food tech)
First Year

2. DIFINITION
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 Mass transfer is the net movement of mass from one
location, usually meaning stream, phase, fraction or component, to
another.
 Mass transfer occurs in many processes, such as
absorption,evaporation,adsorption,drying,precipitation,membrane
filtration,and distillation. Mass transfer is used by different scientific disciplines
for different processes and mechanisms.
 The phrase is commonly used in engineering for
physical processes that
involve diffusive and convective transport of chemical
species within physical systems.

3. EXAMPLE
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 Some common examples of mass transfer processes are
the evaporation of water from a pond to the atmosphere, the
purification of blood in the kidneys and liver, and the distillation
of alcohol.
 In industrial processes, mass transfer operations include
separation of chemical components in distillation columns,
absorbers such as scrubbers, adsorbers such as activated
carbon beds, and liquid-liquid extraction.
 Mass transfer is often coupled to additional transport
processes, for instance in industrial cooling towers. These
towers couple heat transfer to mass transfer by allowing hot
water to flow in contact with hotter air and evaporate as it
absorbs heat from the air.

4. FUNDAMENTAL OF MASS
TRANSFER
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 A group of unit operations for separating the components of
mixtures is based on the transfer of material from one
homogenous phase to another.
 The driving force for transfer is a concentration difference or
a concentration gradient; much like a temperature difference or
a temperature gradient provides the driving force for heat
transfer.
 These methods, covered by the term mass-transfer
operations,
include such techniques as indicated below:
• Distillation
• Gas absorption
• Dehumidification
• Liquid extraction
• Leaching

5. Distillation
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 The purpose of distillation is to separate, by vaporization, a
liquid mixture of miscible and volatile substances into
individual components or, in some cases, into groups of
components.
 The separation of a mixture of alcohol and water into its
components; of air into nitrogen, oxygen, and argon; and of
crude
petroleum into gasoline, kerosene, fuel oil, and lubricating
stock are examples of
distillation

6. continue
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7. distillation has many applications
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In the fossil fuel industry distillation is a major class of operation in
obtaining materials from crude oilfor fuels and for chemical feedstocks.
Distillation permits separation of air into its components —
notably oxygen, nitrogen, and argon — for industrial use.
In the field of industrial chemistry, large ranges of crude liquid products
of chemical synthesis are distilled to separate them, either from other
products, or from impurities, or from unreacted starting materials.
Distillation of fermented products produces distilled beverages with a high
alcohol content, or separates out other fermentation products of commercial
value.

8. GAS ABSORPTION
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Gas absorption (also known as scrubbing) is an operation in
which a gas mixture is contacted with a liquid for the purpose of
preferentially dissolving one or more components of
the gas mixture and to provide a solution of them in the liquid.

9. continue
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The principal requirements of a tower packing are
 It must be chemically inert to the fluids in the tower.
 It must be strong without excessive weight.
 It must contain adequate passages for both streams without excessive
liquid holdup or pressure drop.
 It must provide good contact between liquid and gas.
 It must be reasonable in cost.

10. Dehumidification
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The process in which the moisture or water vapor or the
humidity is removed from the air keeping its dry bulb (DB)
temperature constant is called as the dehumidification
process. This process is represented by a straight vertical
line on the psychrometric chart starting from
the initial value of relative humidity, extending downwards
and ending at the final value of the relative humidity.
Dehumidification process along with cooling or
heating is used in number of air conditioning
applications. Let us see how these processes are
obtained and how they are represented on the
psychrometric chart

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12. Liquid extraction
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Liquid–liquid extraction also known as
solvent extraction and partitioning, is a method to separate
compounds based on their relative solubilities in two different
immiscible liquids, usually water and an organic solvent. It is
an extraction of a substance from one liquid into
another liquidphase.

13. Leaching
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Leaching normally refers to the removal of a substance from a solid via a
liquid extraction media. The desired component diffuses into the solvent
from its natural solid form. Examples of leaching include the removal of
sugar from sugar beets with hot water and the removal of nickel salts or
gold from their natural solid beds with sulfuric acid solutions.
Application:
It is used for leaching of gold from its ore by using sodium cyanide
solutions.
It is used for extraction of oil from oilseeds such as soyabeans by using
hexane or petroleum ether as a solvent.
It is used for extraction of sugar from sugar beats using hot water.
It is used for extraction of tannin from tree barks using water.
It is used for extraction of medicinal compounds from plant roots, leaves
and stems.
It is used for extraction of perfumes from flowers.
It is also used for preparation of tea and coffee.

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Drying
Drying is a mass transfer process consisting of the removal of water or
another solvent by evaporation from a solid, semi-solid or liquid. This process
is often used as a final production step before selling or packaging products
Applications of drying:
Food source:
Foods are dried to inhibit microbial development and quality decay.
However, the extent of drying depends on product end-use. Cereals and
oilseeds are dried after harvest to the moisture content that allows microbial
stability during storage. Vegetables are blanched before drying to avoid
rapid darkening, and drying is not only carried out to inhibit microbial growth,
but also to avoid browning during storage
Non food source:
Among non-food products, those that require considerable drying
are wood (as part of Timber processing), paper, flax, and washing powder.
The first two, owing to their organic origins, may develop mold if
insufficiently dried. Another benefit of drying is a reduction in volume and
weight.

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