Basic introduction of equipments used in dairy industry
Presentation on basic introduction
of equipments used in dairy
By:- AMRITA RANA(2113920)
DOON VALLEY INSTITUTE OF ENGINEERING AND TECHNOLOGY, KARNAL
•Dairy technology is a part of food engineering which deals with the processing of milk & its
•It is one of the main part of F.E which provides so many products with good nutritive value
•E.g. cheese, paneer, yogurt, curd, milk (varieties), khoya, lassi, ice-cream, butter, ghee, milk
powder, cream etc
•Indian diary technology has made a rapid progress with 2nd position of milk production
•As there are so many products which are made by milk, thus different equipments are
used for processing of milk and formation of different milk products.
Equipments Mainly used
* A homogenizer is a machine that takes a substance and makes it a uniform
consistency and helps reduce separation.
*It reduces the big fat globules into smaller one.
*Provides uniform consistency and give a smooth, rich flavor.
*One of the oldest applications of homogenizer is in milk processing.
*Homogenizer mainly works by agitating the liquid that is to be homogenized
Types of homogenizers
• Single stage homogenizer
• Two stage homogenizer
Difference between single stage and two
Pressure used= 2500psi
Mean size= 0.5um
Range = 0.2 to 2um
Clustering takes place
1. 1st stage= 2000psi
2. 2nd stage=500psi
No clustering takes place
More efficient than 1st stage
Commonly used in industrial scale
A pasteurizer is a device which pasteurizes, treating a food product to kill
disease-causing organisms such as bacteria.
Milk is one of the most widely pasteurized foods, but pasteurizers can also be
used with a variety of other liquids, and some other foods can be pasteurized as
Pasteurization is used to make food safer, so that it can be sold commercially
without concerns that people will get sick when they consume it.
People can also pasteurize foods at home when processing foods they have
•Batch (or "vat") pasteurization is the simplest and oldest method for
pasteurizing milk. Milk is heated to 63 degrees Celsius in a large
container and held at that temperature for 30 minutes.
•This process can be carried out at home on the stovetop using a
large pot or, for small-scale dairies, with steam-heated kettles and
fancy temperature control equipment.
•In batch processing, the milk has to be stirred constantly to make
sure that each particle of milk is heated
Continuous processing, a high temperature short time (HTST) pasteurizer is used. The milk is
heated to a temperature of 72 C and held for 15 seconds and then cooled rapidly. The heat
treatment is accomplished using a plate heat exchanger.
or flash pasteurization, is the most common method
these days, especially for higher volume processing.
This method is faster and more energy efficient than
An evaporator is a device used to turn the liquid form of a chemical into its
gaseous form. The liquid is evaporated, or vaporized, into a gas.
Evaporation is an important unit operation commonly employed to remove
water from dilute liquid foods to obtain concentrated liquid products.
Removal of water from foods provides microbiological stability and assists in
reducing transportation and storage cost
Concentration of milk to produce condensed milk
The manufacture of tomato paste, usually around 35-37% total solids, obtained by evaporating
water from tomato juice, which has an initial conc. Of 5-6% total solids.
Steam in (Saturated vapor)
Condensate out (Saturated
Vaccum for non condensable
The basic factors that affect the rate of
evaporation are the:
• rate at which heat can be transferred to the liquid,
• quantity of heat required to evaporate each kg of water,
• maximum allowable temperature of the liquid,
• pressure at which the evaporation takes place,
• changes that may occur in the foodstuff during the course of the evaporation process.
Types of Evaporators
1. Open kettle or pan
2. Horizontal-tube natural circulation evaporator
3. Vertical-type natural circulation evaporator
4. Long-tube vertical-type evaporator
5. Falling-film-type evaporator
6. Forced-circulation-type evaporator
7. Agitated-film evaporator
8. Open-pan solar evaporator
FIGURE 8.2-1. Different types of evaporators: (a) horizontal-tube type,
(b) vertical-tube type,
FIGURE 8.2-1. Different types of evaporators: (c) long-tube vertical type, (d)
•The feed enters at TF
•Saturated steam at TS enters the heat- exchange section.
•Condensed steam leaves as condensate or drips.
•The solution in the evaporator is assumed to be completely mixed
•Hence, the concentrated product and the solution in the evaporator have the
•Temperature T1 is the boiling point of the solution.
•The temperature of the vapor is also T1, since it is in equilibrium with the boiling
•The pressure is P1, which is the vapor pressure of the solution at T1.
If the solution to be evaporated is assumed to be dilute and like water, then 1 kg of steam
condensing will evaporate approximately 1 kg of vapor (if the feed entering has TF near the
The concept of an overall heat-transfer coefficient is used in the calculation of the rate of
heat transfer in an evaporator
The general equation can be written as:
q is the rate of heat transfer in W (btu/h),
U is the overall heat-transfer coefficient in W/m2. K (btu/h ft. °F),
A is the heat-transfer area in m2 (ft2),
TS is the temperature of the condensing steam in K (°F),
T1 is the boiling point of the liquid in K (°F).
Single-effect evaporators are often used when the required capacity of operation is relatively
small and/or the cost of steam is relatively cheap compared to the evaporator cost.
However, for large-capacity operation, using more than one effect will markedly reduce
Multiple effect evaporator
•A multiple-effect evaporator, as defined in chemical engineering, is an apparatus for efficiently using the heat
from steam to evaporate water.
• In a multiple-effect evaporator, water is boiled in a sequence of vessels, each held at a lower pressure than the
• Because the boiling temperature of water decreases as pressure decreases, the vapor boiled off in one vessel
can be used to heat the next, and only the first vessel (at the highest pressure) requires an external source of
• Originally designed for concentrating sugar in sugar cane juice, it has since become widely used in all industrial
applications where large volumes of water must be evaporated, such as salt production and water desalination
2. Forward-feed multiple-effect evaporators:
•A single-effect evaporator is wasteful of energy.
•The latent heat of the vapor leaving is not used but is discarded.
•Much of this latent heat, however, can be recovered and reused by employing a
multiple - effect evaporator.
•A simplified diagram of a forward-feed triple-effect evaporation system
FIGURE 8.2-3. Simplified diagram of forward -feed triple-effect evaporator.
•If the feed to the first effect is near the boiling point at the pressure in the first effect, 1kg of steam will
evaporate almost 1 kg of water.
•The first effect operates at a temperature that is high enough that the evaporated water serves as the
heating medium to the second effect.
•Here, again, almost another kg of water is evaporated, which can then be used as the heating medium to the
•As a very rough approximation, almost 3 kg of water will be evaporated for 1 kg of steam in a three-effect
•Hence, the steam economy, which is kg vapor evaporated/kg steam used, is increased.
•This also holds approximately for more than three effects.
•However, the increased steam economy of a multiple-effect evaporator is gained at the expense of the
original first cost of these evaporators. In forward-feed operation as shown in Fig. 8.2-3, the fresh feed is
added to the first effect and flows to the next in the same direction as the vapor flow.
•This method of operation is used when the feed is hot or when the final concentrated product might be
damaged at high temperatures.
•The boiling temperatures decrease from effect to effect. This means that if the first effect is at P1 = 1 atm abs
pressure, the last effect will be under vacuum at a pressure P3.
3. Backward-feed multiple-effect evaporators:
In the backward-feed operation shown in Fig. 8.2-4 for a triple-effect evaporator, the fresh feed enters
the last and coldest effect and continues on until the concentrated product leaves the first effect.
FIGURE 8.2-4. Simplified diagram at backward-feed triple-effect evaporator.
•This method of reverse feed is advantageous when the fresh feed is cold, since a
smaller amount of liquid must be heated to the higher temperatures in the second and
•However, liquid pumps must be used in each effect, since the flow is from low to high
•This reverse-feed method is also used when the concentrated product is highly
•The high temperatures in the early effects reduce the viscosity and give reasonable
4. Parallel-feed multiple-effect evaporators:
• Parallel-feed in multiple-effect evaporators involves the adding of fresh feed and withdrawal
of concentrated product from each effect.
•The vapor from each effect is still used to heat the next effect.
•This method of operation is mainly used when the feed is almost saturated and solid crystals
are the product, as in the evaporation of brine to make salt.
Uses of evaporators
•An evaporator is used in an air-conditioning system to allow a compressed cooling chemical
• It can also be used to remove water or other liquids from mixtures. The process of evaporation is widely used to
concentrate foods and chemicals as well as salvage solvents. In the concentration process, the goal of evaporation is
to vaporize most of the water from a solution which contains the desired product. In the case of desalination of sea
water or in Zero Liquid Discharge plants, the reverse purpose applies; evaporation removes the desirable drinking
water from the undesired product, salt.
•One of the most important applications of evaporation is in the food and beverage industry. Foods or beverages
that need to last for a considerable amount of time or need to have certain consistency, like coffee, go through an
evaporation step during processing.
•In the pharmaceutical industry, the evaporation process is used to eliminate excess moisture, providing an easily
handled product and improving product stability. Preservation of long-term activity or stabilization of enzymes in
laboratories are greatly assisted by the evaporation process.
•Another example of evaporation is in the recovery of sodium hydroxide in kraft pulping. Cutting down waste-
handling cost is another major reason for large companies to use evaporation applications. Legally, all producers of
waste must dispose of waste using methods compatible with environmental guidelines; these methods are costly.
By removing moisture through vaporization, industry can greatly reduce the amount of waste product that must be
The term drying refers generally to the removal of moisture from a substance. It is one of the oldest,
most commonly used and most energy consuming unit operation in the process industries.
Drying is often necessary in various industrial operations particularly in chemical process industries to
remove moisture from a wet solid, a solution or a gas to make it dry and choice of drying medium is
depends on the chemical nature of the materials.
Three basic methods of drying are used today
1) sun drying, a traditional method in which materials dry naturally in the sun,
2) hot air drying in which matrials are exposed to a blast of hot air and
3) freeze drying, in which frozen materials are placed in a vacuum chamber to draw out the water.
It is a method of producing a dry powder from a liquid or slurry by rapidly drying with a hot gas.
This is the preferred method of drying of many thermally-sensitive materials such as foods
It is a method used for drying out liquids from raw materials with drying drum. In the drum-
drying process, pureed raw ingredients are dried at relatively low temperatures over rotating,
high-capacity drums that produce sheets of drum-dried product. This product is milled to a
finished flake or powder form. Modern drum drying techniques results in dried ingredients
which reconstitute immediately and retain much of their original flavor, color and nutritional
Some advantages of drum drying include the ability of drum dryers to dry viscous foods which
cannot be easily dried with other methods. Drum dryers can be clean and hygienic and easy to
operate and maintain.
Other products where drum drying can be used are for example starches, breakfast
cereals, baby food, instant mashed potatoes to make them cold water soluble.
In fluid bed drying
heat is supplied by the fluidization gas, but the gas flow need not be the only source. Heat may
be effectively introduced by heating surfaces (panels or tubes) immersed in the fluidized layer.
•Those equipments which help in the freezing process so as to maintain the shelf life of a product
•Prevents the growth of mo’s
•Slow down the self decomposition of food products and enzymatic activity of product and
chemical changes within the product.
A batch freezer
It is a piece of equipment used in the commercial production of ice cream and frozen desserts,
like gelato and sorbet. As the name suggests, this freezer makes frozen desserts in batches that
can vary in size, with the size of each being controllable by the operator. Many small ice cream
stores and gourmet shops make their ice cream in this way:
Definite quantity of the mix is frozen at a time
Continuous freezing, which uses a steady flow of mix,
The principle of operation is very similar to that of a batch freezer, except that the freezing is
done under pressure(which increases the heat transfer rate) and the air is forced in or drawn
into the freezing chamber continuously at a metered rate.