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Spray Drying of Dairy Products: Process, Benefits, and Applications

Q: Which dairy products can we make on a spray dryer?

Spray drying is used across the dairy industry to produce skimmed milk powder (SMP), whole milk powder, whey protein powder, whey protein concentrate (WPC), milk-based infant formulas, cheese powder, powder cream mixes and dried caseinate preparations. The feed is typically a dairy liquid such as milk, whey or a cream-based solution, atomised into fine droplets and dried in hot air to a stable powder.

Q: Why concentrate the milk before it goes into the spray dryer?

Concentration is the first step of the spray drying sequence because it raises the solid content of the dairy liquid and reduces the amount of liquid that must be evaporated in the drying chamber. Since spray drying uses a lot of heat, removing water ahead of atomisation lowers the evaporation load on the dryer and supports an efficient single-operation drying step.

Q: How do I choose between a rotary atomiser and a pressure nozzle?

A rotary atomiser uses the centrifugal force of high-speed blades and produces uniform particle sizes. A pressure nozzle converts pressure energy into kinetic energy and is ideal for free-flowing powders. Two-fluid or pneumatic nozzles combine compressed air with the liquid feed for high-velocity drying, while ultrasonic atomisers use vibrating surfaces to produce ultra-fine droplets below 50 microns.

Q: What determines the properties of the finished milk powder?

Atomisation and droplet-air contact are decisive. Atomisation increases surface area for optimum evaporation and leads to a dried product with the desired characteristics. The way the spray contacts the hot air in the drying chamber influences droplet behaviour during the drying phase and directly affects the properties of the dried powder. Evaporation of over 95% of the water occurs within seconds.

Q: How is the powder separated and how are fines recovered?

In a dairy spray dryer, large particles fall out by gravity into the collection base while fines are captured using cyclone separators, electrostatic precipitators, and filter bags or scrubbers. In the simplest single pass system, atomised droplets are sprayed into hot air and the dried particles fall into a collection bin, with the drying air vented out safely.

Q: What safety risks should we design for around a dairy spray dryer?

Three risks need control. Asphyxiation, because the drying gases used in the process are considered risky for plant labour. Powder contact, since the powder is potent on inhalation and poses a risk to machine operators. And explosion control, because dust, gas and heat are all potential trigger points for personnel working around the setup, so prevention measures are a must.

By PMG Engineering · 2 Jun 2023

Overview

Spray drying is one of the most widely used processes in the dairy industry to manufacture milk powders and dried dairy ingredients. As milk is highly perishable, its conversion into powdered form significantly extends its shelf life while retaining its nutritional value.

This advanced food processing technique is integral to modern dairy plant operations and is a core focus area for food processing consultants and dairy engineering experts involved in food factory design.

Spray drying

Spray drying involves the atomization of a dairy liquid—such as milk, whey, or cream-based solutions—into fine droplets using an atomizer. These droplets are rapidly dried with hot air in a controlled environment, producing fine powder with desirable moisture content and stability.

It is commonly used by food technology consulting firms to create:

Skimmed milk powder (SMP)
Whole milk powder
Whey protein concentrate (WPC)
Infant milk formulas
Cheese powders
Caseinate preparations

Products which are manufactured using spray dryer

Varieties of dairy products are manufactured using spray dryer including; Skimmed milk powder (SMP), Whole milk powder, Whey protein powder, Whey protein concentrates (WPC), Milk-based infant foods, cheese powder, powder cream mixes and dried caseinate preparations.

General steps of spray drying:

(a) Concentration

Increase solid content

Reduce the amount of liquid that must be evaporated.

(b) Atomization

Inc. SA for optimum evaporation.

To leat to a dried prod. Having desired characteristics.

(c) Droplet air contact

Atomized liquid is brought in contact with the hot air in the drying chamber.

Rsults in evaporation of >95% water.

The way in which spray makes contact with the hot air influences the behavior of droplets in the drying phase and directly affects the properties of the dried product.

(d) Droplet drying

Fine droplets are introduced into a hot air chamber.

Evaporation of over 95% water occurs within seconds.

(e) Separation:

Large particles fall by gravity.

Fines are captured using:

Cyclone separators
Electrostatic precipitators
Filter bags or scrubbers

Single Pass System:

The simplest form.

Atomized droplets are sprayed into hot air.

Dried particles fall into a collection bin.

Basic flow system:

Product is pumped through a feed tank to an atomizer.

Drying gas is introduced simultaneously.

Powder is collected in the base while air is vented out safely.

Let’s discuss different types of Atomizers:-

(a) Rotary atomizer

Uses centrifugal force of high-speed blades.

Produces uniform particle sizes.

(b) Pressure nozzle

Converts pressure energy into kinetic energy.

Ideal for free-flowing powders.

(c) Two fluid or pneumatic nozzle

Combines compressed air with liquid feed.

Used for high-velocity drying.

(d) Ultrasonic atomizer

Uses vibrating surfaces.
Produces ultra-fine droplets (<50 microns).

Advantages of the spray drying process:

· Efficient drying process.

· Heat-sensitive and oxidizable materials.

· It can be designed for drying under sterile cond.

· Dried particle has uniform size and shape.

· Good flow property can be easily compressed.

· Used for coating and encapsulation of solids and liquids.

· Labour cost is low, drying in a single operation.

Disadvantages of the spray drying process:

. Solid materials can not be dried.

· Costly and bulky equipment.

· Cleaning is time-consuming.

· Uses lots of heat.

Safety protocols that need to be taken care:

Asphyxiation: Drying gases that are used in the drying process are considered risky, so preventing the factory labor from asphyxiation caused by gases is a must.

Powder contact: This process is considered potent on inhalation and can pose a risk to machine operators.

Explosion control- dust gas and heat are all potential trigger points, prevention is a must for the workers working around the setup.

Conclusion:

Spray drying is a vital technique in the processing and preservation of dairy products, transforming perishable liquids into shelf-stable, nutritious powders. It is an indispensable method for any modern dairy facility looking to scale production efficiently.

By optimizing spray drying through expert food processing consultancy, manufacturers can ensure product quality, regulatory compliance, and market competitiveness.

References:

Frequently asked

Which dairy products can we make on a spray dryer?

Spray drying is used across the dairy industry to produce skimmed milk powder (SMP), whole milk powder, whey protein powder, whey protein concentrate (WPC), milk-based infant formulas, cheese powder, powder cream mixes and dried caseinate preparations. The feed is typically a dairy liquid such as milk, whey or a cream-based solution, atomised into fine droplets and dried in hot air to a stable powder.

Why concentrate the milk before it goes into the spray dryer?

Concentration is the first step of the spray drying sequence because it raises the solid content of the dairy liquid and reduces the amount of liquid that must be evaporated in the drying chamber. Since spray drying uses a lot of heat, removing water ahead of atomisation lowers the evaporation load on the dryer and supports an efficient single-operation drying step.

How do I choose between a rotary atomiser and a pressure nozzle?

A rotary atomiser uses the centrifugal force of high-speed blades and produces uniform particle sizes. A pressure nozzle converts pressure energy into kinetic energy and is ideal for free-flowing powders. Two-fluid or pneumatic nozzles combine compressed air with the liquid feed for high-velocity drying, while ultrasonic atomisers use vibrating surfaces to produce ultra-fine droplets below 50 microns.

What determines the properties of the finished milk powder?

Atomisation and droplet-air contact are decisive. Atomisation increases surface area for optimum evaporation and leads to a dried product with the desired characteristics. The way the spray contacts the hot air in the drying chamber influences droplet behaviour during the drying phase and directly affects the properties of the dried powder. Evaporation of over 95% of the water occurs within seconds.

How is the powder separated and how are fines recovered?

In a dairy spray dryer, large particles fall out by gravity into the collection base while fines are captured using cyclone separators, electrostatic precipitators, and filter bags or scrubbers. In the simplest single pass system, atomised droplets are sprayed into hot air and the dried particles fall into a collection bin, with the drying air vented out safely.

What safety risks should we design for around a dairy spray dryer?

Three risks need control. Asphyxiation, because the drying gases used in the process are considered risky for plant labour. Powder contact, since the powder is potent on inhalation and poses a risk to machine operators. And explosion control, because dust, gas and heat are all potential trigger points for personnel working around the setup, so prevention measures are a must.

CITE THIS

PMG Engineering. (2023). Spray Drying of Dairy Products: Process, Benefits, and Applications. PMG Engineering. https://pmg.engineering/Article/189/spray-drying-of-dairy-products-process-benefits-and-applications/

https://pmg.engineering/Article/189/spray-drying-of-dairy-products-process-benefits-and-applications/