Spray Drying

What is a Spray Dryer?

A spray dryer is used to dry a product quickly. Spray driers are very effective; in a single step they can turn a solution into a dried powder. Dry powders are often easier to handle in production. This also allows ingredients that would otherwise be liquids to be incorporated into dry powder blends such as premixes. The resulting powders formed from the spray drying process are free flowing and easy to handle and scale.

A spray drier works by separating the solids from a liquid through evaporation. To do this a liquid is sprayed through a nozzle into a hot vapor stream. The solids form from the liquid as the moisture leaves the droplets. The solid is collected as it passes through the outlet.
 

What is Spray Drying Microencapsulation?

Spray drying for microencapsulation is very different then the fluidized bed processes.   In spray drying for encapsulation we change a liquid into a powder form. The process starts with an emulsion or dispersion.

Unlike the fluidized bed methods spray drying does not produce a full microencapsulation; we are not building a shell or matrix on the outside of the particle. Instead, in the spray drying process, we are creating a dispersion or emulsion of an ingredient within another ingredient and then drying this emulsion very quickly. On the outside edges of the resulting dry particles there will always be some of the active components or active ingredient. The inside core is much more protected. Examples for spray drying applications include the fat-soluble vitamins such as vitamin A, vitamin D, and vitamin E. When spray-dried, these vitamins are much more stable for shelf life, however, there will always be some amount of surface oil.

Key points of difference in the process of spray drying for encapsulation:

• Spray drying process turns liquids into powders
• Spray drying starts with an emulsion or dispersion
• Spray-dried materials are not fully encapsulated

Examples of spray drying for encapsulation:

• Fat-soluble vitamins
• Healthy lipids

Benefits of spray drying for encapsulation:

• Results in free-flowing powders
• Stabilized for shelf life

Beta Carotene

Innovation in Spray Drying Technology

In spray drying you can have huge functionality changes depending on how you make up the emulsions.

In the image above we took spray dried beta carotene made by three different methods. We dissolved each in water to simulate a beverage application. Each of the bottles above contain 25% of the DV (daily value) for vitamin A. Each was made from the same beta carotene starting material. But their appearance is very different.

Vitamin A’s most common forms are vitamin A acetate and vitamin A palmitate. The third most common is beta-carotene. Beta-carotene is great because people see it as a nature identical source of vitamin A. Your body only converts the amount of vitamin A you need from beta-carotene. Unlike other forms of vitamin A, it does not store in the liver. Instead, your body stores vitamin A in your skin cells. This makes beta-carotene a very safe way of delivering vitamin A without concerns for toxicity.

The problem with beta-carotene in many applications is its color. Similar to carrots, which are rich in beta-carotene, it is bright orange. The intense color can make it difficult to use in formulations of foods, beverages, and dietary supplements. Beta-carotene is also less stable than other forms of vitamin A.

Typical Emulsion

The image above is an illustration of a typical emulsion that might be spray dried. The particles would be in the 0.5 to 1-micron range. You have multiple particles that are encapsulated in one beadlet of the matrix. In this example, we are using beta carotene. If this emulsion was spray dried, the powder could be used in an application like an orange-colored beverage. In that application, the color impact would not be a problem.

What is a typical emulsion?

• Particle size range: 0.5 to 1 micron
• Multiple particles encapsulated into one matrix

When the resulting spray dried power from this emulsion was dissolved into water the result would be similar to the bottle on the far left. There would be a strong color and some cloudiness.
 

Micellar Dispersions

At Glanbia, we can change the emulsion system so that, in turn, it changes the appearance of the finished product. In the illustration above, we are showing a micellular dispersion. A micellular dispersion is a single particle delivered in a larger matrix.

What is a typical micellular dispersion?

• Particle size range: 50 to 100 nm
• Single-particle in a larger matrix

The result is an optically clear solution with no cloudiness. If the spray-dried material were dissolved in water, the result would be similar to the bottle on the far right. You can see there is still color contribution, but the solution is much clearer.
 

Colloidal Dispersions

A good example of innovation in spray drying is our BetaClear™ beta-carotene.   The illustration above shows a colloidal dispersion. When spray-dried, this colloidal dispersion will result in a dramatically different appearance in the finished product. There will be significantly less color contribution.

The colloidal dispersion almost tricks the eye in a way because it is light scattering.

What is a typical colloidal dispersion?

• Single-particle
• Light scattering

In the picture of the three bottles, each contains 25% of the daily value (DV) for vitamin A.

If dissolved into solution the spray dried colloidal dispersion would be similar to the center bottle. The solution would be clear and there would be minimal color contribution.

Applications for BetaClear™ include beverages, powder blends, and tablets.

Spray Drying Process in the Food and Supplement Industries

A growing number of consumer products are being fortified to help deliver essential vitamins and minerals to the end-user. Companies must determine the optimal way to deliver the recommended daily allowance (RDA) for that nutrient.

Premixes are one of the ways that companies like Glanbia are able to deliver the nutrient profile a consumer desires. Since many functional food ingredients can compose a product, processing technology must be looked at as well.

Typically, blending is utilized to make a premix, but other alternatives—spray drying, agglomeration, encapsulation, and roll compaction—also exist and can be used to create a homogenous premix blend. The spray drying process takes a liquid slurry and, under a temperature differential, removes the moisture giving a dried powder.

Factors Affecting Spray Drying

Spray Drying Parameters

There are several spray drying parameters that must be considered when selecting the optimal method to produce your dry powder.

Determine product moisture and particle size requirement as these can impact atomizer choice. For example, an atomizer wheel will give you a wider distribution of particle size while a nozzle will give you narrower distribution.

Selecting the right atomizer can also impact your product color as particle size and color are intertwined. Furthermore, if a nozzle is chosen, whether the nozzle is being used as part of a co-current flow or counter-current flow is another variable to consider as residence time in the dryer and particle size of the powder are impacted.

Another factor is the order of addition. Order of addition of raw materials can impact the viability of the emulsion or solution to be spray dried. Slurry temperature can also impact the viscosity of the material to be pumped. These are just some of the basic variables to look at when evaluating spray drying as a means to produce your powder.