Spray dryer treatment of oil and grease technology in detail

Spray dryers are used to process oils and fats. Their main purpose is to convert liquid oils and fats (or emulsions containing oils and fats) into free-flowing powders. This solves many inconveniences in the storage, transportation and use of liquid oils and fats, and brings a series of technical advantages.

The core motivations and advantages of converting oils and fats into powders include:

Improving stability and extending shelf life

• Physical stability: The powder state eliminates the stratification and precipitation problems that may exist in liquid oils.
• Oxidative stability: This is one of the most critical reasons. Liquid oils and fats are very susceptible to oxidation and rancidity when exposed to air (oxygen), light and heat. Spray drying process:

1. Encapsulation: The oils and fats are encapsulated in a matrix formed by wall materials (such as modified starch, maltodextrin, colloids, proteins), forming a physical barrier that greatly reduces the direct contact of the oils and fats with oxygen, light and metal ions (pro-oxidants).

2. Reduce water activity: The drying process significantly reduces the water activity of the product, inhibiting microbial growth and certain oxidation reactions.

3. Antioxidants can be added: Antioxidants (such as TBHQ, BHA, BHT, tocopherol) can be easily added during the emulsification stage to evenly distribute them in the powder, further delaying oxidation.

Improved fluidity and ease of use

• Powdered fats have excellent fluidity and are easy to accurately add through automatic metering and mixing equipment, improving production efficiency and formula accuracy.
• It avoids the problems of liquid fats adhering, dripping, difficult to weigh, and difficult to mix evenly with other dry powder raw materials (such as flour, milk powder, and sugar powder).

Convenient storage and transportation

• Powders are smaller in volume and higher in density than liquids, which greatly saves storage and transportation space and reduces logistics costs.
• Powder form is less prone to leakage, and packaging and transportation are safer and cleaner.

Expand the scope of application

• Powdered fats can be easily added to various foods that require fats but require dry powder state, such as:

1. Instant drinks (coffee mate, creamer powder, cocoa powder)

2. Baking premix (cake powder, bread powder)

3. Soup powder, sauce powder

4. Ice cream powder, milk powder

5. Nutritional supplements, meal replacement powder

6. Candy, chocolate products

7. Meat processing (as functional fat powder)

• Powdered fat products with specific functional properties (such as different melting points, different emulsification) can be developed.

Improve dispersibility and solubility

After spray drying, when the powder of emulsified fat is rehydrated, the fat can be dispersed in water faster and more evenly to form a stable emulsion, which is crucial for instant products.

The process of converting liquid oil into powdered oil is a typical microencapsulation process, and the main steps are as follows:

Formula design and raw material preparation

• Oil: Select the oil that needs to be powdered (such as palm oil, soybean oil, coconut oil, milk fat, fish oil, etc.), which can be a single oil or a mixed oil.
• Wall material: Select a suitable wall material to encapsulate the oil. Common wall materials include:

1. Carbohydrates: modified starch (such as sodium starch octenyl succinate), maltodextrin, corn syrup solids, cyclodextrin, gum arabic.

2. Proteins: whey protein, sodium caseinate, soy protein isolate.

3. Colloids: guar gum, xanthan gum.

4. Usually a variety of wall materials are used to achieve the best emulsification, film-forming, embedding rate and solubility.

• Emulsifier: Add emulsifiers (such as monoglycerides, lecithin, sucrose esters, etc.) to help form smaller and more stable oil droplets.
• Antioxidants: Add as needed.
• Water: As a dispersion medium.

Emulsification

• Heat the oil to above the melting point (to keep it in liquid form).
• Dissolve or disperse the wall material, emulsifier, antioxidant, etc. in hot water to make the water phase.
• Slowly add the hot oil to the water phase under high-speed shear stirring to form a coarse emulsion.
• This is the most critical step, the goal is to obtain the smallest possible oil droplets and disperse them evenly.

Homogenization

• The coarse emulsion is homogenized by a high-pressure homogenizer (usually 1-2 times at 10-50 MPa or even higher pressure).
• High-pressure homogenization further breaks the oil droplets into micron or even submicron levels (usually targeting 0.5-2 microns), forming an extremely fine, uniform and physically stable water-in-oil emulsion. Fine oil droplets are the key to obtaining a high embedding rate powder.

Spray drying

• Pump the homogenized stable emulsion into the atomizer at the top of the spray drying tower.
• Atomization: The emulsion is atomized into extremely fine droplets (tens to hundreds of microns). Commonly used atomizers are:

1. Rotary atomizer: High-speed rotating disk generates centrifugal force to throw the liquid into fine mist.

2. Pressure nozzle: High pressure forces the liquid to form mist through small holes.

3. Airflow nozzle: Use high-speed airflow to tear the liquid into droplets.

• Drying: Hot air (usually between 160-220°C at the inlet temperature, depending on the thermal sensitivity of the material) is introduced from the top or bottom of the drying tower and contacts the droplets in the same or countercurrent flow. The water in the droplets is evaporated in a very short time (several seconds to tens of seconds).
• Powder formation: After the water evaporates quickly, the wall material dissolved in the water quickly solidifies around the oil droplets to form one or more layers of continuous, porous wall film, which wraps the oil inside to form dry microcapsule particles (powdered oil).
• Cooling and collection: The dried powder falls to the bottom of the tower and is separated and collected from the exhaust gas by a cyclone separator or bag filter. The collected powder is still at a high temperature and needs to be cooled quickly (such as fluidized bed cooling) to prevent agglomeration and thermal damage.

Post-processing and packaging

• Screening: Oversized or agglomerated particles may be removed by vibrating screens to ensure powder fluidity.
• Anti-caking treatment: Sometimes a small amount of anti-caking agent (such as silica) is added to the powder surface.
• Packaging: In a low humidity environment (control moisture absorption), the powder is sealed and stored in moisture-proof and oxygen-proof packaging materials (such as aluminum foil composite bags).

• Emulsion stability: The stability of the emulsion before homogenization directly affects the quality and embedding rate of the final powder.
• Homogenization effect: The size and distribution of oil droplets are the core factors that determine the embedding efficiency.
• Solid content: The solid content of the emulsion (the total dry matter ratio of oil + wall material) affects the atomization effect, drying efficiency and the physical properties of the powder (density, fluidity). It is usually optimized between 30%-50%.
• Inlet air temperature and outlet air temperature: Inlet air temperature affects drying rate and thermal efficiency; outlet air temperature is a key indicator for controlling the moisture content of the final powder, which requires balancing drying efficiency and preventing the degradation of heat-sensitive components (oils, proteins). The outlet air temperature is usually controlled at around 80-100°C.
• Atomization effect: The droplet size affects the drying rate and the particle size and characteristics of the final powder particles.

Spray drying is the core technology for producing powdered oils. By carefully designing the formula (oils, wall materials, emulsifiers), preparing stable water-in-oil emulsions (the core is homogenization), and utilizing the rapid dehydration characteristics of spray drying, liquid oils that are easily oxidized and difficult to handle can be converted into stable, well-flowing, easy-to-use, long-shelf-life and widely used powder products. The core goal of the entire process is to achieve microencapsulation of oils to achieve the purpose of protection and functionalization.