- What is dewaxing in edible oil refining?
- Where do waxes in edible oil come from?
- Dewaxing vs winterization
- How the dewaxing process works in 5 steps
- Where dewaxing sits in the refining line
- Filtration methods for dewaxing
- Process parameters that decide the result
- Common dewaxing problems and how to fix them
- How dewaxed oil is tested
- Planning a dewaxing line
- Frequently asked questions
Dewaxing in edible oil refining is the step that removes natural waxes from oils such as sunflower, rice bran and corn oil. These waxes stay dissolved while the oil is warm, then crystallise when it cools and leave a haze or sediment in the bottle. Dewaxing cools the oil under control, grows the wax into filterable crystals and separates them before the oil is packed.
This guide explains where edible oil waxes come from, how the dewaxing process works step by step, which parameters decide the result, and how the filtration stage affects oil yield and clarity.
Key takeaways
- Dewaxing in edible oil refining removes wax esters that make the oil cloudy at low temperature.
- The dewaxing process has five stages: conditioning, controlled cooling, crystal maturation, filtration and quality check.
- Cooling rate and holding time decide crystal size, and crystal size decides filtration speed.
- Low-shear filtration keeps wax crystals intact and reduces the oil lost in the wax cake.
What is dewaxing in edible oil refining?
Dewaxing in edible oil refining is a fractional crystallisation step. The oil is cooled until its wax components come out of solution as solid crystals, and those crystals are then removed by filtration. The treated oil stays clear during storage, retail display and refrigeration.
Dewaxing is usually applied to oils that are sold as clear liquid oils and carry a meaningful amount of wax: mainly sunflower, rice bran, corn and safflower oil, and some sesame and canola oils.
The quality target is expressed as a cold test: the oil must remain clear for a set time at 0 °C. Refiners and buyers agree the required clear time in the product specification.
Where do waxes in edible oil come from?
Plant waxes are esters of long-chain fatty acids and long-chain fatty alcohols. They form a protective layer on seed hulls and bran and move into the crude oil during pressing and solvent extraction. Because the molecules are long and saturated, they have high melting points (typically around 70–80 °C) and very low solubility in cold oil.
| Oil | Typical wax in crude oil | Main cold-stability step |
|---|---|---|
| Sunflower | Approx. 200–3,000 ppm, higher with more hull | Dewaxing |
| Rice bran | Approx. 1–4% | Dewaxing |
| Corn | Approx. 500 ppm, varies with germ and fibre | Dewaxing |
| Safflower | Low to moderate | Dewaxing |
| Cottonseed | Low wax, high-melting triglycerides | Winterization |
Dewaxing vs winterization
Both processes cool the oil and filter out solids, and many plants use the same cooling and filtration equipment for both. The difference is what is removed. Dewaxing removes wax esters present in small amounts. Winterization removes high-melting triglycerides (stearin), for example in cottonseed oil, which form a much larger solid fraction.
| Dewaxing | Winterization | |
|---|---|---|
| Material removed | Wax esters | Saturated triglycerides (stearin) |
| Typical oils | Sunflower, rice bran, corn | Cottonseed, some blends |
| Solid fraction | Small | Larger |
| Crystal behaviour | Fine, slow-growing crystals | Larger, faster-growing crystals |
| Filtration load | Low solids volume, fine crystals | High solids volume |
How the dewaxing process works in 5 steps
In practice, dewaxing in edible oil refining is a controlled temperature programme followed by a separation step. Each stage prepares the oil for the next one.
Step 1: Conditioning the oil
The oil is heated to around 55–65 °C so that any existing wax crystals dissolve completely. Starting from fully liquid oil gives uniform crystallisation in the next stage.
Step 2: Controlled cooling
The oil is cooled gradually to its crystallisation temperature, often in the range of 8–15 °C for sunflower oil. Cooling is done in stages, with chilled water in the final stage. Cooling too fast creates many very small crystals that blind the filter.
Step 3: Crystal maturation
The oil is held in maturation tanks with slow agitation for several hours, commonly 6–24 hours depending on oil type and wax content. Crystals grow and agglomerate to a size that can be filtered. Agitation must stay gentle, because high shear breaks crystals.
Step 4: Filtration
The matured oil is filtered at the crystallisation temperature. A filter aid such as perlite or cellulose may be dosed to build a porous cake. If the oil warms before filtration, wax re-dissolves and passes into the product.
Step 5: Polishing and quality check
A polishing filter removes remaining fines. The oil is then cold-tested before storage, deodorisation or packing.
Where dewaxing sits in the refining line
Plants position dewaxing in edible oil refining according to oil type and refining route:
- After bleaching, before deodorisation – a common position in both physical and chemical refining.
- Combined with neutralisation – sometimes called wet dewaxing, where wax is removed with the soapstock during centrifugation.
- After deodorisation – dewaxing as the final step, so no reheating takes place afterwards.
Rice bran oil is often dewaxed earlier in the line, because its high wax content interferes with degumming and bleaching.
Filtration methods for dewaxing
The filtration stage decides how much oil stays in the wax cake, how clear the product is and how much labour each cycle needs. Three filter types are common for dewaxing in edible oil refining:
| Method | How it works | Points to consider |
|---|---|---|
| Filter press (plate and frame / PP) | Oil is pumped through cloth-covered plates under pressure | Manual cake discharge; pumping pressure can break crystals; oil retained in cake |
| Pressure leaf filter | Vertical leaves in a closed pressure vessel | Closed operation; needs precoat of filter aid; pump shear on crystals |
| Gravity filter | Oil flows through the filter media under its own head at low pressure | Low shear keeps crystals intact; automatic cycle; needs enough filtration area for the capacity |
Eco Plus Filters builds automatic gravity filters for edible oil dewaxing and winterization. See the Eco Plus Gravity Filter for configuration and capacity details.
Process parameters that decide the result
- Cooling rate – slower cooling gives fewer, larger crystals.
- Crystallisation temperature – a lower temperature removes more wax but raises viscosity and filtration time.
- Maturation time – too short leaves fine crystals; too long adds tank volume.
- Agitation – enough for uniform heat transfer, not enough to break crystals.
- Filtration temperature – hold the oil at or slightly below the crystallisation temperature.
- Filter aid dose – improves cake permeability but adds cost and disposal volume.
- Residual soap, moisture and phospholipids – change crystal habit and slow filtration.
Common dewaxing problems and how to fix them
Oil turns cloudy after packing
Wax has passed the filter or crystallised later. Check filtration temperature, maturation time and filter integrity, and cold-test every batch before packing.
Slow filtration or frequent cleaning
Crystals are too fine. Reduce the cooling rate, check agitator speed and look for high-shear points such as pumps and valves between maturation and filtration.
High oil loss in the wax cake
The cake is holding oil. Improve cake drainage or blowing, and review whether a lower-shear filter would produce a firmer, more permeable cake.
Oil fails the cold test after deodorisation
Remaining wax has re-crystallised after reheating. Review where dewaxing sits in the line and consider a final dewaxing or polishing step.
How dewaxed oil is tested
The standard quality check for dewaxing in edible oil refining is the cold test. In AOCS Official Method Cc 11-53, a dried, filtered oil sample is sealed and held in an ice bath at 0 °C, and the result is the time the oil stays clear. The method’s basic pass mark is 5.5 hours; sunflower oil specifications often ask for longer clear times. Plants may also track haze and residual wax content.
Planning a dewaxing line
Results in dewaxing in edible oil refining come from the whole sequence: conditioning, cooling, maturation and a filtration stage that separates crystals without breaking them. When you plan a new line or replace a filter press, start with your oil type, capacity, wax content and available cycle window.
Planning a dewaxing or winterization line?
Send your oil type, plant capacity and current filtration method. A filtration engineer will reply with a first technical view.
Frequently asked questions
What is the purpose of dewaxing edible oil?
Dewaxing in edible oil refining removes natural waxes so that the oil stays clear at low temperatures and passes the cold test agreed in the product specification.
Which oils need dewaxing?
Sunflower, rice bran, corn and safflower oil are the most common. Some sesame and canola oils are also dewaxed.
What temperature is used for dewaxing?
Oil is typically heated to about 55–65 °C to dissolve existing crystals, then cooled slowly to about 8–15 °C and held for crystallisation. Exact values depend on oil type and wax content.
What is the difference between dewaxing and winterization?
Dewaxing removes wax esters present in small amounts. Winterization removes high-melting triglycerides (stearin), which form a larger solid fraction.
How long does the dewaxing process take?
Cooling and maturation usually take several hours up to a day, followed by filtration. Total time depends on oil type, wax content and plant design.
Which filter is best for dewaxing?
A filter that separates crystals at crystallisation temperature without breaking them. Gravity filters work at low pressure and low shear; filter presses and pressure leaf filters are also used.