Put a bottle of canola oil in the fridge. A few hours later, take it out – it’s cloudy, with a layer of flocculent material at the bottom.
Many consumers think the oil has gone bad. It hasn’t. That’s wax.
Canola and sunflower oil still contain trace amounts of natural wax esters after refining. These waxes come from the seed hull or seed coat. They dissolve in the oil at room temperature but crystallise out in the cold, making the oil cloudy. For bottled retail oil, cloudiness is a “shelf-appeal problem” – supermarkets won’t stock it, and consumers won’t buy it.
A dewaxing (winterization) line is the dedicated equipment system that “drives out” the wax. It’s not optional – it’s a hard threshold for canola and sunflower oil to enter the cold-clear oil market.
Where Does the Wax Come From? – Differences in Wax Content Between the Two Oils
Wax is a long-chain fatty acid ester naturally synthesised by oilseeds during growth. It is concentrated in the seed hull and seed coat and inevitably enters the crude oil during pressing.
Wax content varies significantly between oil types. A study published in the International Journal of Industrial Chemistry used chromatography to compare wax content in crude oils from three oilseeds:
| Oil Type | Crude Oil Wax Content |
|---|---|
| Sunflower oil | 0.45% ± 0.13% |
| Cottonseed oil | 0.07% ± 0.01% |
| Canola oil | 0.03% ± 0.01% |
Sunflower oil contains 15 times more wax than canola oil. This difference directly determines the difficulty and focus of dewaxing for each oil. Sunflower crude oil typically contains 600–900 ppm wax, and oil pressed from un-dehulled seeds can reach 2,000 ppm. Canola crude oil contains about 100–200 ppm wax.
It’s worth noting that the sediment causing cloudiness in canola oil differs from that in sunflower oil. A study of canola oil sediments from Canada and Australia found that 83% of the saturated fatty acids in canola sediment contain 24 or more carbon atoms, compared with only 50% in sunflower oil sediment. This means canola wax components are longer-chain, have higher melting points, and exhibit more complex crystallisation behaviour.
The Dewaxing Process: Cooling → Crystallisation → Filtration
The core logic of dewaxing is simple: cool the oil, let the wax crystallise, then filter out the crystals. But in practice, every step matters.
Step 1: Controlled Cooling (Crystallisation)
The oil is slowly cooled in a crystallizer. The cooling rate is critical – cool too fast, and the wax forms fine crystals that are difficult to filter; cool too slowly, and the production cycle lengthens and energy consumption rises.
Canola oil dewaxing is typically carried out at around 5°C. The crystallisation temperature window for sunflower oil is adjusted according to the raw material wax content – oils with higher wax content require lower cooling temperatures.
Step 2: Crystal Growth (Holding)
The oil is held at the target temperature for several hours with slow agitation. This step allows the wax crystals to grow large and stable enough to be effectively retained during subsequent filtration. Process data from CPM Crown shows that after cooling to the target temperature, the oil needs to be stirred at that temperature for up to 12 hours to ensure complete crystal formation. Skipping or shortening the holding stage is one of the most common reasons for poor dewaxing results.
Step 3: Filtration
After the holding stage, the oil passes through filtration equipment to separate the wax crystals. Common filtration equipment includes:
- Plate-and-frame filter press: Lower investment, suitable for small to medium capacity, but higher labour requirement
- Vertical leaf filter: Suitable for modern high-throughput plants, with a high degree of automation
Filtration usually requires the addition of a filter aid. The filter aid forms a pre-coat on the filter cloth, preventing wax crystals from clogging the pores while improving filtration rate.
An Easily Overlooked Variable: The Choice of Filter Aid
Filter aid is a “consumable” in dewaxing, but its selection directly affects filtration efficiency and operating costs.
Traditional filter aids are mainly diatomaceous earth and perlite. In recent years, cellulose-based filter aids have been gaining attention. A 2024 industrial-scale study published in Foods (DOI: 10.3390/foods13182960) systematically monitored and optimised the use of a cellulose-based filter aid in sunflower oil dewaxing. The team tracked 57 filtration cycles, recording key parameters such as pressure differential, filtration flow rate, constant-pressure time, and filter aid dosage, and used artificial neural networks for process prediction and optimisation.
Optimised filtration conditions: pressure differential 3.3 bar, total filtration time 39 hours (of which 32 hours were under constant pressure), filtered oil output 322,503 kg, and separated wax 90.41 kg. The optimal pre-coat filter aid dosage was 80 kg, the optimal body-feed filter aid dosage was 375 kg, and the optimal concentration was 0.12% w/w.
The main advantage of cellulose-based filter aids is environmental friendliness – traditional diatomaceous earth filter cakes are costly to dispose of, while cellulose-based cakes can be more easily disposed of or valorised. The main disadvantage is higher cost, but after optimising dosage through neural networks, the overall cost can be effectively controlled.
Core Equipment Configuration of a Dewaxing Line
A complete dewaxing line typically includes the following core equipment:
| Equipment | Function | Key Parameters |
|---|---|---|
| Crystallizer | Controlled cooling and crystal growth | Jacketed cooling, slow agitation, temperature accuracy ±0.5°C |
| Chilled water system | Provides cooling medium | Chiller unit + chilled water storage tank |
| Filter aid dosing system | Precise metering of pre-coat and body-feed filter aid | Automatic metering, controllable concentration |
| Filtration equipment | Separates wax crystals | Plate-and-frame filter press or vertical leaf filter |
| Dewaxed oil storage tank | Temporary storage of dewaxed finished oil | Stainless steel, temperature-controlled storage |
Selection logic for filtration equipment: Plate-and-frame filter presses have lower initial investment but require more manual operation, suitable for small to medium capacities (e.g., 5–50 TPD). Vertical leaf filters offer a high degree of automation and large filtration area, suitable for continuous production above 100 TPD.
A dewaxing line with a capacity of 10–30 tonnes per day typically requires an equipment investment in the range of tens of thousands to over one hundred thousand US dollars. For a continuous dewaxing line above 100 TPD, investment can reach several hundred thousand US dollars.
After Dewaxing: Market Value of Cold-Clear Oil
The direct output of dewaxing is winterized oil – a finished oil that remains clear and transparent under refrigeration. The core markets for winterized canola and sunflower oil are:
Salad oil and mayonnaise. Winterized oil is the base oil for salad dressings, mayonnaise, and sauces, because these products are often stored refrigerated, and the oil phase must remain clear at low temperatures.
Bottled retail oil. Canola and sunflower oil on supermarket shelves need to be dewaxed to ensure no cloudiness under any storage condition.
Export markets. Many international markets have clear specifications for the cold-clear stability of edible oils. Winterized oil meets international standards such as ISO 834 and ISO/TS 23647, serving as a passport for export trade.
The market for high-oleic winterized canola oil is growing particularly fast. In 2024, the global market for high-oleic winterized canola oil was approximately $2.4 billion, and it is projected to reach $4.1 billion by 2033, with a CAGR of approximately 6.3%.
Frequently Asked Questions (FAQ)
Q1: Do both canola oil and sunflower oil need dewaxing?
Sunflower oil almost always needs dewaxing – its crude oil wax content is typically 600–900 ppm, and can reach 2,000 ppm. Canola oil has a lower wax content (about 100–200 ppm), but if the product is intended for bottled retail or refrigerated applications, dewaxing is also required to ensure low-temperature clarity. After dewaxing, canola oil wax content must be reduced to below 50 ppm to avoid visible cloudiness.
Q2: Are dewaxing and winterization the same thing?
In the industry, the two terms are often used interchangeably, but there is a subtle difference: dewaxing specifically refers to the step of removing wax crystals; winterization is broader and can cover a wider range of cold-clear treatments, including the removal of high-melting triglycerides. For canola and sunflower oil, the core operation is dewaxing.
Q3: What are the core cost drivers of a dewaxing line?
Three factors: cooling energy consumption (cooling the oil and maintaining low temperature for several hours is the largest ongoing operating cost), filtration equipment type (plate-and-frame filter presses have low investment but high labour; leaf filters have high investment but high automation), and filter aid consumption (an ongoing consumable cost related to oil quality and wax content).
Q4: How is dewaxing performance verified?
The industry-standard acceptance test is the cold test: place an oil sample at 0°C for 24 hours and observe whether cloudiness appears. For more demanding applications, a 72-hour cold test can be performed. Dewaxed oil should remain clear and transparent in the cold test.
Q5: Does dewaxing affect the nutritional value of the oil?
Dewaxing is a purely physical process with no chemical modification. It only removes waxes and high-melting components, with minimal impact on beneficial minor components such as tocopherols and phytosterols. However, temperature and time during filtration need to be controlled to avoid unnecessary oxidation.
Q6: Can KMEC provide a complete plant solution for a dewaxing line?
Yes. KMEC provides a full set of dewaxing equipment, from crystallizers, chilled water systems, filter aid dosing systems, plate-and-frame filter presses, to vertical leaf filters. We can provide customised configurations based on your oil type (canola or sunflower), capacity target (5–500 TPD), and product positioning (domestic or export).
Final Thoughts
Dewaxing may not be the most glamorous step in the refining process, but it determines whether your oil can “go on the shelf.” For canola and sunflower oil, a well-designed dewaxing line is the final critical step that turns “cloudy crude oil” into “clear commercial oil on the shelf.”
If you are planning a canola or sunflower oil refining line, or wish to add a dewaxing section to an existing line, please contact KMEC. Our engineers can provide a complete solution from process design to equipment configuration based on your raw material characteristics and target market.
Data sources: International Journal of Industrial Chemistry (2013), Foods (2024, MDPI, DOI: 10.3390/foods13182960), CPM Crown Oils & Fats Refining Guide, Alfa Laval Dewaxing Systems, Oil Mill Machinery, and peer-reviewed research literature.