Rice bran oil is often called “nutritional gold oil.” It is rich in gamma-oryzanol, phytosterols, and vitamin E, and contains up to 70% unsaturated fatty acids. The global rice bran oil market was valued at approximately $10.8 billion in 2025 and is projected to reach nearly $26.2 billion by 2034.
But between crude rice bran oil and crystal-clear finished oil lies a five-stage refining journey. Unlike other vegetable oils, rice bran oil refining faces two major challenges: high wax content (3%–12%) and high acidity (acid value can spike sharply within 6 hours of rice bran milling).
The make-or-break step in rice bran oil refining is not degumming and not bleaching – it is dewaxing. These five stages are interdependent and indispensable, but the most critical and unique step is dewaxing (winterisation). It is the dividing line that determines whether rice bran oil moves from “crude oil” to “commercial product.”
This article breaks down the five key stages of rice bran oil refining – degumming, dewaxing, bleaching, deacidification, and deodorisation – with a particular focus on why dewaxing is the defining factor for oil quality and market value.
From Rice Bran to Crude Oil: Pressing Is the Prerequisite to Refining
Before entering the refining process, rice bran must first undergo pressing or extraction to obtain crude oil. Rice bran contains approximately 16%–22% oil, but unlike soybeans or peanuts, it has extremely high lipase activity – if not treated promptly, free fatty acid (FFA) content will rise rapidly.
Common rice bran oil extraction equipment includes:
- Screw oil press: Generates high pressure through the continuous rotation of the screw shaft to squeeze oil from the rice bran. Suitable for small and medium-scale rice bran oil production.
- Rice bran extruder: Processes rice bran into porous pellets at 110°C–120°C, deactivating lipase enzymes to prevent rancidity while improving oil yield in downstream extraction processes.
- Roaster/conditioner: Heats and cooks the rice bran before pressing to reduce moisture, enhance aroma, and improve pressing efficiency.
For plants processing 20–30 tonnes per day or more, the solvent extraction method is typically adopted – rice bran is first stabilised in the extruder, then fed into an extractor to recover residual oil, reducing meal residual oil to below 1%, significantly outperforming pure pressing (which leaves 5%–7% residual oil).
Stage 1: Degumming – Removing the “Gum Barrier”
Degumming is the first step in rice bran oil refining. Its purpose is to remove phospholipids, proteins, and trace metal ions from the crude oil. Rice bran crude oil can contain 280–300 mg/kg of phosphorus. If not thoroughly removed, these gums will decompose during subsequent high-temperature stages, darkening the oil and degrading its flavour.
Studies show that degumming causes minimal oryzanol loss – only about 1.1%. This makes degumming a low-loss, high-gain step: it effectively removes impurities while sacrificing almost none of the oil’s most valuable nutrient.
Typical process: Crude rice bran oil is rapidly heated to approximately 70°C, mixed with 0.03%–0.2% phosphoric acid (85% concentration), cooled to around 40°C via an oil-to-oil heat exchanger, then mixed with 2%–3% dilute alkali solution (2.0%–2.3% concentration). After reaction, the mixture is reheated to 70°C and sent to a disc centrifuge separator to remove the gums.
Core equipment: Heater, oil-to-oil heat exchanger, disc centrifuge separator.
Stage 2: Dewaxing – The “Make-or-Break” Step
This is the most critical and distinctive stage in rice bran oil refining.
Crude rice bran oil contains 3%–12% waxes – several times higher than other vegetable oils. Rice bran wax is an ester of long-chain fatty acids and long-chain fatty alcohols, with a melting point of 62–69°C. The dewaxing step itself causes only minimal oryzanol loss (about 5.9%), but whether or not dewaxing is performed determines the final destination of the entire batch – whether it becomes bottled oil on supermarket shelves or is sold at a discount as industrial raw material.
Why is dewaxing mandatory?
Rice bran wax is not digestible and has no edible value. More importantly, waxes crystallise at low temperatures, turning the oil cloudy. For any bottled rice bran oil sold on retail shelves, clarity and cold-temperature stability are non-negotiable basic requirements. Without dewaxing, the oil may turn cloudy even at room temperature – and consumers will mistake cloudiness for spoilage or adulteration. Dewaxing directly determines the commercial value of rice bran oil.
Dewaxing process: Degummed oil is pumped into a winterisation tank (crystalliser), heated to 75–80°C with agitation to fully dissolve the waxes, then cooled slowly at 2–4°C per hour to 20–25°C, held at that temperature for a crystallisation hold period of approximately 14 hours to allow complete wax crystallisation. The wax crystals are then separated by a winterisation filter press to obtain dewaxed oil.
Two-stage winterisation can further improve results: the first stage dewaxes at 16–18°C, and the second dewaxes (degums) at 5°C to minimise oil entrapment in the wax.
Core equipment: Winterisation tank (crystalliser) (with slow-speed agitation and cooling coils), winterisation filter press (automatic plate-and-frame filter press).
Stage 3: Bleaching – Removing Pigments and Impurities
After degumming and dewaxing, the oil still contains pigments such as chlorophyll and carotenoids, along with residual metal ions and soaps. Crude rice bran oil typically appears dark brown, dark green, or greenish-yellow.
Bleaching uses adsorption: under vacuum, activated bleaching earth (typically 1%–3% by oil weight) is added at 90–110°C and mixed for approximately 30 minutes. Pigments and impurities are adsorbed onto the earth, which is then separated by a leaf filter.
Core equipment: Bleaching tank (vacuum agitated vessel), leaf filter, vacuum system.
Stage 4: Deacidification – The Fork in the Road for Oryzanol Retention
Crude rice bran oil typically has high acid value (KOH up to 25–26 mg/g). High acidity not only affects flavour but also accelerates oxidative deterioration.
This is the critical fork in the road for oryzanol retention. There are two technical routes for rice bran oil deacidification, and their impact on oryzanol retention is dramatically different:
Physical deacidification (steam distillation): Steam is injected under high temperature (240–260°C) and high vacuum to distill off free fatty acids. Physical refining loses almost no oryzanol – studies show that physically refined oil maintains oryzanol levels of 1.1%–1.74%, essentially unchanged from the original crude oil content (1.60%–1.74%). After heating at 180°C, physically refined oil loses 38.11% of its oryzanol, compared to 53.47% for chemically refined oil.
Chemical deacidification (alkali refining): Alkali is added to neutralise free fatty acids, forming soapstock which is then removed by centrifugation. Alkali refining causes 83%–95% oryzanol loss, leaving only 0.19%–0.20% in the refined oil. Alkali refining also causes oil loss of up to 55% and removes over 90% of oryzanol and other nutrients.
Conclusion: Physical refining is the only choice for preserving the core nutritional value of rice bran oil. With proper degumming and dewaxing pre-treatment, physical refining can retain over 80% of micronutrients (oryzanol, tocopherols, phytosterols).
Core equipment: Deacidification tower (physical distillation column) or alkali refining kettle, centrifuge separator.
Stage 5: Deodorisation – The Final “Polish”
Deodorisation is the final stage of refining, determining the finished oil’s flavour and stability.
Under high temperature (240–260°C) and high vacuum, direct steam (stripping steam) is passed through the oil, carrying away aldehydes, ketones, free fatty acids, and other volatile odour compounds.
After deodorisation, the rice bran oil is crystal-clear, neutral in flavour, and significantly more oxidatively stable – ready for bottling or use as a food processing ingredient.
Core equipment: Deodoriser tower (stainless steel construction with packing or trays), vacuum system (steam ejectors), fatty acid trap.
Five-Stage Refining Process Summary
| Stage | Core Equipment | Key Process Conditions | Primary Function | Oryzanol Impact |
|---|---|---|---|---|
| Degumming | Heater, disc centrifuge separator | 70°C, phosphoric acid 0.03%–0.2%, alkali 2%–3% | Removes phospholipids and gums | ~1.1% loss |
| Dewaxing | Winterisation tank (crystalliser), winterisation filter press | 75–80°C → 20–25°C (2–4°C/h), 14h crystallisation hold | Removes 3%–12% waxes | ~5.9% loss |
| Bleaching | Bleaching tank, leaf filter, vacuum system | 90–110°C, vacuum, bleaching earth 1%–3% | Adsorbs pigments and impurities | Minimal |
| Deacidification | Deacidification tower / alkali refining kettle, centrifuge | Physical: 240–260°C / Chemical: alkali refining | Removes free fatty acids | Physical: ≈0 loss; Chemical: 83%–95% loss |
| Deodorisation | Deodoriser tower, vacuum system, fatty acid trap | 240–260°C, high vacuum, steam stripping | Removes odours, improves stability | Physical: 38.11% loss at 180°C |
Why Dewaxing Is the Make-or-Break Step in Rice Bran Oil Refining
Each of the five stages has its importance, but dewaxing is the dividing line between crude oil and marketable product.
Dewaxing itself causes only about 5.9% oryzanol loss – far lower than the 83%–95% caused by alkali refining. But whether or not dewaxing is performed determines the final destination of the entire batch – whether it becomes a shelf-ready bottled oil or is sold as low-value industrial raw material.
Rice bran oil that has not been dewaxed can turn cloudy even at room temperature – and for bottled edible oil, that is unacceptable. Consumers will mistake cloudiness for spoilage or adulteration. Dewaxing directly determines the commercial value of rice bran oil.
FAQ
Q1: Which stage causes the greatest oryzanol loss in rice bran oil refining?
Alkali refining (chemical deacidification). Physical refining loses almost no oryzanol (≈0 loss), while alkali refining can cause 83%–95% oryzanol loss. Choosing physical refining is the key to preserving rice bran oil’s core nutritional value.
Q2: Is dewaxing mandatory for rice bran oil?
Absolutely. Rice bran oil contains 3%–12% waxes. Without removal, the finished oil will become cloudy even at room temperature. Undewaxed rice bran oil cannot be sold in the bottled retail market.
Q3: Physical refining vs chemical refining – which is better for a small rice bran oil mill?
Chemical refining requires lower equipment investment, making it suitable for small plants (1–10 TPD). However, if the goal is to produce high-quality, nutrient-retaining bottled rice bran oil, physical refining is the better long-term choice – despite slightly higher equipment costs, the product premium and nutrient labelling advantages can quickly recoup the investment.
Q4: What are the uses of rice bran wax?
Rice bran wax is a high-value by-product used in cosmetics (lipsticks, lotions), food coatings, polishes, and candle making. A well-designed dewaxing system can generate additional by-product revenue.
Q5: What pressing equipment is needed before rice bran oil refining?
The front-end pressing section typically requires a screw oil press, a rice bran extruder, and a roaster/conditioner. For small and medium-scale rice bran oil mills, the screw oil press is the most common pressing equipment; the rice bran extruder handles stabilisation to prevent rancidity and improve oil yield. Plants processing 20–30 TPD or more typically add an extractor to reduce meal residual oil to below 1%.
Q6: Why is temperature control so important in dewaxing?
The cooling rate (2–4°C/hour) and crystallisation hold time (approximately 14 hours) directly affect wax crystal integrity and filtration efficiency. Too rapid cooling creates fine crystals that are difficult to filter; too slow cooling extends production cycles and increases energy consumption.
What KMEC Can Do for You
Whether you are planning a 1 TPD small refining workshop or a 100 TPD large refinery, KMEC offers complete rice bran oil processing and refining equipment solutions.
Our product range covers the entire process from pressing to refining:
- Pressing and pre-treatment section: Screw oil press, rice bran extruder, roaster/conditioner, extractor
- Degumming section: Heater, oil-to-oil heat exchanger, disc centrifuge separator
- Dewaxing section: Winterisation tank (crystalliser) (with slow-speed agitation and cooling coils), winterisation filter press (automatic plate-and-frame filter press)
- Bleaching section: Bleaching tank (vacuum agitated vessel), leaf filter, vacuum system
- Deacidification section: Deacidification tower (physical distillation column) or alkali refining kettle, centrifuge separator
- Deodorisation section: Deodoriser tower (stainless steel), vacuum system, fatty acid trap
KMEC engineers can recommend the complete process route – from pressing to refining – based on your capacity targets, crude oil quality, budget, and product positioning, providing the optimal equipment configuration from single machines to complete turnkey EPC plants.
Contact KMEC today for a customised rice bran oil processing and refining equipment solution and quotation!
Data sources: [1] Journal of the American Oil Chemists’ Society (JAOCS) and related peer-reviewed studies