The Key Role of Deacidification in Edible Oil Refining
Deacidification is a fundamental and indispensable step in the refining process of edible oils. Its primary purpose is to remove free fatty acids (FFAs) from crude oil—key factors that directly affect the oil’s quality, sensory characteristics, and shelf life. Excessively high FFA levels can cause the oil to develop an unpleasant rancid taste, accelerate oxidative deterioration, lower the smoke point, and potentially cause gastrointestinal discomfort in consumers.
National standards stipulate that the acid value of most edible oils must be below 0.3 mg KOH/g, while high-quality edible oils are required to have an acid value of ≤0.2 mg KOH/g. Since crude oil typically contains FFA levels ranging from 0.5% to over 25% depending on oilseed quality and extraction conditions, effective deacidification is non-negotiable for any commercial oil refining plant aiming to produce market-compliant, stable products.
Two Main Deacidification Methods in Modern Oil Refining Plants
1. Chemical Deacidification (Alkaline Refining)
This traditional method is based on the principle of acid-base neutralization. A precisely measured alkali solution (typically sodium hydroxide (NaOH) with a concentration of 8–14°Bé) is added to the crude oil to neutralize the free fatty acids, forming fatty acid salts (soapstock), which are then removed by centrifugation.
Technical Advantages:
- Relatively low initial investment in deacidification equipment
- Simultaneously removes phospholipids (gum), residual pigments, and trace metals
- Suitable for oils with high FFA content (up to 25%) and a wide variety of oil types
Key Parameters:
- The alkali dosage must account for both the neutralization of free fatty acids and the excess alkali required for the complete saponification of residual colloids—typically 5% to 25% higher than the theoretical dosage
- Operating temperature: 45–85°C, depending on the type of oil (palm oil requires higher temperatures)
- Residence time: 15–45 minutes in a continuous reactor
2. Physical Deacidification (Steam Stripping)
This advanced method removes free fatty acids through distillation under high-temperature (250–270°C) and high-vacuum (1–2 mbar absolute pressure) conditions. The process takes advantage of the significant difference in vapor pressure between free fatty acids and triglycerides at high temperatures.
Technical Advantages:
- Lower oil loss: typically 0.1%–0.3%, compared to 1%–2% for chemical refining
- Zero wastewater generation (environmentally friendly)
- For oils and fats with high initial free fatty acid content, deacidification efficiency exceeds 98%
- Preserves valuable trace components, including tocopherols (natural antioxidants) and phytosterols
Key Equipment Requirements:
- A packed distillation column with 316L stainless steel corrugated packing to achieve efficient mass transfer, with residual free fatty acid content as low as <0.05%
- Dual-stage steam ejector systems maintaining stable vacuum levels (1–2 mbar)
- High-efficiency heat recovery system to reduce operating costs
Ideal Applications: Physical deacidification is best suited for oils and fats with high free fatty acid (FFA) content and low colloid content, such as palm oil, coconut oil, and animal fats. To achieve optimal results, many modern oil refining plants employ a hybrid approach: chemical refining for seed oils and physical refining for lauric oils.
Critical Parameter Control in Deacidification Processes
Chemical Refining Parameters
Minor variations in process parameters significantly impact deacidification efficiency and oil loss:
| Parameter | Typical Range | Impact on Process |
|---|---|---|
| Alkali concentration | 8–14°Bé (±0.1% precision required) | Higher concentration increases soapstock entrainment; lower concentration increases emulsion risk |
| Mixing intensity | 60–150 RPM | Insufficient mixing reduces neutralization; excessive mixing creates emulsion |
| Reaction temperature | 45–85°C | Higher temperature reduces viscosity but increases saponification risk |
| Centrifugal separation speed | 5,500–7,500 RPM | Critical for complete soapstock separation |
Advanced Control Solutions: Huatai’s automated lye preparation system ensures precise concentration control, while online pH monitoring enables real-time adjustment of process parameters. Continuous lye refining technology significantly shortens oil-lye contact time (reducing saponification of neutral oil) and improves overall efficiency.
Physical Refining Parameters
- Pressure control: Must maintain vacuum levels at 1–2 mbar to enable effective FFA vaporization without exceeding oil degradation temperatures
- Steam consumption: 2–4% of oil weight per hour for thorough stripping
- Feedstock pretreatment: Requires degumming and bleaching prior to physical deacidification to prevent thermal degradation of phospholipids and impurities
- Proper steam distribution: Through specially designed nozzles ensures thorough stripping of FFA while minimizing oil entrainment and preserving nutritional components
Benefits of Effective Deacidification in Edible Oil Production
| Benefit | Technical Basis |
|---|---|
| Extended shelf life | FFA removal eliminates primary substrates for auto-oxidation, reducing peroxide value (PV) and slowing rancidity progression |
| Improved oxidative stability | The process reduces residual phosphorus (down to <5 ppm) and pro-oxidant metal ions (Fe<0.5 ppm, Cu<0.05 ppm) |
| Enhanced safety | Eliminates digestive irritants and raises smoke point to ≥215°C, suitable for high-temperature frying applications |
| Regulatory compliance | Meets Codex Alimentarius and national Grade 1 oil standards |
| Better sensory profile | Removes off-flavors and improves visual clarity (color reduction to <2.0 Lovibond red) |
Why Choose Huatai Oil Refining Equipment
With 38+ years of specialized expertise in grain and oil machinery manufacturing, Huatai has established a global presence serving over 70 countries worldwide. Our integrated process design solutions minimize refining losses, reduce energy consumption by 15–20%, and ensure the stable production of high-stability edible oils that meet international food safety standards. With superior quality, timely delivery, comprehensive after-sales service, and competitive pricing—Huatai is your trusted partner for sustainable edible oil processing solutions.