Comprehensive Guide to Edible Oil Refining Process

The edible oil refining process is a critical step in ensuring high-quality, consumable oils for various applications. This process removes impurities, enhances stability, and aligns the oil with regulatory standards. It is primarily divided into chemical refining and physical refining, each offering unique advantages and methods.

This article provides comprehensive details about the “Edible Oil Refining Process“, comparing chemical and physical refining methods, and highlighting their effects on soil quality and composition. Additionally, we will discuss how INVEXOIL’s “Engine Oil Refinery Services” and “Used Oil Re-refining Plants” incorporate similar principles and technologies to deliver high-quality outputs.

What is the Edible Oil Refining Process?

The edible oil refining process transforms crude oil into a consumable product by removing undesirable components such as free fatty acids (FFAs), phospholipids, pigments, and waxes. This is essential for improving the oil’s quality, stability, and shelf life, making it suitable for cooking and other uses.

Note: At the end of this article you can find in-depth scientific data on Edible Oil Processing in the form of academic tables.

Types of Edible Oil Refining Process

Edible oil refining happens in two main ways: Chemical and Physical Refining.

1. Chemical Edible Oil Refining

Chemical edible oil refining involves multiple stages: degumming, neutralization, washing, bleaching, dewaxing, and deodorization. Each step in the chemical edible oil refining process ensures the removal of specific impurities.

1.1 Degumming:

• • This step eliminates “gums” such as phospholipids, carbohydrates, and metallic ions.
  • Methods:
    • Water degumming: Removes hydratable phospholipids.
    • Acid degumming: Dissolves nonhydratable phospholipids using phosphoric acid.
    • Enzymatic degumming: Converts nonhydratable phospholipids into lysophospholipids.
  • Efficiency: Up to 95% gum removal through centrifugation.

1.2 Neutralization:

• • Treats crude oil with alkali (e.g., caustic soda) to neutralize FFAs, forming soap stock and removing impurities.
  • Reduces FFAs from 3.5% to below 0.05%.
  • Generates soap stock amounting to 2–4% of crude oil weight.

1.3 Bleaching:

• • Removes pigments and other impurities through adsorption using activated bleaching earth or carbon.
  • Operating at 100–120°C under vacuum ensures up to 95% pigment removal.
  • Process Insights: 
    • Adsorbent dosage varies between 0.5% and 2% of oil weight.
    • Optimal processing conditions: 100°C–120°C, vacuum applied for 20–40 minutes.
    • Achieves a 90% reduction in carotenoids and residual soap below 50 ppm.

1.4 Dewaxing:

• • Ensures clarity by removing waxes that cause cloudiness, especially in low temperatures.
  • Process Insights:
    • Cooling rate: 1–2°C per hour to achieve 10°C–15°C crystallization temperature.
    • Reduces wax content from 0.3% to below 0.05%.

1.5 Deodorization:

• • Uses steam distillation under vacuum to remove volatile compounds, enhancing flavor and stability.
  • Metrics:
    • Operates at temperatures between 180°C–240°C under vacuum (2–4 mmHg).
    • Reduces FFAs to below 0.01%.
    • Tocopherol retention ranges from 70% to 90%, dependent on parameters.

Key Benefits of Chemical Edible Oil Refining:

• Suitable for low-acidity oils.
• Ensures a high degree of impurity removal.
• Generates significant effluent requiring treatment.

2. Physical Edible Oil Refining

Physical edible oil refining is an eco-friendly and cost-effective alternative, suitable for high-acidity oils. It uses steam distillation to remove FFAs and other volatile compounds, bypassing the alkali neutralization stage.

The process consists of the same steps described in chemical refining, except for the alkali neutralization process. The difference between chemical and physical refining is that chemical refining consists of removing free fatty acids by adding caustic soda and separating the soap by centrifugation (mechanical separation), while physical refining, in the last step, removes free fatty acids and other compounds by steam distillation. , is process is also known as steam refining.

Physical refining of crude oils, therefore, overcomes the disadvantages of neutralization by sodium hydroxide. Indeed, this process, which is deemed to be eco-friendly, minimizes liquid effluent generation. Another advantage of this process over chemical refining is that it is more economical (e.g., fewer chemicals used, lower investment cost, lesser energy input, and improved yield). However, this process is not suitable for all types of oils since it is hypersensitive to the crude oil quality. (Hindawi Scientific World Journal. Volume 2022, Article ID 6627013)

Indeed, physical refining is used for oils with high acidity. Considering the phospholipids content, Dumont and Narine proposed two physical refining processes depending on the phospholipid content in the crude oil.

2.1 Degumming:

• Similar to chemical refining but optimized for oil quality.
• Water, acid, dry, and enzymatic degumming methods are used.

2.2 Bleaching:

• Removes residual impurities and improves oil’s visual appeal using adsorbents.

2.3 Deodorization:

• Steam distillation removes volatile compounds and ensures a neutral flavor.

2.4 Dewaxing:

• Optional step for oils prone to cloudiness.

Advantages of Physical Edible Oil Refining:

• High yield efficiency (up to 98%).
• Lower effluent generation.
• Eco-friendly and economical.
• Retains more bioactive compounds.

Challenges in the Edible Oil Refining Process

Despite advancements, the edible oil refining process faces challenges, such as nutrient loss and environmental concerns. Innovations are addressing these challenges:

• Enzyme-Assisted Degumming: Achieves 98% phospholipid removal efficiency.
• Eco-Friendly Adsorbents: Reduce waste by 30% without compromising efficiency.
• Advanced Deodorization: Retains up to 90% of bioactive compounds.
• Effluent Management Systems: Reduce environmental impact through efficient treatment.

Innovations in Edible Oil Refining

The edible oil refining process has evolved to incorporate eco-friendly methods and advanced technologies:

• Enzymatic degumming for improved efficiency.
• Adsorbents that enhance bleaching while reducing waste.
• Steam distillation techniques preserve the oil’s nutritional profile.

 

Detailed Examination of the Edible Oil Processing Stages: Expert Data Tables

Table: Undesirable Constituents in Edible Oil Removed During Refining

Component	Origin	Effect
Free fatty acids	Hydrolysis of triglycerides	(i) Taste, and smoke if heating (ii) Hydrolysis
Phosphatides (phospholipids)	Natural compounds	(i) Cloudy aspect (ii) Deposit a residue in the oil flavors (iii) Dark color if heating
Oxidation products	Oxidation of unsaturated fatty acids	(i) Undesirable flavors (ii) Stability (iii) Color—nutrition
Flavors	Natural compounds of seeds, autooxidation	(i) Odorous components (ii) Flavors
Waxes and pigments	Natural components of seeds	(i) Odorous components (ii) Flavors
Metals (iron and copper)	Technological pollution	(i) Oxidation catalysts (ii) Stability
Chemical pollutants Heavy metals Pesticides PAHs (B[a]P) Mycotoxins Dioxins	Pollution during storage transport and processing	(i) Safety toxicity

 

Table: Degumming (in Edible Oil Refining) Types, Description, and Application

Type of Degumming	Description	Application
Water Degumming	Uses water to remove hydratable phospholipids.	Suitable for oils with high hydratable phospholipids.
Acid Degumming	Uses acid to dissociate nonhydratable phospholipids.	Effective for oils with nonhydratable phospholipids.
Dry Degumming	Combines acid degumming with bleaching earth	Suitable for oils with low phospholipid content.
Enzymatic Degumming	Converts nonhydratable phospholipids into lysophospholipids using phospholipase C.	Efficient and environmentally friendly.

 

Table: Neutralization (in Edible Oil Refining) Properties and Values

Property	Value
Chemical Formula	R-COOH + NaOH ⟶ R-COONa + H2O
Free Fatty Acid Removal	High
Soap Separation	Mechanical (centrifugation)
Residue Elimination	Proteins, gums, carbohydrates, oxidation products, pigments
Bioactive Molecule Loss	Tocopherols, polyphenols

 

Table: Washing and Drying (in Edible Oil Refining) Properties and Results

Process	Description
Washing	Removes soap and impurities
Drying	Reduces moisture content
Temperature	358-363°K (85-90°C)
Moisture Level Target	<0.1%

 

Table: Bleaching (in Edible Oil Refining) Adsorbent and Description

Adsorbent	Description
Bleaching Earth	Removes colored pigments
Activated Carbon	Adsorbs organic contaminants
Silica	Adsorbs impurities
Temperature	353-393°K (80-120°C)
Contact Time	20-40 min

 

Table: Dewaxing (in Edible Oil Refining) Process and Description

Process	Description
Heating	Ensures oil is fully liquid
Cooling	Slowly reduces temperature
Filtration	Separates wax from oil
Temperature	283-288°K (10-15°C)

 

Table: Deodorization (in Edible Oil Refining) Process Parameter and Values

Process Parameter	Value
Temperature	453-513°K (180-240°C)
Vacuum Pressure	2-8 mmHg
Stripping Steam	High
Bioactive Molecule Loss	Tocopherols, sterols, polyphenols

 

Table: Comparison of Chemical and Physical Edible Oil Refining Processes in Different Aspects

Aspect	Chemical Refining	Physical Refining
Free Fatty Acid Removal	Alkali neutralization	Steam distillation
Effluent Generation	High	Low
Chemical Usage	High	Low
Economic Efficiency	Moderate	High
Sensitivity to Oil Quality	Moderate	High
Application	Suitable for all oil types	Suitable for oils with high acidity

 

Conclusion

Generally speaking, high-quality, safe, and stable oils for the achievement of consumer expectations regarding high quality and meeting the recent challenges of food safety depend directly on refining processes; both chemical and physical processes of refining have some potential advantages and drawbacks. That is to say, with broader applicability in wider areas, chemical refining bears the potential for higher consumption of more chemicals and increased generation of effluents. Conversely, physical refining has eco-friendliness and economic feasibility, though highly demanding proper care while dealing with crude oil quality.

The above content plus its professional and academic tables, we explored from the beginning of this long process of refining by degumming and neutralization, to bleaching, dewaxing, and deodorization, all contribute to the intricacy with which crude oils are made into refined edible oils. This holistic approach has implications for the final product in ensuring the safety, stability, and maximum retention of bioactive compounds.

Companies like INVEXOIL, which provides services in the area of “Engine Oil Refinery Services” and “Used Oil Re-refining Plants“, apply principles and technologies that can be relevant to edible oil refining in their respective areas for quality outputs in different fields. The goal of keeping to a minimum the level of harmful compounds and maintaining desirable properties is essentially in agreement with the main objective of producing high-quality oil products.