Producing high-quality extra virgin olive oil depends not only on fruit quality and processing technology, but also on the strategic use of processing aids - materials added during malaxation or paste handling that facilitate oil release. Although they modify the processing conditions, all approved processing aids share two essential characteristics: they do not remain in the final oil, and they do not negatively affect oil quality.

This article summarises the main categories of processing aids used in olive oil extraction, how they work, and when they offer the greatest benefit.

1. Understanding Processing Aids

Processing aids help overcome difficulties such as:

• High fruit moisture
• Low extractability
• Viscous or unstable pastes
• Difficult cultivars
• Low pumping capacity
• Excessive paste fluidity

The major classes of processing aids used in olive milling are:

1. Talc and microtalc powders
2. Common salt (NaCl)
3. Calcium carbonate (CaCO₃)
4. Citric acid
5. Enzymes (pectolytic and cellulolytic blends)
6. Combined strategies (e.g., enzymes + talc)

2. Talc and Microtalc Powders

How They Work

Talc is a natural hydrated magnesium silicate with a laminar sheet-like structure. When added to olive paste, it:

• Helps particles aggregate and improves paste structure
• Reduces paste adhesion to the malaxer and decanter surfaces
• Enhances oil droplet coalescence
• Reduces water and oil emulsification in the paste 

Research presented in the file shows talc:

• Reduces total pectin content in the paste, facilitating oil release
• Reduces cell wall proteins, further reducing emulsification and viscosity

Graphs demonstrate substantial extractability improvements across varieties such as Arbequina, Barnea, and Manzanillo when talc or microtalc is added.

When to Use Talc

Suggested when:

• Fruit moisture is >56%
• Difficult cultivars (e.g., Arbequina, Leccino, Picual, Hojiblanca or Nevadillo)
• Small crushing grids (4–5 mm)
• Extraction efficiency <85%
• Low decanter pumping capacity (<60%)

3. Common Salt (NaCl)

Mechanism

• Salt dissolves in the aqueous phase and:
• Increases the density difference between water and oil
• Improves phase separation in the decanter
• Enhances chlorophyll solubility—producing greener oils

• Increases extractability
• Low cost compared to talc
• No salty flavour in the oil
• Slightly increases polyphenols and stability 

1–3%, added during malaxation.

4. Calcium Carbonate (CaCO₃)

Mechanism and Use

A natural calcite mineral with very fine particle size (d50 = 2.8 µm). Its mode of action is similar to talc - promoting aggregation via adsorption.

Benefits

• Very high extractability
• Lower cost than talc
• Widely used in Spain with good results

However, CaCO₃ may:

• Increase oil oxidation (higher PV, UV values)
• Decrease polyphenols, stability and bitterness
  
• Produce very green oils
  
• Alter taste
  
• Raise pomace pH
  

5. Citric Acid

Citric acid acts both as a processing aid and a quality modifier:

Mechanism

• Generates a significant pH drop in the paste
• Causes degradation of pectin chains
• Enhances polyphenol partitioning into oil
• Possibly inhibits polyphenol oxidase (POD) activity 

Documented Effects

Research data shows:

• Higher total polyphenols
• Improved oxidative stability (Rancimat)
• Longer calculated shelf life
• Increased bitterness (chemical and sensory)

Application

• Add during malaxation
• Use 0.5–2.0%, prepared as a 30% water solution
  

6. Enzymes

Role in Extraction

Enzymes (typically pectinases and cellulases from Aspergillus spp.) break down:

• Pectin
• Cellulose
• Hemicellulose
• Middle lamella components (visualized in SEM

   

This releases oil trapped within cell structures more efficiently.

Key Benefits

• Dramatically improve extractability—especially in green fruit (MI < 3.5)
• Reduce paste viscosity

   

• Produce cleaner oil phases in the decanter
• Dry out pomace, reducing disposal weight
  
• Essential in early-season fruit with high pectin content 
  

Dosage 

• 300–500 ml/tonne, higher in dry years
• Increased dose for less mature olives

• Open oil plates to capture extra oil 

   

• Add 3–4% water if needed for decanter flow
• Reduce paste pump speed due to increased fluidity

7. Combining Enzymes and Talc

A combined approach often yields the best results.

Advantages

• Effective for excessively fluid pastes
• Enhances both structural correction (talc) and biochemical breakdown (enzyme)
• Produces cleaner oil with fewer suspended particles

• Both can be added simultaneously during malaxation
• Ensure enzymes are not dripped directly onto talc (to prevent localized deactivation)

8. Practical Guidance for Dosing

Talc and Microtalc

• Use a dispenser calibrated by kg/h and bulk density 
• If added manually, sprinkle slowly while filling the malaxer
  
• Add only to fresh paste, not oily paste
  

• Use dosing pumps capable of 8–10 L/h
• When added manually, introduce all at once at start of malaxation
• Dilute 4:1 or 5:1 with water

9. Conclusions

Processing aids are an essential - yet often underused - tool for olive oil producers aiming to optimize extraction efficiency, improve oil yield, and adapt to seasonal and varietal challenges. When applied correctly:

• Talc/microtalc stabilises paste and enhances separation
• Salt is a low-cost density modifier with positive quality attributes
• Calcium carbonate greatly boosts extraction but requires quality caution
• Citric acid enhances polyphenols and shelf life but may increase bitterness
• Enzymes are indispensable for green or high-pectin fruit
• Combined strategies (e.g., enzymes + talc) yield synergistic performance benefits