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Beyond Steam: Exploring Ethylene Oxide(ETO) and Sterilization Methods

Updated: May 3

ETO sterilization

The Dawn of Sterilization

Sterilization began as a simple yet effective means to extend the shelf life of food by killing microorganisms. Early methods were rudimentary, relying on sun-drying and salting to preserve food items, including spices. As trade expanded, the need for more reliable preservation methods gave rise to innovations like smoking and pickling.

The Rise of Heat-Based Sterilization

The discovery of pasteurisation and canning in the 19th century revolutionised food preservation. Heat-based sterilization became the cornerstone of the food industry, ensuring safety and longevity. Spices, being integral to global cuisines, were among the first to benefit from these methods.

Common Sterilization Methods in the Spice Industry(Why ETO is preferred?)

Today, the spice industry employs a variety of sterilization techniques:

  • Steam Sterilization: Utilises high-pressure steam to kill bacteria and is widely regarded for its efficacy and minimal impact on flavour.

  • Dry Heat Sterilization: Employs hot air and is best suited for whole spices that can withstand high temperatures without quality degradation.

  • Ethylene Oxide (ETO) Gas Sterilization: Uses ETO gas to sterilize spices, particularly effective for heat-sensitive products.

  • Irradiation: Exposes spices to ionising radiation, effectively eliminating microorganisms without raising the temperature.

A comprehensive list of all the sterilisation methods used in food industry

Sterilization Method

Process Description



Example Commodity

Steam Sterilization (Autoclaving)

Uses high-temperature steam under pressure.

Effective against all microorganisms.

May alter flavor and color.

Herbs like basil and oregano.

Dry Heat Sterilization

Utilises hot, dry air for sterilization.

Good for materials that can’t handle moisture.

Longer process; can affect quality.

Whole spices like cumin and coriander seeds.

Gamma Radiation

Employs gamma rays to kill microorganisms.

Deep penetration; no residue.

Requires specific facilities and safety measures.

Spices like chili powder and turmeric.

Electron Beam Radiation

Uses high-energy electrons for sterilization.

Quick process; suitable for surface treatment.

Limited penetration depth.

Ground spices and spice blends.

Chlorine Dioxide Gas (ClO2)

Uses ClO2 gas as a sterilant.

Effective; compatible with most materials.

Mainly for industrial use.

Industrial-scale spice processing.

Vapor-Phase Hydrogen Peroxide (VHP)

Uses hydrogen peroxide vapour for sterilization.

Effective; no toxic residue.

Requires specific equipment.

Delicate spices and botanicals.

Peracetic Acid Sterilization

Uses liquid or vapour peracetic acid.

Highly effective; non-toxic byproducts.

Can be corrosive; requires precautions.

Spices prone to microbial contamination.

Nitrogen Dioxide Sterilization

Utilises nitrogen dioxide gas.

Effective at low temperatures; no residue.

Specific equipment and safety needed.

Spices sensitive to heat and moisture.

Plasma Sterilization

Uses plasma state of gases for sterilization.

Low temperature; no residue.

Equipment cost and availability.

Heat-sensitive spice extracts.

Ozone Sterilization

Employs ozone gas as a sterilant.

Effective; environmentally friendly.

Requires generation and application systems.

Organic spices and herbs.

The Most Common and Preferred Methods

Steam sterilization stands out as the most common method due to its all-natural approach and ability to maintain the integrity of spices. Countries with stringent regulations on chemical residues, like those in the European Union, prefer this method for its clean profile.

The Most Expensive Sterilization Method

Ethylene Oxide (ETO) gas sterilization is among the most expensive due to the cost of the gas, the equipment, and the stringent safety measures required for its use. Despite its cost, it remains popular in countries like the United States, where its effectiveness against a broad spectrum of microorganisms is highly valued.

Country Preferences and Regulations

Different countries have varying preferences based on regulatory environments and consumer perceptions:

  • United States: Prefers EtO and irradiation for their broad-spectrum effectiveness.

  • European Union: Favours steam sterilization to align with strict residue regulations.

  • Asia: Utilises a mix of methods, with steam gaining popularity due to rising safety concerns.

Impact on Food Quality

While sterilization methods effectively ensure food safety, they can also impact food quality. Heat treatments may lead to the loss of volatile oils in spices, affecting flavour and aroma. Conversely, non-thermal methods like irradiation preserve these qualities but may raise concerns about food irradiation among consumers.

The Modern State of Sterilization

Innovation continues as the industry seeks methods that balance efficacy, cost, and quality preservation. The advent of non-thermal technologies like high-pressure processing and pulsed electric fields is promising, offering sterilization without the heat that can compromise spice quality.


The journey of spice sterilization is one of innovation driven by the unyielding pursuit of food safety and quality. As we look to the future, the spice industry remains committed to adopting methods that deliver the safest and most flavourful spices to consumers worldwide.


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