What Is an Oxygen Absorber and How Does It Extend Product Shelf Life?

Oxygen is one of the key factors contributing to quality deterioration in many food and agricultural products. The presence of oxygen inside packaging can cause fat oxidation, changes in color and flavor, deterioration of sensitive components, and, under certain conditions, an increased risk of growth of some microorganisms.

In products such as nuts, pistachios, tree nuts, dried fruits, snacks, and certain dry food products, controlling oxygen inside the package can play an important role in extending shelf life.

One effective technology for this purpose is the Oxygen Absorber.

An oxygen absorber is an active system that, once placed inside packaging, consumes oxygen present in the package headspace and, in some cases, oxygen entering from the surrounding environment, thereby reducing the O₂ concentration.

However, selecting a suitable absorber involves more than simply choosing a sachet of a specific weight. Absorption capacity, reaction rate, packaging type, headspace volume, storage temperature, initial oxygen concentration, and the intended storage period must all be considered when designing the system.

Why Is Oxygen a Problem for Food Products?

Oxygen inside packaging can react with various compounds in the product.

One of the most important processes is oxidation.

Oxidation can cause or accelerate the following:

• Fat rancidity
• Changes in odor and flavor
• Color changes
• Degradation of sensitive compounds
• Deterioration of sensory quality
• Reduced shelf life

This is particularly important for products containing unsaturated fats.

For example, nuts and dried fruits can be susceptible to oxidation due to their natural oil content.

Therefore, oxygen control can be an important component of a strategy to extend the shelf life of these products.

What Is an Oxygen Absorber?

An Oxygen Absorber, also known as an Oxygen Scavenger, is an active system designed to reduce oxygen levels inside packaging.

This system is commonly supplied in the form of a small sachet placed inside the product package.

Under suitable conditions, the oxygen absorber reacts with oxygen and removes it from the package atmosphere.

In a properly designed system, the objective may be to reduce the oxygen concentration inside the package from its initial level to a very low level.

However, the final oxygen concentration depends on several factors, including the absorber type, headspace volume, film permeability, and initial oxygen concentration.

How Does an Oxygen Absorber Work?

One of the most common oxygen absorption technologies is based on iron.

In this type of system, reduced iron oxidizes in the presence of oxygen and moisture.

The process can be represented in simplified form as follows:

Fe → Fe²⁺ / Fe³⁺ compounds

Overall, oxygen in the surrounding environment is consumed through iron oxidation reactions.

However, industrial formulations do not consist of iron alone.

Why Is Moisture Important for Oxygen Absorber Performance?

One important consideration in oxygen absorber design is the presence of an appropriate amount of moisture.

Many iron-based systems require water or moisture to react effectively.

Consequently, absorber performance may depend on water activity (aw), product moisture content, relative humidity inside the package, and sachet structure.

This introduces an important engineering consideration:

An oxygen absorber must be designed to achieve the required reaction rate and absorption capacity under actual packaging conditions.

Therefore, a formulation that performs well in a laboratory will not necessarily deliver identical results in a real product without testing.

What Is Oxygen Absorption Capacity?

One of the most important technical specifications of an oxygen absorber is its oxygen absorption capacity.

Capacity is generally expressed as the volume of oxygen the absorber can consume.

For example:

• 100 cc
• 300 cc
• 500 cc
• 1,000 cc
• 2,000 cc

Higher capacities are also available.

However, selecting the appropriate size should not be based solely on product weight.

At a minimum, the following factors must be determined:

Package Volume + Headspace Volume + Initial O₂ Concentration + Film Permeability + Storage Duration

How Do You Calculate the Required Oxygen Absorber Capacity?

For an initial estimate, a simplified relationship can be used to calculate the volume of oxygen in the package headspace.

The oxygen volume can be estimated using the following equation:

V(O₂) = V(headspace) × X(O₂)

Where:

• V(O₂) = Volume of oxygen present
• V(headspace) = Volume of the empty space inside the package
• X(O₂) = Volume fraction of oxygen

A practical design must also account for residual oxygen, oxygen associated with the product, the rate of oxygen transmission through the packaging film, and the intended storage period.

Therefore, absorber capacity should be selected with an appropriate safety margin and subsequently validated under actual packaging conditions.

Why Is Sachet Weight Not a Reliable Measure of Performance?

Two sachets with the same weight may have different oxygen absorption capacities.

For example, a 5-gram sachet is not necessarily equivalent to another 5-gram oxygen absorber.

Actual capacity depends on factors such as:

• Active ingredient percentage
• Type of iron
• Particle size
• Specific surface area
• Moisture content
• Formulation
• Sachet structure
• Reaction rate

For this reason, when purchasing or designing an absorber, it is better to evaluate oxygen absorption capacity and actual product performance rather than focusing exclusively on weight.

Oxygen Absorption Rate: Capacity Is Not the Only Factor

Two important characteristics of an oxygen absorber are:

Capacity

How much oxygen can it absorb?

Rate

How quickly can it absorb oxygen?

Suppose a package initially contains a relatively large amount of oxygen, but the product has only a few days to reach the desired oxygen level.

In this situation, an absorber with a very high capacity but a very slow reaction rate may not be the most suitable choice.

Professional system design must therefore balance capacity and absorption rate.

Applications of Oxygen Absorbers in Nuts and Dried Fruits

Nuts and dried fruits are among the major application areas for oxygen absorbers.

Products that may benefit from oxygen control include:

• Pistachios
• Almonds
• Walnuts
• Hazelnuts
• Raisins
• Dates
• Dried fruits
• Certain seeds

For these products, one of the primary objectives is to slow oxidation and preserve sensory and nutritional quality.

However, the product type, fat content, moisture content, water activity (aw), packaging type, and storage conditions must all be considered when selecting an absorber.

Oxygen Absorbers for Pistachios

Pistachios are an important export product for which packaging conditions play a significant role.

Key factors include:

O₂ + RH + aw + Temperature + Packaging

Oxygen can contribute to the oxidation of pistachio fats.

However, oxygen control alone is not sufficient to design an effective pistachio packaging system.

Moisture, water activity, film permeability, cold storage conditions, and transportation time must also be considered.

Therefore, a professional pistachio packaging system may combine:

Oxygen Management + Moisture Management + Appropriate Film

Oxygen Absorbers for Dates

Depending on the product type, moisture content, water activity (aw), packaging type, and supply chain conditions, dates may also benefit from oxygen management.

Storage requirements are not the same for all varieties of dates.

Therefore, absorber selection should be based on:

• Date variety
• Moisture content
• Water activity (aw)
• Package weight
• Headspace volume
• Film type
• Storage temperature
• Transportation duration

Are Oxygen Absorbers Suitable for All Products?

No.

The use of an oxygen absorber should be evaluated according to the actual conditions of the product.

Before selecting an absorber, it is advisable to assess at least the following factors:

The Role of Packaging Film

A common mistake is to rely entirely on the oxygen absorber to control oxygen levels.

In reality, the absorber and packaging film should be considered a single integrated system.

If the packaging film has high oxygen permeability, additional oxygen will continuously enter the package.

In this situation, the absorber must consume not only the initial oxygen but also the oxygen entering the package over time.

Therefore, professional packaging design must consider the film’s OTR (Oxygen Transmission Rate).

Oxygen Absorbers and Modified Atmosphere Packaging (MAP)

In some applications, oxygen absorbers can be used alongside Modified Atmosphere Packaging (MAP).

MAP and oxygen absorbers are not the same technology.

In MAP, the gas composition inside the package is controlled during the packaging process.

With an oxygen absorber, residual oxygen and, where applicable, oxygen entering the package are consumed by an active material.

Combining these technologies appropriately can help improve control of the package atmosphere in certain applications. However, the system must be validated according to the product type and packaging design.

What Is the Difference Between an Oxygen Absorber and Silica Gel?

These two products do not perform the same function.

Therefore, an oxygen absorber cannot simply be replaced with a desiccant.

Oxygen Absorber Safety

Oxygen absorbers are generally enclosed in a permeable sachet that allows oxygen to pass through while keeping the active materials separate from the product.

For food applications, the following considerations are important:

• Sachet material and structure
• Prevention of sachet rupture
• Prevention of powder leakage
• Mechanical strength
• Labeling requirements
• Conditions of use

Therefore, sachet design is just as important as the formulation of the active material inside it.

How Do You Choose the Right Oxygen Absorber?

The following process is recommended for selecting a suitable oxygen absorber:

Step 1

Identify the product.

Step 2

Determine the product weight.

Step 3

Calculate the headspace volume.

Step 4

Determine the initial O₂ concentration.

Step 5

Evaluate the film type and its OTR.

Step 6

Define the intended storage duration.

Step 7

Determine the required absorption capacity.

Step 8

Select an appropriate absorption rate.

Step 9

Test the absorber in the actual package.

Step 10

Measure O₂ levels over time.

This final step is particularly important.

Azarshid’s Oxygen Management Solutions

AZARSHID Oxygen Absorber Solutions

Azarshid develops oxygen absorber solutions for oxygen control in the packaging of dry products and products sensitive to oxidation.

Azarshid’s oxygen absorbers can be designed in different capacities for a variety of applications.

Potential applications include:

• Pistachios
• Nuts and dried fruits
• Tree nuts
• Dried fruits
• Dates
• Dry food products

One of the key advantages of this approach is the ability to design an absorber according to the product type, package weight, and storage conditions.

Conclusion

Oxygen is an important factor contributing to quality deterioration and reduced shelf life in many food and agricultural products.

An oxygen absorber can help reduce oxygen levels inside packaging and form part of a strategy to control oxidation and extend product shelf life.

However, actual absorber performance depends on multiple factors:

Formulation + Capacity + Absorption Rate + Moisture + Headspace + Packaging Film + OTR + Temperature + Storage Duration

Therefore, oxygen absorber selection should be treated as an engineering decision tailored to the specific product.

For products such as pistachios, nuts, and dates, the best results can be achieved when oxygen management is designed alongside moisture management, appropriate packaging, and proper storage conditions.

Do You Need an Oxygen Absorber for Your Product?

Azarshid can assess and recommend the appropriate capacity and format of an oxygen absorber based on your product type, package weight, packaging materials, and storage conditions.

AZARSHID – Active Postharvest Packaging Solutions