How the raw material reacts in a real food pack
A food manufacturer choosing an oxygen absorber will find plenty of sachets that look much alike. Some use iron powder, whereas others use a different active ingredient. Iron-based products are common; however, there are packaging situations where a non-iron-based product is worth considering. The difference becomes clearer when you look at what happens inside the pack and on the production line.
Will the absorber work at the humidity level inside your bag? Will it continue to function in cold storage? If the sealed food passes through a metal detector, will the sachet affect the check? These questions affect the choice as much as the price of the sachets. The nitrogen flushing and sealing conditions also need to be considered.
Here at Nanjing Tianhua Tech. Co., Ltd., we offer both types. We consider the food and its packaging conditions when selecting a formulation and capacity. The words “iron-based” and “non-iron-based” alone do not tell you which product will work faster, be safer, or suit your food better.
Figure 1 (left): OxyFree non-iron-based absorber Figure 2 (right): OxyFree iron-based absorber
Product photographs supplied by Nanjing Tianhua. The product categories follow our company information; the photographs do not show capacity, formulation, or operating conditions.
What happens inside the sachet
An iron-based oxygen absorber usually contains reduced iron powder, salts that help the reaction, a carrier, and components that manage moisture. With sufficient moisture and suitable conditions, iron oxidizes and consumes oxygen inside the sealed pack. This is the reaction on which the absorber depends. [1–3]
A non-iron-based absorber uses a different main oxygen-absorbing ingredient. Common examples include ascorbic acid, also known as vitamin C, and erythorbic acid, also known as isoascorbic acid, or their salts. These ingredients consume oxygen as they oxidize. For example, ascorbic acid can oxidize to dehydroascorbic acid under suitable conditions. The effectiveness of the reaction depends on the formulation, including its moisture, temperature, and pH requirements.
Non iron based products can be much differently from one another
Two products described as non-iron-based may have different formulations. In an ascorbic acid system, the other ingredients and moisture and pH conditions help determine the performance of the absorber. Some formulations also release carbon dioxide while absorbing oxygen. You need to check the particular product if that function matters to your packaging; it is not a feature of every non-iron-based absorber. [1–2]
Table 1. Key differences between iron-based and non-iron-based oxygen absorbers
| Criterion | Iron-based absorbers | Non-iron-based absorbers |
| Main active ingredient | Typically reduced iron powder | May use ascorbic acid, erythorbic acid or other organic systems |
| Mechanism | Iron oxidation consumes oxygen | Oxidation of the active ingredient consumes oxygen |
| Moisture conditions | Moisture is required; supplied externally or within the formulation | System-specific; not all operate without moisture |
| Metal detection | Conventional formulations may affect detection; validate equipment compatibility | Organic-active formulations often simplify compatibility, but full-pack testing is still needed |
| Rate and capacity | Depend on formulation, dose, sachet material, temperature and humidity | Also require measured data; category alone does not determine performance |
| Carbon dioxide behavior | Cannot be inferred from the iron-based label alone | Some formulations release carbon dioxide; others do not |
| Cost comparison | Consider usable capacity, time to target and production-line compatibility | Include formulation, size, inspection and packaging validation costs |
Note: This table compares common technologies, not test results for the products in Figures 1 and 2. [1–3]
A dry looking food does not tell you enough about moisture
Check the operating moisture range of the model you are buying. Iron needs moisture for its oxygen-absorbing reaction, but some sachets carry their own reaction moisture. These products can be used with low-moisture foods when the model is suitable. A non-iron-based product also has its own moisture requirements. Choosing that category does not remove the need to check them. [1]
Moisture content indicates the amount of water present in food. Water activity (aw) indicates the availability of water for reactions and microbial growth. They describe different things. Although food may appear dry, its appearance alone does not indicate the humidity that develops after sealing. If a desiccant is placed in the same bag, test it together with the oxygen absorber. It is necessary to determine whether the absorber continues to function as the desiccant absorbs moisture.
The food and the storage conditions guide the choice
Even with the same food, a change in the recipe, bag size, or storage temperature can change the type of absorber required. The applications below provide a starting point for testing. They do not assign each food to only one type of absorber.
Table 2. Typical applications and key validation points
| Application | Selection approach | Key validation points |
| Nuts, tea and dried foods | Evaluate iron-based or non-iron-based products suitable for low humidity | Low-humidity activation, flavor changes and desiccant compatibility |
| Bread, mooncakes and pastries | Screen both types against water activity and production-line conditions | Oxygen removal rate, sachet oil/moisture resistance and actual shelf life |
| Jerky, sausages and other processed meats | Prioritize detector-compatible options if metal detection follows insertion | Full-pack detection sensitivity, fat oxidation and storage conditions |
| Chilled meat in modified-atmosphere packaging | Define gas composition and color targets before choosing an absorber | Low-temperature performance and atmosphere changes; do not apply directly to high-oxygen color-retention systems |
| Pharmaceuticals and other sensitive products | Select dedicated products with relevant technical documentation | Stability, material compatibility, moisture effects and processing conditions |
Check the metal detector with the whole pack
If the sachet goes into the bag before metal detection, a conventional iron-based absorber may trigger the detector. A non-iron-based product using an organic active ingredient is worth evaluating in that situation. But test it with your actual food and packaging: salt, moisture, packaging materials and detector settings can all affect the result. There are also iron-based technologies designed for metal detector compatibility, so the category name cannot settle this question. [1,3]
During the trial, check that an ordinary pack passes and that the detector still finds the standard metal test pieces when they are added. A pack passing through the detector does not tell you whether the absorber was inserted correctly. Missing sachets need a separate check.
What I observed with our non iron based absorber in a microwave
I placed a non-iron-based oxygen absorber developed by our company into a microwave oven. When I removed it, the sachet had not swollen or leaked. I then opened the sachet, poured the contents into a glass Petri dish, and placed the dish in the microwave. Again, I observed no visible change.
That is what I saw with this sample under the conditions used. For a customer who wants an absorber to stay in a pack during microwave heating, this observation is a starting point for testing. It does not by itself establish that the product is safe under every microwave setting or that its oxygen absorption performance remains unchanged after heating. The intended power, heating time and complete food pack still need to be evaluated. Opening the sachet here was part of the observation, not a way to use it in food packaging.
How much oxygen it absorbs and how long it takes
Capacity indicates the amount of oxygen one sachet can take up. Speed indicates the time it takes to bring oxygen in the pack down to the target. Two sachets with the same stated capacity may work differently in a cold room or a low-humidity bag. Compare them at the same temperature, humidity, and starting oxygen level, using the same test method. Equal sachet weight does not indicate equal performance.
Work out how much oxygen the pack contains
Consider a bag with 500 mL of gas space. If that space contains air with approximately 21% oxygen, there is roughly 105 mL of oxygen to deal with. If nitrogen flushing brings the starting oxygen level down to 2%, the same space contains approximately 10 mL. The bag size did not change, but the starting amount of oxygen was very different. Neither calculation includes oxygen trapped in the food, released later, or entering through the packaging during storage.
The absorber needs sufficient capacity for the expected total, with some margin. Confirm the choice by testing the complete pack. When you see cc on an absorber specification, it usually refers to the volume of oxygen the sachet can absorb. One cc is one mL. It is not the weight of the sachet or the weight of food that the sachet can protect.
Choosing an OxyFree product for your own packaging
At Tianhua, we develop and manufacture oxygen absorbers and related preservation packaging products. The OxyFree products shown above include iron-based and non-iron-based options. For a sealed food pack, we consider the temperature, humidity, and amount of oxygen to be absorbed. If metal detection occurs after insertion, we include this in the trial as well.
When you contact us, please inform us of the food you are packing, its water activity, and the bag material and size. We also need to know whether vacuum packing or nitrogen flushing is used, the storage and transport temperatures, and the shelf life to be achieved. Please let us know where the sachet is located and when the pack is inspected. These details help us choose samples for the packaging conditions.
You can compare packs without an absorber against packs containing suitable iron-based and non-iron-based samples. Maintain the same food and packaging conditions. Record oxygen levels over time and check the food flavor and color, shape of the bag, and quality measures relevant to that food. This shows how the absorber performs in the pack you actually sell.
An absorber cannot compensate for a leaking seal or a film with an inadequate oxygen barrier. The food still requires appropriate microbial controls and storage temperature. A food-packaging sachet is not automatically suitable for pharmaceuticals, immersion in liquids, or high-temperature sterilization; these uses require separate confirmation. Neither type is edible. Keep the sachet intact during use and follow its instructions.