The key difference between oxygen absorber and silica gel is that oxygen absorbers absorb oxygen but not moisture, whereas silica gel can absorb moisture.
Oxygen absorbers and silica gel are important substances used in food packaging applications. An oxygen absorber or oxygen scavenger is a substance that we use to remove or decrease the level of oxygen in a package. Silica gel is a type of molecular sieve that has an irregular pattern of silicon and oxygen atoms with non-uniform pores.
CONTENTS
1. Overview and Key Difference
2. What is an Oxygen Absorber
3. What is a Silica Gel
4. Oxygen Absorber vs Silica Gel in Tabular Form
5. Summary – Oxygen Absorber vs Silica Gel
What is an Oxygen Absorber?
An oxygen absorber or oxygen scavenger is a substance that helps to remove or decrease the level of oxygen in a package. Oxygen absorbers are also helpful in maintaining product safety and extending the shelf life. They often come as small, enclosed packets or sachets (as shown in the following figure). Oxygen absorbers can be a separate component or a part of the packaging film or structure.
Figure 01: Oxygen Absorber
The composition of an oxygen absorber varies depending on the intended use, water activity of the product that it is intended to preserve, and some other factors. Typically, modern oxygen absorber packets use a mixture of iron powder and sodium chloride. However, it often includes activated carbon because it can absorb some other gases and organic molecules. This helps to preserve the food further and remove odors. The first oxygen absorber used was an alkaline solution of pyrogallic acid in an air-tight vessel.
There are several benefits of using oxygen absorbers: helping to retain the fresh-roasted flavor of coffee and nuts, preventing oxidation of spice oleoresins, preventing oxidation of vitamin A, C, and E, extending the life of pharmaceuticals, etc.
What is Silica Gel?
Silica gel is a type of molecular sieve having an irregular pattern of silicon and oxygen atoms with non-uniform pores. It is an amorphous form of silicon dioxide. Moreover, it contains nanometer-scale voids and pores. These voids may contain either water or any other fluid used in the preparation of the silica gel. E.g., gas, vacuum, other solvents, etc. Since the pore sizes are non-uniform, we can say that this molecular sieve has an average pore size of 2.4 nm.
Figure 02: Silica Gel
Silica gel has a strong affinity toward water, so we can use it as a desiccant. This material is very hard and translucent. However, it is considerably softer than silica glass or quartz. When silica gel is saturated with water, it remains in a hard state.
In commercial grade, we can find silica gel in the form of granules or beads. These beads have a diameter of a few millimetres. Sometimes, these beads also contain some amount of an indicator reagent that can change the colour of the beads when water is absorbed. As a desiccant, these beads are included in food packages as small packets to absorb water vapour inside the package.
What is the Difference Between Oxygen Absorber and Silica Gel?
The key difference between oxygen absorber and silica gel is that oxygen absorbers absorb oxygen but not moisture, whereas silica gel can absorb moisture. Moreover, oxygen absorbers are typically made of iron powder and salt, whereas silica gels are made of an amorphous and porous form of silicon dioxide.
The below infographic presents the differences between oxygen absorber and silica gel in tabular form for side-by-side comparison.
Summary – Oxygen Absorber vs Silica Gel
An oxygen absorber or oxygen scavenger is a substance that helps remove or decrease the level of oxygen in a package. Silica gel is a type of molecular sieve containing an irregular pattern of silicon and oxygen atoms with non-uniform pores. The key difference between oxygen absorber and silica gel is their ability to absorb moisture, i.e., oxygen absorbers cannot absorb moisture, while silica gel can absorb moisture.
Reference:
1. “Silica Gel.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.
Image Courtesy:
1. “Mitsubishi Gas Chemical oxygen absorber Ageless contents 20090104” By Dom0803 (talk) – Own work (Original text: I created this work entirely by myself.) (Public Domain) via Commons Wikimedia
2. “Silica-silica-gel-desiccant-dry” (CC0) via Pixabay