Why is packaging airtightness a major issue in the biscuit industry?

In the food industry, maintaining quality through to consumption is a key issue. For biscuits, where crispness is a key characteristic, packaging integrity plays a crucial role. Inadequate packaging can compromise the product’s sensory qualities, leading to consumer disappointment and negative repercussions on brand image.

The fundamental concept is that the product is not limited to its contents, but also encompasses its packaging. For a biscuit, this “whole package” must ensure that its initial properties, particularly its crispness, are preserved throughout its shelf life.

Let’s take the specific example of dry biscuits. Typically, a cracker has a low moisture content, around 4%, and a water activity (aw) of approximately 0.15 at the time of packaging. The crispness of this type of product is directly related to this low water activity. However, beyond a certain aw threshold, generally around 0.36 (which can vary slightly depending on the product), the biscuit loses its crisp texture, a phenomenon known as crispness loss.

The crucial question then arises to determine how much water the biscuit can absorb before reaching this critical crispness loss threshold. The answer to this question is closely linked to the barrier properties of the packaging. There are two main mechanisms by which the external environment can alter the contents of a package: permeation and leakage.

Permeation is the process by which gases (such as oxygen) or vapors (such as water) pass through the packaging material itself. This phenomenon is intrinsic to the material used and is quantified by indicators such as the water vapor transmission rate (WVTR) or the oxygen transmission rate (OTR). Leaks, on the other hand, are physical defects in the packaging, such as micro-perforations, cracks, or seal defects. Even small defects can create a direct pathway between the interior of the packaging and the external environment.

The diffusion of oxygen through air is approximately a million times faster than its diffusion through polyethylene (PE), highlighting the significant impact even small leaks can have. These defects significantly increase the rate of material exchange with the environment, well beyond the intrinsic permeation of the packaging film.

What are the key factors that impact packaging airtightness?

Many factors, both internal and external to the packaging, influence this exchange rate. External factors include:
• Storage environment: Relative humidity and temperature conditions, as well as the presence of certain gases in the ambient atmosphere, play a major role. Tropical conditions (high temperature and high relative humidity) significantly accelerate the deterioration of moisture-sensitive products.
• Atmospheric pressure variations: Pressure changes can cause air to flow into or out of the packaging, particularly in the presence of defects.
• Mechanical and physical stresses during transport: The weight of stacked packages, friction and abrasion, as well as altitude variations, can damage the packaging and cause leaks.

Internal factors related to the product itself can also influence exchanges with the environment.
To assess the impact of these exchanges, the concept of the half-life of a protective atmosphere (t1/2) is relevant. This is the time required for half of the initial atmosphere inside the package to be replaced by ambient air. This half-life is inversely proportional to the surface area of ​​the leak and proportional to the volume of the package’s headspace. Therefore, smaller packages are more quickly affected by leaks.

What other risks are there with cookies?

In addition to humidity, other risks are associated with leaky packaging:
• Oxidation: Ambient oxygen can alter certain components of biscuits, leading to rancidity of fats, for example.
• Bacterial growth: Excessive humidity inside the packaging can promote the growth of microorganisms.
• Infestation: Packaging defects can allow insects to enter.

Faced with these multiple challenges, it is crucial to adopt a rigorous approach to ensuring the airtightness of packaging. Analyzing leak test data is a fundamental step. Accurately quantifying leak rates and statistically analyzing them allows for the evaluation of the performance and reproducibility of the packaging process. By examining the statistical distribution of leak rates across a series of packages, it is possible to identify potential problems related to packaging machinery or packaging materials. For example, significant dispersion in leak rates may indicate a lack of control or variations in the process.

The use of statistical distributions also allows various stakeholders in the supply chain (production, quality, film suppliers) to communicate effectively to improve the process and achieve quality objectives. A rigorous leak testing methodology, combined with data collection and analysis, is a powerful tool for optimizing cookie shelf life and ensuring consumer satisfaction.

In conclusion, packaging hermeticity is a determining factor in maintaining cookie quality, particularly crispness. Understanding mass transfer mechanisms, distinguishing permeation from leaks, and rigorously analyzing leak testing data are essential steps to guaranteeing the consumer promise and ensuring the commercial success of products.

A proactive, data-driven approach not only prevents product spoilage but also saves money by optimizing processes and reducing food waste.

This text summarizes the presentation by Eric Schaller, CEO of Anéolia, at the Biscuit People conference, held from April 9 to 11, 2025, in Milan.

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