Oxygen vs. Moisture Barriers: Choosing the Right Protection for Your Product

You have spent months perfecting your product. You have sourced the best ingredients. You have worked with a top-tier designer to create stunning, eye-catching branding.

But there is a hidden threat that can ruin all of that hard work in a matter of weeks.

Great branding on your custom printed packaging gets a product off the shelf. However, great barrier packaging is what keeps the customer coming back. If your premium roasted coffee tastes stale, or your crunchy protein crisps arrive soggy, that customer will never buy from you again.

The secret to preserving freshness lies in the invisible science of flexible packaging: barrier films.

Think about your packaging format. You might use stand up pouches on retail shelves. You might use lay flat pouches for smaller sample sizes. You might even run printed rollstock through your automated packing machines.

No matter the format, the plastic is never just a single sheet. It is made of multiple ultra-thin layers of film laminated together. Each layer has a specific job. Some provide puncture resistance. Some hold the ink for your design. And some are engineered specifically to block the elements.

When designing your packaging, you must defend your product against its two biggest enemies: oxygen and moisture. Here is everything you need to know to choose the right protection for your food brand.

The Science of Spoilage: OTR and WVTR

To choose the right packaging, you first need to understand how the packaging industry measures protection. We use two main metrics.

1. OTR (Oxygen Transmission Rate): This measures how much oxygen gas passes through the packaging material over a 24-hour period. A low OTR means very little oxygen is getting in.

2. WVTR (Water Vapour Transmission Rate): This measures how much moisture (water vapour) passes through the packaging material over a 24-hour period. A low WVTR means very little moisture is moving in or out of the pouch.

Choosing the right packaging is about finding the perfect balance between OTR and WVTR. If you over-engineer your packaging with maximum barriers you don’t need, you waste money. If you under-engineer it, your food spoils prematurely.

Deep Dive: Oxygen Barriers (OTR)

Oxygen is essential for human life. However, it is a nightmare for packaged food. When oxygen interacts with food, a chemical process called oxidation occurs.

Oxidation is what causes sliced apples to turn brown. In packaged goods, oxygen causes fats and oils to go rancid. It strips away delicate flavours. It completely destroys the aromatic profiles of foods like coffee and spices. Furthermore, oxygen allows aerobic bacteria and mould to thrive.

Who needs a high oxygen barrier (Low OTR)?

• Coffee Roasters: Coffee beans release beautiful, volatile oils. Oxygen destroys these oils in days, leaving the coffee tasting flat and bitter.
• Nut and Seed Brands: High-fat foods like macadamia nuts, walnuts, and sunflower seeds go rancid very quickly when exposed to oxygen.
• Meat and Dairy: Beef jerky, biltong, and cheese require strict oxygen barriers to prevent mould growth and fat oxidation.

How we block oxygen:

To block oxygen, packaging manufacturers often use a special layer called EVOH (Ethylene Vinyl Alcohol). EVOH is a clear, highly effective barrier that stops oxygen dead in its tracks. Another common method is using a metallised film. This is a thin layer of aluminium applied to the plastic, which blocks both oxygen and light.

Deep Dive: Moisture Barriers (WVTR)

Moisture is a tricky element. Depending on your product, you either need to keep moisture completely out, or you need to lock it securely inside.

If your product is dry and crunchy, moisture from the outside air will make it stale and soggy. If your product is soft and chewy, dry outside air will pull the moisture out, turning your product into a rock.

Who needs to keep moisture OUT?

• Crisps, Crackers, and Popcorn: Nobody likes a chewy crisp. These products need a high moisture barrier to maintain their snap and crunch.
• Powders and Supplements: Protein powders, matcha, and baking mixes will clump together and harden if moisture gets inside the pouch.
• Freeze-Dried Fruits: These act like sponges. If the barrier is weak, they will pull moisture from the air and become sticky.

Who needs to keep moisture IN?

• Soft Baked Goods: Cookies, brownies, and artisan breads need to retain their internal moisture to stay soft and fresh.
• Pet Treats and Jerky: Semi-moist treats will become dangerously hard and unchewable if the packaging breathes too much.
• Cosmetics and Wipes: Face masks and wet wipes will completely dry out and become useless without a strict moisture barrier.

How we block moisture:

Thick layers of PE (Polyethylene) offer great moisture protection. For maximum moisture blocking, metallised films or pure aluminium foil layers provide an almost impenetrable wall against water vapour.

Real-World Examples: Matching the Barrier to the Product

Let’s look at how this plays out in the real world when deciding on your digitally printed packaging.

Product Type	Oxygen Risk	Moisture Risk	The Ideal Barrier Solution
Whole Bean Coffee	Very High	Low	High OTR barrier (EVOH/Metallised) + Degassing Valve.
Protein Powder	Moderate	Very High	High WVTR barrier. Metallised films work perfectly.
Granola & Oats	Low	High	Standard OTR, High WVTR. Clear films with good PE layers work well.
Beef Biltong/Jerky	Very High	Very High	Maximum barrier for both. Metallised or high-barrier clear films.

The Sustainability Factor

In the past, getting high barriers for both oxygen and moisture meant mixing many different types of plastics and aluminium together. While this protected the food, it made the packaging completely impossible to recycle.

Today, technology has caught up.

At ePac, we offer fully recyclable, mono-material PE (Polyethylene) pouches. Through advanced engineering, these mono-materials can now be coated with ultra-thin, recyclable barrier layers. A great example is recyclable EVOH.

This means you no longer have to choose between keeping your food fresh and meeting your brand’s sustainability goals. You can protect your product while protecting the planet.

Don’t let guesswork ruin your product’s shelf life. The right barrier film protects your margins, your brand reputation, and your customers’ experience.