How to Avoid Bad-Smelling Coffee Bags: 5 Quality Checks Before Choosing a Supplier?

As a packaging manufacturer working closely with coffee brands, I often hear the same frustration: "Why do some coffee bags smell like chemicals or plastic?" Most buyers don’t realize the problem often starts with raw materials—and it’s avoidable.

To avoid bad-smelling coffee bags¹, check these five areas: raw material quality², solvent purity³, adhesive compatibility⁴, proper curing time⁵, and lamination strength⁶ tested by a tensile machine.

One buyer told me their entire shipment was rejected because the coffee bags had a strange odor. That wasn't just a packaging problem. It was a lost season. Let’s dive into how you can prevent this from happening.

How to make a bag not smell bad?

A clean-smelling bag starts from the inside—literally. It's about what goes into the bag during production.

The best way to avoid smelly coffee bags is to use virgin food-grade film, low-residue ink⁷ and adhesive, apply correct curing time⁵s for each material, and verify bonding with lamination strength⁶ testing.

Dive Deeper: Where the smell comes from

Problem 1: Recycled or second-hand raw material

Some suppliers cut corners by using recycled or leftover plastic. These materials are cheap, but they're not clean. They absorb all kinds of industrial smells, and the quality is inconsistent. I’ve seen bags made from such materials that couldn’t even print properly—the ink smears, colors fade, and logos look distorted. Smell aside, this already destroys brand value.

Problem 2: Poor-quality ink or adhesive

The ink and glue used in packaging must match the bag’s material. If the solvent purity³ is low or the ink and adhesive aren't compatible, even heat curing won’t help. After sealing, these bags continue to release volatile compounds. That's what creates the strong chemical smell.

Problem 3: Incorrect curing time⁵

Even if good materials are used, incorrect curing will ruin the result. Some suppliers rush the process. For complex laminated structures like pure aluminum four-layer films, we at IMIPAK set the curing time⁵ at 72 hours. For simpler metallized PET films, 24–48 hours is enough. Too short, and the solvents remain. Too long, and the bonding becomes brittle.

Problem 4: Lack of curing space and control

We maintain a controlled curing room⁸ with stable humidity and temperature to ensure even evaporation. After curing, we still rest the bags 1–2 days in open ventilation to remove any minor plastic smell—a normal result of food-grade plastic⁹ production.

By comparison, some factories skip this entirely. The bags go straight to packing and shipping. The result? That strong smell hits you when you open the carton.

How does a tensile tester¹⁰ check lamination quality of composite packaging?

We believe quality should be tested, not assumed. That’s why we use a tensile tester¹⁰ in our QC process.

A tensile tester¹⁰ checks if the laminated layers are strongly bonded. If layers peel too easily, it means poor curing or wrong adhesive. Weak bonding often leads to odor leaks and early bag failure.

Dive Deeper: Why this test matters

What we test

We cut a strip from a laminated roll, clamp both sides in the machine, and apply steady pulling force until the layers separate. This force is measured in Newtons.

If the peel strength is too low, we know the lamination failed. That means the bag might let in air, release solvent smell, or even delaminate during transport.

What weak lamination causes

• Bag layers separating under heat or pressure
• Solvent vapors leaking into the coffee
• Failure in vacuum sealing or degassing valve sealing
• Barrier properties degrading faster than expected

This is why we test each batch. Not randomly, but systematically. Especially for export bags where buyers can't afford customer complaints about odor or package failure.

Real case from our factory

One client in the U.S. was using a roll supplier who didn’t test lamination. Their bags kept splitting at the seams, and roasted beans smelled like glue. They switched to us. We checked the lamination strength⁶ of every batch, adjusted curing time⁵s, and within two orders, they saw a 100% drop in odor complaints.

Why IMIPAK refuses to use recycled material¹¹

Our principle is clear: no recycled film, no recycled ink, no recycled adhesive.

Recycled content may reduce cost by 10–20%, but it increases failure rate by 30–50%. Worse, it carries unpredictable smells—burnt, chemical, or sour—that ruin any premium coffee inside.

We use:

• Virgin plastic films certified for food contact
• Low-odor, low-residue adhesives
• Ink systems with strict solvent control
• Controlled curing rooms
• Force testing before dispatch

That’s how we eliminate unexpected bag odor and ensure consistency.

What can a buyer do before placing an order?

Before committing to a supplier, ask five questions:

1. Do you use virgin or recycled material¹¹?
2. What curing time⁵ do you set for my material type?
3. What kind of ink and glue system do you use?
4. Can I see tensile strength test data?
5. Can you send samples cured at full dwell time?

Good suppliers will have answers. Poor ones will avoid the topic.

What if the bag still has a slight smell?

Even with the best setup, new bags made of food-grade plastic⁹ may have a light, fresh plastic scent right after sealing. This is not harmful or unpleasant—it fades in 24–48 hours.

That’s why we recommend:

• Ventilating the bags briefly before filling
• Storing them in a cool, dry space
• Never rushing filling right after manufacturing

In fact, our bags are rested and checked again before we ship, so most clients never even notice that early scent.

Conclusion

If your coffee bags smell bad, it’s almost always because of poor materials or incorrect curing. Focus on virgin films, solvent control, proper curing, and force testing—and you’ll never deal with odor complaints again.