Coffee Export

GrainPro & Barrier Liners

Hermetic liners are now standard on East African specialty lots. This page explains the mechanism, the honest limits, and the handling requirements that decide whether the liner does anything at all.

Last reviewed August 20262 min read

Quick answer

A hermetic liner is a multi-layer plastic bag placed inside a jute sack to restrict moisture and oxygen exchange. GrainPro is a brand name that has become the generic term. Liners meaningfully extend the useful life of green coffee — but only if they are properly sealed and remain undamaged.

How they work

A hermetic liner is a multi-layer plastic film engineered for low water-vapour and oxygen transmission. Sealed around the coffee inside a jute bag, it slows the two processes that degrade green coffee fastest: moisture exchange with the surrounding air, and oxidation of the bean’s lipids.

The mechanism is straightforward — restrict transmission, slow the reactions. It does not stop them. A liner buys time; it does not preserve indefinitely.

Lined versus unlined
	Jute alone	Jute + hermetic liner
Moisture exchange	Free — bean equilibrates with ambient	Strongly restricted
Oxygen ingress	Unrestricted	Substantially reduced
Odour uptake	Possible	Largely prevented
Behaviour in humid transit	Gains moisture	Largely isolated
Cost per bag	Lower	Higher
Failure mode	Gradual	Sudden if punctured
Waste at destination	Biodegradable, reusable	Plastic waste stream

When a liner earns its cost

1Storage beyond about three months at destination — the point where unlined coffee starts to show measurable change in most warehouses.
2Humid destinations, where unlined coffee will gain moisture rather than simply equilibrate.
3High-value lots, where the liner cost is small relative to the coffee and the downside of degradation is large.
4Long or multi-leg transits, particularly routings that cross climate zones or involve transhipment delays.
5Naturals and honeys, which are generally more sensitive to moisture migration than washed lots.

Conversely, for commercial coffee turning over in weeks in a temperate warehouse, a liner adds cost and a waste stream for limited benefit.

The handling requirement

A punctured liner is worse than no liner

An intact liner isolates the coffee. A punctured one creates a partially enclosed pocket where moisture can accumulate without ventilating away — which is a better environment for mould than open jute. Liners must be sealed properly at filling and must survive handling.

Seal method matters — heat sealing, folding and tying are not equivalent. Specify it.
Hooks are the classic liner killer. Bag handling with hooks should be prohibited for lined parcels.
Container floors and walls should be checked for protrusions before stuffing.
Stack pressure on lower layers can stress seams over a long voyage; stow pattern matters.
Inspect a sample of liners at arrival, not only the coffee — a failed liner explains an unexpected moisture reading.

Specifying liners

Liner type: Hermetic multi-layer barrier liner — state that it is not a plain PP liner
Seal method: Heat-sealed, or folded and tied to an agreed method
Handling: No hooks; agreed handling instructions on the bag marking
Inspection: Liner integrity checked at stuffing and recorded
Moisture and aw at filling: Recorded — the liner preserves the condition it was sealed at, good or bad

A liner cannot improve coffee

It preserves whatever condition the coffee was in when it was sealed. Sealing a lot at 13% moisture into a hermetic liner traps that moisture with the coffee. Drying discipline comes first; packaging preserves the result.

Lined presentations across our origins

Hermetic liners are standard on our specialty separations and available on commercial parcels. Tell us your storage plan and we will recommend.

Green coffee packaging

Frequently asked questions

What is GrainPro?

A brand of hermetic multi-layer liner used inside jute bags to restrict moisture and oxygen exchange. The name is widely used generically for barrier liners of any manufacturer, in the way that other trade names have become generic terms.

How much longer does coffee last in a hermetic liner?

There is no fixed figure — it depends on the starting condition, the storage environment and the coffee itself. What a liner reliably does is decouple the coffee from ambient humidity swings, which is the main driver of degradation in most warehouses.

Can a liner fix high-moisture coffee?

No. It preserves the condition the coffee was sealed at. Sealing a lot at too high a moisture traps that moisture with the coffee and can make matters worse. Drying discipline comes first.

Are liners recyclable?

Multi-layer barrier films are difficult to recycle through most municipal streams because of their construction. For buyers with packaging-waste commitments this is a real consideration, and worth weighing against the storage benefit for each parcel.

Tell us the coffee you need

Lots can be specified by origin, region, process, grade, screen, moisture, defect tolerance, crop year and packaging. Send what you know and we will confirm what each origin realistically supports.

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