Road Test: Compostable Coffee Bags

When it comes to storing roasted coffee; how do compostable bags compare with the bags we've been using?

The environmental benefits of compostable bags are tantalising, but few people will live with a product that doesn't do its job. So, here's our road test of a PLA coffee bag.

For the record, the bags tested carry the TUV Austria OK Compost Home certification. This means 90% degradation in six months at temperatures between 20 and 30 degrees Celsius. (The equivalent commercial standard specifies temperatures between 55 and 60 degrees.)

The bags also comply with toxicity and chemical standards, which control heavy metals and other harmful substances.

First Impression: It's a Bag

First impression is that it's a bag(!). The Kraft paper looks and feels like regular Kraft paper. The zip seal is effective.

The most visible difference to our current bags is the interior, where the elimination of metal becomes obvious. It's quite a change from the old shiny silver look.

Our samples didn't contain a one-way valve. This contributes to the bags weighing less than our current bags but, more importantly, it adds uncertainty to our test results.

More on that later.

We Put Them on a Shelf

Because we could, we tested both a dark roasted Arabica blend and a lighter single origin (Ethiopia Yirgacheffe). Our method was to take coffee beans the day after roasting, split them between compostable and traditional bags, and put them on a shelf.

The environment was dry with moderate room temperatures.

Time passed...

Seven weeks to be precise.

If time had allowed, we may have packed a larger number of samples and tested them at various intervals.

What we Found

We opened the dark blend first, and found that the beans' appearance was identical in both bags. Opening the PLA bag released unpleasant, stale, almost rancid aromas. The regular bag presented a much more appealing roasted coffee fragrance. It's unclear whether this is related to the presence of a one-way valve in the old metalised bag.

Shots through our La Marzocco FB80 espresso machine looked dark for both samples, as appropriate for the age of the coffees. Surprisingly perhaps, the crema on both samples was reasonably thick and lingered well. Despite the bean's aroma, preferences from five blind tasters on day one leaned a little to the new PLA bags on the basis of sweetness and body.

Day two, and the unpleasant aromas of the PLA coffee had dissipated. Taste tests yielded no material variations between the samples. The coffees maintained typical levels of crema, roasty bite and body.

The Ethiopian beans presented almost identically in all respects upon opening. Variations reported in blind testing couldn't be attributed to the bags.

Day two, and there were no discernible differences between the Ethiopian samples with both performing true to character.

Both sets of samples were tested on subsequent days but it wasn't a sufficiently controlled process. Also, with the benefit of hindsight, we'd love to see a test where bags are refrigerated or stored in an environment with higher humidity.

The Final Score

We set out to determine whether a home compostable bag would be effective coffee storage. Clearly in our scenario, the answer is yes.

We wouldn't be surprised if it's raised other questions in your mind. We assumed that the bag concept has merit, but this is one of many related issues we didn't address. Perhaps you have some experience that can benefit others.

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