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What kind of packaging is best for freshly roasted coffee?

Coffee experiment

The packaging of our coffee has changed a couple of times over the course of our existence as we try to find the perfect balance of minimising our environmental impact and providing the best quality, freshest possible coffee. We started out with hessian which was entirely natural and could be composted but was expensive and time-consuming to produce. For a while we used plastic re-usable bags and lined paper bags, both of which better preserve the freshness of the coffee but which are not so good for the environment. Eventually we settled on paper kraft bags which are recycled and recyclable which means that even customers who do not compost can dispose of them in an environmentally friendly way. Paper is also breathable and as our coffee is fresh from the roaster, it means we can post it straight away and the beans can de-gas while in transit so the coffee is in optimum condition when it reaches you.

Given the development of our packaging over time, our interest was piqued by a conversation between Our Coffee Love and Thinking Bean on Twitter about using lined coffee bags with valves. We decided against this packaging as the valves can’t currently be recycled. However Our Coffee Love suggested in an article that the taste of coffee in a paper bag may be compromised as, alongside gases leaving the bag, they may also enter and affect the coffee within. Therefore an air-tight bag and one-way valve would protect the flavour of the coffee while still allowing the gases to escape.

Because we have a small roaster and can therefore roast on demand without a big batch going to waste, we decided we can help with this experiment.

The experiment

One batch of coffee – Daterra Bourbon Yellow, roasted at 220º for 22 minutes (this gave a medium or City roast level in the finished beans). The beans were from a single origin (Brazil Daterra Estate) and of a single variety (Bourbon) to give as much consistency in the roast and de-gassing as possible.

We split the roast in to 4 batches:

1) Unlined kraft paper bag of the kind we normally use

2) Lined paper bag with a one-way valve

3) Lined paper bag without a valve

4) Left to sit in open air for 24 hours before transferring in to a lined bag without a valve

During this time, we measured the level that the bag had swelled..

At the highest point of the bag at start of experiment:

1) 11mm

2) 16mm

3) 15mm

4) 16mm (after a 24 hour rest period)

90 minutes after roasting, both of the lined bags had started to swell with a 5mm and 9mm increase respectively. The unlined paper bag swelled a little but so little that it was barely noticeable and I only recorded a 2mm increase over the 3 days after roasting. Both of the lined bags (with and without valve) continued to swell throughout. Interestingly at the end of the 3 days of measuring, the lined bag with valve had a bigger increase in overall swelling with a 12mm overall increase compared to 10mm with the lined bag without a valve. This may seem strange however the taste test results may help to explain this. Coffee beans are porous and the taste of the beans in the lined bag without a valve was the most altered for the worst – the beans were stale and lacking in taste – could it be that the beans had re-absorbed some of the gases? It was out of the scope of this experiment to measure this but it’s interesting to consider for future testing.

The coffee which had the rest period of 24 hours before being placed in a lined bag without a valve swelled much more slowly, swelling by only 7mm after 3 days.

Taste test

The ultimate test in which packaging is the best is in the taste. We did a blind taste test of all of the coffees. We had meant to do this sooner but unfortunately were unable to do so and so the coffee was in its packaging for a week before the taste test. However we didn’t open it before tasting.

1) Unlined paper

On opening the bag, the aroma wasn’t as strong as it was when it went in. On tasting, these beans gave the smoothest taste and still tasted rich and fresh, however they lacked some of the brightness and fruitier notes compared to the valve bag and rest period bag.

2) Lined paper bag with a one-way valve

This had the richest aroma on opening and in the cup it was the richest in taste, retaining the fruity notes of the bean. It also had a buttery flavour to the finish that the other beans did not and which is something I hadn’t noticed in these beans before. This could be an anomaly or a result of being in the valve bag.

3) Lined paper bag without a valve

This gave the most interesting of the results. You might think that keeping the beans in a bag with no outlet for the natural gases to escape would preserve the flavour of the beans best, and indeed they did have the richest aroma on opening, however these beans were noticeably stale and flat in taste and had a much flatter crema than the other beans. The coffee had none of the richness or fruity notes that we’d typically find in this bean. It basically tasted like brown water.

4) Left to sit in open air for 24 hours before transferring in to a lined bag without a valve

The aroma on these beans was less rich than samples one and two however the beans retained a rich taste and many of the fruitier notes. It had some of the buttery flavour that we found in sample 2 but not as strong.

 

Conclusion

One of the arguments that roasters give for using a bag with a valve is to prevent the coffee bag from swelling excessively during transit and to prevent the risk of the bag exploding. However we found that valved bags do still swell and the difference between a lined bag with valve and lined bag without valve is minimal.

When it comes to the all important taste, it seems that a valve does have an important role to play. Coffee beans continue to release gases after they are roasted and these need to be released. The difference in taste between the lined bag with valve and lined bag without valve was huge and made the difference between a delicious coffee and an undrinkable brew so clearly having coffee beans sitting in those gases appears to significantly impair the flavour.

The difference that we personally were most interested in is between the unlined paper and the lined bag with a valve. When we did the taste test a week after roasting, the lined bag with a valve produced a noticeably fruitier flavour however we still found that the unlined paper beans still had a pleasing flavour and as mentioned above, came out as the smoothest. This may be because they are able to degas the most, although this means that they also lose some of the brighter, fruitier notes of the coffee. Interestingly these beans are of the same variety that Thinking Bean used in her degassing experiment which found that coffee beans continue to release CO2 for a significant time after roasting and more than previously thought. However this isn’t something we took in to consideration during the experiment.

We came to the personal conclusion that if coffee is to be left in its packaging or it isn’t being sold/dispatched to the customer shortly after roasting then a lined bag with a valve would help to keep the coffee fresher and preserve the taste. However as we always send the coffee out no more than 24 hours after roasting, we’re happy that the unlined paper bags allow the coffee beans to suitably degas while not losing out on too much flavour. We’re going to better repeat this experiment making sure we can do the blind taste test at 3 days just to be sure. We definitely would not consider using lined packaging that does not have a vent.

For very fresh coffee that is immediately dispatched, for us a valve just isn’t worth the environmental impact. While most recycling plants can now handle lined paper, the valves still can’t be recycled and small amounts of plastic cause huge environmental problems, particularly in the world’s oceans but also in landfills. Coffee is already feeling the effects of climate change so if we don’t take positive steps to reduce our environmental impact, there won’t be much good coffee left in the scarily near future.

We’d really like to repeat this experiment and be much more accurate in our approach.