February 2014 - impact of heat on roasted coffee beans

Date Posted:1 February 2014 

heat and roasted coffee

Last summer (2013) was particularly challenging for us dealing with excessive heat over prolonged periods in Feb and March.

When we talk about heat, it's the sustained warmer temperatures during the day and at night that cumulatively build up the overall heat in our warehouses.

We have cooling installed in our factories to reduce the impact of heat adversely affecting our products - for managing both our raw materials and roasted coffee beans.

Controlling the environment temperature has long been a feature of our business and one of the key differentiators over our competitors.

That's right, its fair to say that barely any other coffee roaster in Australia would have a temperature controlled warehouse.

So far this summer, December 2013 was quite mild but we have been hit some exceptionally hot conditions in January and February 2014.

In mid-Jan 2014, the temperature outside our warehouse exceeded 50 degrees C. The picture below was taken on January 17, 2014.

 

Why is it important to reduce the impact of high temperatures ?

Coffee beans, whether they are raw or roasted, do not tolerate exposure to high ambient temperatures for extended periods of time (hours or days).

Raw (Green) Coffee Beans

In the case of the raw coffees, they sweat, lose moisture, create or accelerate the production of existing mould or fungus and generally lose quality.

When coffee is transported from origin to Australia, it is inside containers. 

Sometimes, these containers sit on docks, or warehouses for weeks at a time and the temperature inside the container can exceed 70 degrees - think of a car parked in the sun as most coffee is grown in hot locations near the equator.

Typically, the freshly processed raw coffee beans have high moisture levels, so when combined with the heat and restricted airflow inside of the container, it becomes very humid.

The introduction of lined bags does not adequately address the heat exposure problem - the bag liners are primarily used to reduce the exposure to airborne taints such as chemical vapours, exhaust fumes, etc. and other pollutants that are common in transportation and storage.

Raw coffee beans exposed to heat for long periods lose cup quality. 

When roasted, they can lack body, acid, aroma and can appear "flat".

Whilst it is true that raw coffee beans can last 3 years, we ensure our stock is consumed within 3 - 4 months. During the warmer months in Melbourne, we may hold slightly lower raw coffee bean inventories, but again this places additional risks due to limited seasonal crop availability.

Roasted Coffee Beans

Once temperatures rise above 25 deg C, our testing has shown that roasted coffee starts to degrade much faster than normal. Of course, there will be someone out there who thinks the science behind this is statement is flawed, however, we know from what we see and taste.

Raw (green) coffee beans are roasted at high temperatures - 200 to 450 degrees Celsius, so it only makes sense that exposure to warm temperatures is only going to take the roasted coffee beans into another zone that was not intended by us as the roasters.

We see some acceleration of the oxidization process, e.g. a speedup of degassing, increased CO2 production that may manifest itself in swelling of the coffee bag (although that is normal and can occur in cooler conditions - sometimes it's the nature of the 1-way valve as some activate on different pressures).

Roasted coffee beans that may have experienced some heat exposure could also have higher levels of oil on the outside of the beans. If the coffee is within 2 weeks from Roast Date and is oily (excluding decaffe as that goes oily very quickly) then it is a good chance the coffee has been exposed to elevated levels of heat.

Our business model of holding minimal roasted stock works to our advantage during the warmer periods.

Generally, roasted coffees are barely 24 - 72hrs old in our warehouse and our high turnover means nothing sits for any period.

For our roasted coffees, we take extra care to ensure these are not exposed to high temperatures.

We roast at night and on those few nights a year when it's 30+, we do not even try to run the roaster - despite our powerful cooling system, the concept of having coffee beans exposed for even short times means we are dealing with risks.

There are of course aspects we cannot control - such as when the pallets of coffee are loaded each afternoon into the AusPost collection vans.

We do our absolute best to ensure parcels are packed and stored in cooler conditions right to the minute the vans arrive for collection.

On days of high or extreme ambient temperatures, an AusPost van may be like your car in terms of high heat during periods when the coffee is being transported or handled. Similarly, if your parcel has been sitting in one of the many AusPost warehouses or local post offices, there may be no air-conditioning outside of business hours to keep the parcels below 25 deg. C.

How to store your coffee at home or work

In another article I wrote some time ago (I think it was 2009) explains the basic principles of storing coffee.

Click on the link here to read the article Storing Coffee

The #1 issue we continue to encounter is the Old Wives Tale of storing the open packs of coffee in the fridge. Please DO NOT store coffee beans in the fridge.

Closely following behind the fridge issue is #2 - freezing packs of coffee beans.

There are many conflicting views on this topic. Unfortunately, you have people who have gone through the exercise of freezing packs of coffee beans and then standing up on the soap box to tell the world "yes, freezing coffee beans works perfectly".

I disagree with those who think freezing works and for two very simple reasons

Changes in the coffee bean cell structure, specifically the effects of moisture on the thawing.

Generally, the average coffee drinker does not have a developed, calibrated or trusted palate - for many people it's simply a case of........yep, it tastes like coffee and as long as there is no bitterness, that's "good enough".