Business Development Manager, Dom, explores different types of coffee bean defects following a trip to see specialty coffee roasters, White Star, in Belfast...
During a trip to Ireland I got into a conversation with Roaster/Consultant, James Price (White Star Coffee Roasters ) about green coffee defects, the efforts that White Star put into grading their coffee and how to get the best roast for their customers. It came to my attention recently that most coffee professionals aren’t educated in defects, as I was previously. This means they wouldn’t know how to identify promoters of negative flavours and what to remove/avoid.
So, I wanted to share my experience and research on the subject and put it into leymans terms.
The simplest, most cost effective way to reduce defects in coffee is to buy specialty. The raw ingredient will always have had a better farming experience, less variance in grade and size (if any) and the kinds of coffee roasters who roast this coffee would pick up defects while trying a sample of the coffee. The specialty supply chain is a better way to source your coffee and offers more to the farmers who in turn will take better care of the coffee. Theoretically this cycle will improve coffee quality further going forward as investment into sorting and drying processes yield better processes.
PRE ROAST DEFECTS- There’s a huge list of potential risk to green coffee; disease, pests, adverse weather, malnutrition and geographical conflict. Although we could sub-categorise each into several sub-defects I wanted to concentrate on the most common characteristics and how to find these.
The first and most common is a ‘Quaker.’ These are essentially an underdeveloped coffee bean. For several reasons the coffee bean may not have matured fully making it, denser and less soluble. These are being found earlier in the process now than ever thanks to UV lighting and keen coffee buyers rejecting them. The Quakers show as a bright white bean due to the structure of the bean not developing the fibres that make it a ‘green’ coffee bean.
The second most common defect being ‘Insect Damage.’ The coffee Bora beetle has plagued farmers for decades and is difficult to really control. These little bugs will bury into branches causing under development (quakers). Or to get the best feed they burrow into the cherry itself or feed on drying beds causing a breach of the outer membranes of the coffee bean. The appearance of insect damage is easy to identify as it genuinely looks like something has chewed on your coffee bean. Or it looks like the bean has been randomly drilled.
The third is Botanical Deviation. This category is less common now as there's a demand for natural mutation in coffee. ‘Peaberry’ and ‘Elephant beans’ are both natural mutations that happen by the will of mother nature. A ‘Peaberry’ occurs when only one coffee seed is formed in a seed. It named aptly for its size and pea like appearance. An Elephant bean occurs when both beans grow in the same ‘ovule/silver skin’ and is often called a ‘mother seed.’ A ‘shell’ is then formed in the other silver skin which will be underdeveloped and mis-shapen.
The Fourth is less common now but still somehow these can slip into a bag you might find in your shop. Mouldy or Stinkers. Part of the coffee drying process involves fermentation on the coffee fruit or mucilage. Done right this imparts a vast array of positive flavours on the bean. But as with all processes, if done wrongly can produce mouldy, sour and stinky coffee beans. The only way to identify the sours is to cup the coffee. The stinkers give off a pungent savoury odour that seems strange when inhaling a lung full of coffee aromas. The mouldy beans will also smell but will likely have visible mould or discolouration for you to pick out.
POST ROAST DEFECTS-
Many more problems can occur during roasting or may become more visible post roast.
These are the defects were looking at during the decanting of a fresh bag of coffee into what ever grinding system you may use. There are less post roast defects than green defects although some are repeated but with some variance in identification.
Quakers- We’ve mentioned this before, the under developed coffee bean. This will still show under UV post roast. However, you shouldn’t need a fancy torch. The coffee will be a few shades lighter than the rest of the roasted beans. As we mentioned earlier the bean density is higher and there's a different build up of cellular structure. So naturally the coffee bean will roast differently and will be easily identified by eye before crafting the coffee.
Underdeveloped roast- Where the coffee isn’t roasted fully. This is a colour thing, very much like quakers although the quakers will still appear lighter than an underdeveloped roast. The only identifyer is relative colour to other coffees you use.
Overdeveloped roast- This is a baked dark oily mess. This will be easily identifiable by its Starbucks style oils and dark chocolate shade. It isn’t specifically a defect as a burnt batch.
Insect damage- This will look exactly the same as it did on the green coffee, although due to the breached outer membrane some of the damaged beans will have burst like popcorn, but just leaving the outer shell.