WOLFF WEEKLY VLOGG 004 | Peter Wolff gives the 411 on Green Bean Density
Today we’re looking at the density of green coffee and how we make this assessment as coffee roasters and take this information in to develop our roast profile. What density really means in terms of green coffee is we’re trying to understand from a cellular level, how compact is the fruit?
I guess the best way I can describe this to people is that if you consider that coffee grown at higher altitude is exposed to more sunlight and a lower oxygen environment. This really slows down the ripening process of the coffee and so this makes it, from a cellular level, more compact. So there’s a lot more cells compacted into the fruit and, therefore, it becomes harder and more dense. This does relate, or transfer across to, more refined acidity and the sugar content in coffee that we discussed earlier. As we move to a lower altitude the density of the coffee lessens, or it becomes lessened from a cellular structure. Therefore, it will absorb the heat a lot quicker we’re applying to the roasting process.
So one of the ways that we check that is we invest in a little thing that we have here - and here it is here. It’s actually a piece of PVC water pipe. It’s quite simple. We use the standard measurement of grams per litre, a thousand grams per litre. This represents a quarter of that standard measurement. What we do is we pop the water pipe on a set of scales, we fill it up till it gets to 250 grams and this represents the standard measurement.
All of our green coffee that comes in, we fill this up level, we put it on the scales, we take that measurement and we multiply it by four to take us up to the standard measurement and then we’re looking at how many grams a litre it is, or how hard the fruit is. A lot of average coffees would be about 680 grams a litre. This is what we call medium to high density coffee. Anything from 700 grams a litre above would be hard density coffee. This helps us understand how much heat initially do I need to apply to the coffee, or how little heat do I need to apply to the coffee if it’s a softer coffee.
A lot of the softer coffees are new of the more exotic varietals; a lot of the pacamara, the maragogype, the maracaturra - these types of varietals are a little bit softer. Unique processing methods; if you’re using a lot of monsoon coffees, you’ll find the monsoon coffees will be as low as 450 to 500 grams per litre. You can see there’s a big range in the coffee that you buy. It’s really important to understand at the very beginning, how hard is the fruit and how much resistance will it have to the heat energy that we’re applying to the roaster as part of the roasting process.
So altitude shouldn’t necessarily always be the guiding light. By having a simple process of adapting a roasting density and a green density, it really helps you understand, as a roaster, what you need to do to develop your overall strategy to roasting the coffee. I did touch on roasted density and that’s something we’ll talk about later.
