Monthly Archives: December 2013

The Difference – Sourness & Acidity

As mentioned in the last post, we are currently working on a water project that will become a little book. Part of that process is the inspiration for this article. During the project we organised blind taste testing sessions, and we drew up our own scoring sheet for participants to use. We did this in order to split up a few specific sections and try to achieve more objective and quantifiable results in relation to the tests we were doing.

Below is a link to one of the graphs that displays the sensory results of one coffee blind scored across three different waters – A, B and C.

Before testing began, I instructed the tasters to mark acidity in terms of how positive it was, i.e. that if the coffee has a lot of desirable acidity then mark high and to mark low for vice versa, for sourness I told them to mark this section in terms of intensity, low for little to no sourness and high for very sour

Coffee1_A,B,C (2)

As you can see, tasters responded quite differently to the same coffee when made with different waters, but what is of particular interest here, is the comparison between the sour and acidity columns for each water.

I think that the more useful and relevant the language when assessing and describing flavour experiences, the better. Often this just means using two terms rather than one, so they can complement and contrast each other. In essence two assessments are needed when one piece of terminology won’t do the job. I think “acidity” and “sourness” are a prime example of this.

A common statement is as follows – “sourness IS acidity”

When marking acidity on coffee we are not marking the sourness of the coffee, even though types of acidity can contribute to sourness. We are instead marking a quality that (if one is not familiar with as regards speciality coffee) could be misinterpreted as denoting sourness.
Although it’s possible for a coffee to have high acidity and also be sour, this doesn’t mean they are mutually exclusive. For instance, a creamy, nutty and floral coffee could have wonderful acidity; acidity that may be crisp, juicy, or sparkling. Here the coffee does not display much sourness but has great acidity.

This may sound a bit obvious but I think it’s worthy of a little exploration and this graph and the taste test we did were, I think, a good direct example of this topic rather than my more philosophical ramblings on the same topics in blogs such as – ‘Why Coffee Isn’t Overly Acidic’ (In hindsight, the wording ” Isn’t Overly Sour and Acidic” would have been a more accurate title) and “taste, flavour and perception”.

If you study the sourness and acidity results, they actually display the most opposing results out of all the sections. In that water B has the best acidity, closely followed by water A, but when we then move over to the sourness column, water B displays almost half the sourness score that A does.

This means that water A, although displaying a high, positive acidity also displayed high sourness; whereas Water B wins out on acidity but is accompanied by much less sourness. When we consider the other scoring sections we can deduce that water A brewed/produced a cup with good acidity but was also quite a sour driven cup. Whereas water B brewed/produced high/good acidity along with a more balanced and complex cup.

The breaking up of sourness and acidity was particularly useful for this test, if we only used acidity to mark the coffee, then A and B would have appeared closer in this area, but the sourness marker shows how different they really were.

It’s useful to also note that water C displayed abysmal acidity but comparable sourness to water B. This can then help infer that water C most likely displayed a dull heavy sourness, with little desirable acidity.

I find the interplay of these two markers fascinating as they rarely seem to match up and together I think they’ve told us more about what people were tasting on the day and how exactly the waters affected the same coffee. I wanted to share this graph as I think it nicely displays the independence of acidity and sourness in coffee.

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What About the Water?

Having been preoccupied with this question, its been a little while since I’ve written a post.

Water is naturally a huge part of a cup of coffee and the more and more we look at it the more it presents itself as one of the biggest players in a cup of coffees’ flavour.

We choose our coffees carefully, buying from roasters whose coffees we enjoy. On occasion we have really struggled with a few coffees. In these instances the coffees were not just a little flat or uninspiring, but were actively unpleasant.

The roasters we work with have always been receptive to feedback and keen to take part in a coffee dialogue, in the very rare instances when the coffees have been actively unpleasant, we’ve reached a difficult half way house where they are happy with the sample when brewed at the roastery, with there not seeming to be any of the same problems. In fact on these occasions they sound like different coffees altogether. After tasting coffee with them and trusting their judgment as they do ours, we were each taking part in a Sherlock-esque like hunt to find the culprit behind the nasty flavour transformation.

The increased ability to communicate about what and how we (any of us) are brewing, through the use of more exacting measurements, means it has become easier to rule out many parameters as the cause.

More often than not the clues lead to the same end – different water.

Can the water really be responsible for such a dramatic difference?

How often has the magnifying glass really been put on water? Sources such as the SCAA water book shed some light on the topic and we are all led to focus heavily on TDS (Total Dissolved Solids) as the measurement we should concern ourselves with, indicating that it is what has the biggest impact.

But what is TDS? A broad and vague measurement that indicates the total amount of minerals and particulates in the water beyond the pure H20. A brief look of bottled water labels will display that the number (TDS) can consist of largely different proportions across varying brands.

Would two waters with the same TDS, one in London and one in Bath, be the same? Would they impact on the coffee in the same way? What about the other numbers?

To explore these questions we were lucky enough to be able to enlist the help of theoretical chemist Christopher H Hendon. Chris has worked on varying projects with some focusing on taste products such as wine. He showed a keen interest in exploring water and coffee with us.

The resulting work has been fascinating and rewarding, with studies ranging from the use of atomic absorption spectroscopy, through to making the most of the U.K.’s largest super computer, as well as large blind taste testing data collection.

In order to fully present our piece on water and coffee, we need a different format to this blog. We are currently compiling an Ebook that will be released in the near future, I will make a note on this blog when the Ebook is released.

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