July 2, 2015

Barista-Certified Rules for Dialing In A Coffee Grinder

If you’ve spent time in a coffee shop, chances are you’ve overheard a barista mention dialing in a coffee grinder. This refers to the process of balancing dose, grind, output weight, and extraction time to achieve a delicious tasting coffee. In this article, I’ll focus on dialing in a coffee grinder for espresso, and how variables can affect its taste.

SEE ALSO: The Barista Guide to Buying a Home Espresso Machine

Equipment Standards and Settings

Espresso extraction involves forcing hot water through a finely ground coffee puck to produce a viscous, intensely flavoured drink. Many factors influence an espresso’s taste. We’ll assume a 6.5 bar pump pressure, 15g VST baskets, and 93 °C water temperature at the group head. Although it’s different from industry norms, it stays the same for every espresso brewed and produces excellent results.

Dose and Grind

The first stage of dialing in a coffee grinder is to adjust the grind. It starts with the setting used for the previous beans, unless there’s a vast difference in their respective roast profiles. I use a starting dose of 16g and a 50% brew ratio initially. This is the dosage weight as a proportion of the espresso. A 50% with a 16g dose would yield a 32g espresso.

Coffee scales

Weighing your shots when dialling in is a must.
Credit: @repackespresso

I’ll pull a shot using this recipe, and, if it’s within my target time range (usually 28-35 seconds), taste it. If extraction is too slow or quick I’ll toss the shot, adjusting the grind until it hits my time parameters.

I’ll adjust dose, grind, output weight and extraction time from there in order to optimise the espresso. It’s worthwhile considering what we mean by extraction yield and the terms, “over extraction” and “under extraction”.

How Dialing In Impacts Extraction and Taste

Extraction yield refers to the percentage by mass of the coffee grounds that are dissolved in the espresso. If you start with 20g and found used grounds after extraction and removing retained moisture, you’d have a 20% extraction yield. 20g minus 16g equals 4g, which is 20% of the input dose of 20g).

Over extraction and under extraction refer to yields that fall outside of general taste preferences and, consequently, are not absolutes. Many studies have found that people have a preference for coffees that have extraction yields in the 18-22% range. However, it has recently become increasingly common for specialty coffee shops to extract at higher yields—up to 25%—so it’s important to remember that these aren’t set in stone.

In relation to dialing in a coffee grinder, I’ll be looking to find the optimum extraction yield for a given coffee, and, again, there are no absolutes here; some espressos taste their best at 19%, others at 23%. The important point is to recognise when the optimum extraction has been achieved.

Specialty coffee is usually roasted fairly light which, due to the lower solubility of the beans, makes it harder to extract than traditional dark espresso roasts. Shots pulled early in the dialling in process with light roast coffees, then, are more often under extracted than over-extracted. This typically reveals itself in an overpowering acidity and astringency. Sweetness, also, will often, be absent. We can counter this in a number of ways, but the primary one is to grind a little finer. This increases the surface area of the grinds and raises the extraction yield. We can also reduce the dose slightly—by 0.5g, perhaps—which provides the water with a lower workload, and, again, increases extraction. The brew ratio, at this point, needs to remain the same, so if we drop from 16g to 15.5g, we need to decrease the output slightly, from 32g to 31g, to compensate.

Over extraction is revealed as an ashy, smoky flavour that goes hand in hand with a lack of any lingering finish of the espresso in the mouth. When these flavours become apparent, we need to drop the grind back a touch coarser until they disappear.

Barista

Consistency and practice is the only way.
Credit: @repackespresso

Fine-tuning When Dialing In

At this point, I will start to adjust my brew ratio slightly. Higher brew ratios produce more viscous espresso, usually with lower extraction yields. Lower brew ratios extract more from the beans, but have a less prominent mouth feel. I favour the latter, as the higher extraction yields produce more complexity, especially through the interplay of the hard-to-extract burnt distillates and the more easily extracted fruit acids.

I’ll always try a lower brew ratio than my starting point of 50% but, as this increases extraction, I will usually adjust the grind slightly coarser. This means the extraction time is moderately shorter and I can ensure that I don’t over extract. Usually, I will go no lower than 40% (for example, a 16g input to produce a 40g espresso), as beyond this point the espresso becomes a little too thin for my tastes.

There are occasions during dialing in when I will increase the brew ratio to above 50%, but this only really happens when the beans are darker than I would like. Darker roasts increase the solubility of the beans, making them easier to extract, but, beyond a certain roast profile, they overpower the more delicate, complex flavours, meaning they often taste best when pulled quite short.

espresso

Balanced, complex and sweet.
Credit: @repackespresso

At the end of this process, we have an espresso that, hopefully, tastes complex, sweet, and well-balanced. Unfortunately, though, this is not the end; as the grinder temperature changes throughout the day, the flow rate of the espresso alters, meaning that adjustments need to be made to the grind fineness to keep the brew consistent. The reason for this is not, as commonly thought, the burrs moving as they become hotter and colder, but is related to the grind distribution changing at different temperatures. This is a subject for a separate post, though!

The Three Signs of Good Espresso

Espresso is a complicated beverage, and there is no one solution that provides the perfect outcome. The machine, the mineral content of the water used, and the grinder all influence its taste, and what works in one environment may not translate well to another. However, if you keep in mind the trio of balance, complexity, and sweetness when dialling in, you shouldn’t go too wrong.

Article edited by T.A.Jay

Perfect Daily Grind.