المهارات الاحترافية لإعداد الإسبريسو - (قيد الترجمة)

As baristas, we’re used to discussing grind size on a regular basis, adjusting the grinder to produce finer or coarser grinds throughout the day to keep to the shot time in our recipe as the grinder heats up or cools down. However, when grinders heat up, the aperture between the burrs doesn’t seem to be changing – which means the nominal grind size hasn’t actually changed. Instead, the grind size distribution has changed. Understanding the concept of grind size distribution is key to understanding some of the more recent developments in espresso making.

Listen to 2009 World Barista Champion Gwilym Davies narrate this lesson    Grinding is the process of applying stress to a material to break it up into smaller particles. Two…

Listen to 2009 World Barista Champion Gwilym Davies narrate this lesson  The grinder plays a critical role in the preparation of espresso. Compared with filter coffee, espresso is very strong…

The complexity of grind size distributions that we discussed in Lesson 1.03 explains why it is so difficult to replicate the desired grind size on different equipment. Even grinders of identical models at identical settings will produce slightly different grind size distributions, thanks to small differences in alignment or wear on the burrs, for example.

For this reason, replicating recipes across two different sets of equipment (for example, in two cafes in the same chain) is not always straightforward. Using the same numerical grind setting, even on two apparently identical grinders, will not produce the same results.

It’s possible to communicate a target grind size by using a proxy measurement such as shot time, but even this has limitations. For example, a particular espresso recipe using a Mahlkoenig EK43, a recipe that tastes great on a well-aligned grinder, might suffer from underextraction flavours or even be impossible to achieve on a grinder that is less well aligned.

  This video explains how to use the app. For those of you who prefer to read an explanation, we provide the written instructions below.   Prepare Your Grinds The…

The industry standard approach for measuring grind size distribution is to use a laser diffractometer. These machines cost hundreds of thousands of dollars, and so they are inaccessible to most…

Recap Extraction in espresso occurs only at the surface of particles  — this is called erosion This means a fine grind is required, and the smallest particles are especially important…

Photo of the Spirit espresso machine, kindly provided by Kees Van Der Westen. We explain how different machines control the water temperature and why some designs are more precise than…

The ‘exit temperature’ refers to the temperature at which brewing water leaves the group and hits the coffee. Different machines control this in different ways and, depending on the machine…

Multi-boiler machines allow the brewing water temperature to be set independently from the steam boiler. This allows more precise control of the brewing temperature and makes it much easier to…

Image: PID device used by Kees Van Der Westen. Early multi-boiler machines controlled the brewing temperature with a simple thermostat. It would activate the heating elements when the boiler temperature…

No matter what method the espresso machine uses to control the temperature, it’s important to be able to measure the exit temperature accurately in order to be able to calibrate…

While modern espresso machine designs are able to precisely control the temperature of the water leaving the group, this sadly doesn’t guarantee that all extractions take place at the same…

It’s well known that raising the brewing temperature increases extraction. There are two reasons for this: the first is that the molecules in hotter water are moving faster. This means…

As well as changing the total amount of each compound that can be dissolved (the solubility), the brew temperature also affects how fast each compound will dissolve. This is called…