PART 3

Espresso Processes: Dosing, Tamping and Waste

As instructed in the previous section (and in both Foundation and Intermediate) the SCA Barista Skills Program has provided standards with expectations for accuracy in dosing, tamping and minimizing waste. These same standards will be held as you continue to advance your theoretical and practical skills at the Professional level.

You should recognize inconsistencies in dosing and tamping when you are preparing a drink. Can you quickly spot the fluctuation of espresso flow and predict the impact upon extraction? Taking that knowledge will you be able to quickly self-correct to bring your espresso back into recipe standards?

While preparing espresso based drinks, waste can accumulate in several areas. You should recognize where waste occurs in espresso production, milk preparation and service. Some waste may be inevitable, but how much is acceptable is the foray of the Barista Skills Professional. If you are unclear about these expectations from prior modules you may refer to the Practical Exam and Exercises at the end of this course.

A good practice for you as you prepare for your exam is the measure espresso ground waste in 0.5g increments. For example can you prepare 4 espresso beverages with waste measurement under 5.0g coffee grounds? Or do you waste 5.0g per espresso beverage? The accumulation and cost of waste can further calculated.

In addition to waste, there is the accumulation of water, grounds and milk which may spill around the grinder, espresso machine, knock box and service area. This spill and mess is to be controlled during your practice and your examination so that a tidy workplace may be observed by your examiner.

Grind Particle Distribution

Different espresso grinders will produce different quality espresso grounds. The intention is not to say that one brand of grinder is better than another, but rather to inform learners that each shall understand the style of grind produced by their grinder and burr set. All grinders must be maintained in proper working order, cleaned and with sharp burrs. All grinders must avoid creating heat in the grounds and should be free of obstructions to ensure consistent well distributed espresso grounds.

The focus of this section is grind particle distribution. Specifically the ratio of larger pieces blended with small pieces of espresso grounds. It is worth reminding that particle distribution in espresso is a good thing. Larger particles allow some water to flow through tightly packed espresso baskets, while the smaller particles created resistance and balance the flow of water.

Impacts of particle distribution in a portafilter basket:

• If an espresso grinder produced only consistent coarse grounds the water would easily pass through and create channels resulting in under- or uneven-extraction.
• If an espresso grinder produced only consistent fine grounds the water would be obstructed, not able to pass through and cause over-extraction.
• It is the proper mixture of particle sizes which helps create uniform flow, prevent channelling and encourage proper extraction.
• Too great a distribution in size is NOT desired. If there are too large and too small pieces blended in the basket the large will not be able to extract while those too-small will over extract. This causes unpleasant and uneven extraction.

The most suitable range of espresso grounds is 250-450 microns.

Much like green coffee grading (sizing) sieves/screens we will place a sample of ground coffee on top of a stack of sieves and shake it down. This filters the grounds from larger (top) sieves to the smaller (bottom) sieves. We then estimate the size of grounds by the sieve it rests upon. The proportion of the original sample can then be calculated to find our distribution.

It should also be noted that the word "distribution" implies that there is an even mixture from top to bottom, left to right, of each particle size. This is one reason that tapping or hitting sides of the portafilter basket is discouraged. By hitting the portafilter smaller grounds naturally fall to the bottom while larger particles settle to the top... and of course we may push grounds to the direction in which we strike the basket.

CAUTION!

This is NOT the case with brewed coffee grinders, which seek uniformity in grind size to allow to uniformity in extraction. There are several variables which cause uniformity or variability in grind particle size distribution including:

• The motor speed of grinder - faster motors produce faster grinds, but may lead to variability in particle size with some heating to the grounds. Slower motors then are often preferred to assist with consistency and to avoid heating the grounds.
• Burr size - smaller burrs possess less surface area for grinding coffee. This requires more time and more spinning revolutions to grind coffee. More time and spinning can create more heat. Thus lower speeds or larger burrs are preferred.
• Burr blade design - how the teeth are situated, larger or smaller teeth and positioning will impact the variability of grind particle size.
• Bean temperature - cooler beans should grind slower and break/chip less easily.
• Roast degree of beans - darker roasts grind more easily and may have fragile edges that break and pass through quickly. Lighter roasts (similar to cooler beans) requires more energy and results in a more narrow particle size distribution.

Nice work! Keep it up.