The Professional Barista’s Handbook The Professional …

 

 

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The
Professional
Barista’s
Handbook

An Expert’s Guide to Preparing
Espresso, Coffee, and Tea

Scott Rao

Contents

Introduction xi

1. Getting Started 1

2. Espresso 3
Espresso Percolation: a Primer
Grinding for Espresso
Dosing and Distribution
Grooming
Tamping
Water Temperature
Putting It All Together
Preinfusion
Espresso-Making Techniques in Italy Versus America
Pressure Interruptions During Espresso Brewing

3. The Science and Theory of Percolation and Extraction 35
Percolation Dynamics
Fines
Basket Shape and Extraction
Espresso Brewing Ratios and Standards

4. Milk 45
Milk Steaming
Milk Pouring

5. Barista Systems 61
Efficiency Enhancement Tools
Workflow

6. Drip Coffee 67
Freshness
Drip Brewing Standards
Grinding
Temperature
Turbulence

Optimizing Different Batch Sizes
Coffee Brewing Chart
Setting Up the Filter
Stirring: the Key to Making the Best Drip Coffee
Programmable Brewer Settings
How to Hold Brewed Coffee
Brewing Drip Coffee to Order
Coffee Filter Types
Freezing Coffee Beans

7. French Press Coffee 79
How to Make Great French Press Coffee

8. Water 81
Water Chemistry 101
Brewing Water Standards
Water Treatment
Descaling

9. Tea 87
Basic Tea-Making Guidelines
Preparation by Tea Type

Appendix 91

References 93

Glossary 95

Index 99

Introduction

When I began in the coffee business fourteen years ago, I read every book I could
find about coffee. After reading all of those books, however, I felt as if I hadn’t
learned much about how to make great coffee. My coffee library was chock-full of
colorful descriptions of brewing styles, growing regions, and recipes, with a few
almost-unreadable scientific books mixed in. I would have traded in all of those
books for one serious, practical book with relevant information about making great
coffee in a café.

Fourteen years later, I still haven’t found that book. I know many other profes-
sionals as well as some obsessive nonprofessionals would like to find that same
book I’ve been looking for. This book is my attempt to give it to them.

Chapter Title

xi

The Basics
Espresso is produced by the percolation of pressurized hot water through a tightly
packed bed of finely ground coffee. The water erodes solids and oils from the sur-
faces of the coffee particles as it flows through the coffee bed and deposits the solids
and oils in the cup.

The flow rate of the water through the grounds is determined primarily by the
amount of pressure applied by the machine, the mass of the grounds, and the fine-
ness of the grind. Higher pressure, up to a point, increases the flow rate; beyond
that pressure, flow rate decreases. A larger dose or a finer grind produce greater
flow resistance and a slower flow rate.

Water always follows the path of least resistance through the coffee bed; it is
the barista’s job to create not only the proper amount of flow resistance, but also to
form the coffee bed such that it provides uniform resistance to the water. A poorly
formed coffee bed is vulnerable to the creation of a channel, an area of high-velocity
flow through the coffee bed.

Channels are detrimental to brew strength and flavor. The large volume of water
flowing through a channel dilutes the shot and causes the grounds along the chan-
nel to overextract,* increasing bitterness. Because less water passes through the
denser areas of the coffee bed, those areas underextract,* resulting in underdevel-
oped flavors and lower brew strength. To minimize channeling, a barista should
prepare a bed of grounds so it has a smooth and level surface, forms a tight seal with
the wall of the portafilter basket, and is of uniform density.

Evidence of channeling can sometimes, but not always, be seen when using a
bottomless portafilter. Channeling is indicated when extract flows more rapidly or
yellows more quickly from some areas of the basket than others.

The Barista’s Role
When preparing an espresso, a barista’s basic goals should be to:

• Create a dose of consistent mass every shot.
• Choose the grind setting that will provide the desired flow resistance.
• Distribute the dose evenly to provide uniform resistance to the water.
• Tamp with enough pressure to eliminate void spaces within the coffee bed and

to seal the surface of the bed.

• Ensure the brewing water is of the desired temperature.
• Complete all of these tasks efficiently.

The Grinder’s Role
The grinder is the most important piece of equipment in an espresso bar. Grind-
ers are usually overshadowed by more expensive, flashier espresso machines, but

* The terms “overextract” and “underextract” are subjective; by using them I do not mean to imply
there is a universally agreed-upon ideal level of extraction for coffee, tea, or espresso. Instead, the
reader should interpret overextraction as a general reference to extracting more than the intended
amount, usually to the point of excessive bitterness or astringency. Underextraction is meant to
indicate less extraction than intended, usually such that the resulting beverage has insufficient
flavor development.

The yellow extract on the left indicates channeling.

grinder quality is arguably the single most important factor in preparing a great
espresso.

A quality grinder must:
• Produce the proper particle sizes to provide adequate flow resistance.
• Create a bimodal or trimodal distribution of particle sizes. (See “Grinding for

Espresso” in Chapter 2.)

• Cause minimal heating of the grounds during grinding.
• Limit the production of fines.

Fines play many important roles in espresso percolation; these will be discussed
in detail in Chapter 3. For now it is important to know that the brewing water can
transport and deposit fines lower in the coffee bed during percolation, a phenom-
enon known as fines migration. When fines and large insoluble protein molecules
are deposited at the bottom of the coffee bed they can form a compact layer,1 or
densely packed solid mass. A compact layer clogs holes at the bottom of the filter
basket and can result in obstruction of flow paths, uneven resistance to flow, and
channeling. It is desirable to have some fines, but too many fines or too much fines
migration can damage espresso quality.

The Espresso Machine’s Role
The espresso machine’s task is to deliver water to the grounds in a predetermined
pattern of temperatures and pressures. These patterns are known as temperature
profiles and pressure profiles.

A quality espresso machine should be able to produce consistent temperature

and pressure profiles every shot, even under heavy use.

4

Espresso

Espresso

5

The Dynamics of espresso percolaTion anD exTracTion

According to the research done with large percolator columns, diffusion does

Key
Extract
Fines
Water
Channel

DRY
T=-10 seconds

LOW PRESSURE WETTING
T=-1 second

not occur until coffee particles are:

1. “Satisfied with bound water.” Coffee particles can hold up to about 15% of

their dry weight as bound water.16
2. Saturated with free extracting liquid.7
3. Free of gases.7

The typical espresso extraction time is probably too short for all three precondi-
tions of diffusion to be met. Therefore, it is likely that espresso extraction is accom-
plished entirely by the washing of solids from the outer surfaces of coffee particles,
as well as by the emulsification* of oils.9 Diffusion plays little, if any role.

FULL PRESSURE & FIRST EXTRACT
T=0 seconds

BEGINNING OF EXTRACTION
T=5 seconds

MID-EXTRACTION
T=15 seconds

LATE EXTRACTION
T=25 seconds

The color of the grounds (represented by the stacked rectangles) in the first frame is deep red,
indicating they are concentrated with coffee solids. The lighter reds in later frames represent
lower solids concentrations.

T = -10 seconds: The dry grounds just before the pump is engaged. The grounds are packed
with solids, and fines are scattered throughout the coffee bed.

T = -1 second: The coffee bed near the end of preinfusion. The water has percolated through
almost all of the coffee bed but extraction has not yet begun. The grounds have absorbed
water, swelling the coffee bed. A channel, represented by the yellow line, has formed through
the middle of the coffee bed. The upper layers of the coffee bed have lost solids, while the
lower coffee bed has gained solids. Fines have begun to migrate down the coffee bed.

T = 0 seconds: The first extract appears. The first extract appears at the outlet of the channel.
Fines and solids have concentrated in the lower layers of the coffee bed. The coffee bed con-
tracts as pressure increases.

T = 5 seconds: Early extraction. Solids and fines are rapidly removed from the coffee bed. The
coffee bed is further compressed as full pump pressure is applied.

T = 15 seconds: Mid-extraction. The coffee bed shrinks as it loses mass. The upper layers of
the bed are almost depleted of extractable solids. The bulk of fines and solids are concentrated
in the lowest layers of the bed.

T = 25 seconds: Final moments of extraction: The upper layers of the bed are completely empty
of extractable solids. The coffee bed has lost about 20% of its original dry mass.

Flow Progression
The initial extract from the flow of a well-prepared shot should be viscous and
dark.‡ As the flow progresses the extract becomes more dilute and the color grad-
ually lightens, eventually turning yellow. Cutting off the flow when it yellows, or

* The emulsification of oils seems to be enabled by the pressure of espresso brewing. It is arguable
that the emulsion is the aspect of an espresso most responsible for differentiating it from a very
concentrated cup of coffee.

‡ The color of the extract is believed to be darker when it has a higher concentration of caramelized
solids or a lower concentration of CO2, though there may be other factors that influence color.

38

The Science and Theory of Percolation and Extraction

The Science and Theory of Percolation and Extraction

39

How to Pour Latte Art
To pour latte art you must have a fresh shot of espresso with a reasonable amount
of crema and properly textured steamed milk. The milk should look creamy and
glassy, with no visible bubbles.

The most common mistakes beginners make are pouring the milk too slowly
and lifting the pitcher away from the surface of the beverage while pouring. Pouring
milk too slowly can cause it to separate in the pitcher, causing less-aerated milk to
pour into the beverage and more-aerated milk to remain in the pitcher. This makes
pouring latte art difficult and also results in an under-aerated beverage. Raising
the pitcher away from the surface of the beverage causes the milk to dive under the
crema rather than resting on top of the crema and forming a design.

Raising the pitcher while pouring prevents the milk from resting on the crema because
the flow of the milk is accelerated by gravity. Raising the pitcher is analogous to diving
from a high board: just as the milk dives to the bottom of the cup and hardly disturbs
the crema, the diver cuts through the surface of the water with hardly a ripple and
submerges deeply. On the other hand, pouring with the spout of the pitcher kept very
close to the surface of the beverage is analogous to diving from the edge of a pool:
the milk skims the surface of the beverage just as the diver merely skims the surface
of the water.

The Spoon Method
The spoon method is common in New Zealand, but I’ve yet to see it practiced else-
where. The benefits of the spoon method include delaying froth separation in the
cup and allowing control over the texture of the milk while pouring. The disadvan-
tages of the spoon method are it takes more time than free-pouring, requires the
use of both hands, and is harder to master.

The spoon method works best with a round bell or vev pitcher with a beveled
edge. The wide mouth of the bell pitcher provides a better view of the milk texture
while pouring and allows easier spoon access and control.

To execute the spoon method, steam the milk, groom it if necessary, and use a
tablespoon as a gate to control the flow and texture of the milk as it is poured. The
details are different for each drink, but the basics are the same.

1. Begin the pour with the spoon tightly restricting all but the densest, least
frothy milk. Some baristi use the spoon to pull back (away from the pouring
edge) the frothiest milk several times before restricting the milk and start-
ing the pour.

2. Pour into the center of the espresso at a moderate rate to prevent breaking

3. While pouring, lift the spoon slowly to allow frothier milk into the cup.
4. The surface of the finished drink should be glassy and can be finished with

up the crema.

a design if desired.

Begin by pouring the milk
into the center of the crema.
Pour quickly enough to
prevent separation in the
pitcher but slowly enough to
keep the crema intact.

Maintain a consistent,
moderate flow rate through-
out the entire pour. To do
this, you must accelerate the
tipping motion of the pitcher
as the amount of milk in the
pitcher decreases.

Rock the pitcher back and
forth once the white cloud
appears.

Continue rocking the pitcher
to create a zigzag pattern. It
is critical to resist the urge to
raise the pitcher away from
the surface of the beverage.
It may be counterintuitive,
but keep the pitcher as low
as possible while pouring
and constantly accelerate
the tipping of the pitcher to
maintain the flow rate.

Ecco!

Back the pitcher toward the
edge of the cup while zig-
zagging. Once you reach
the edge of the cup lift the
pitcher a couple of inches
and drizzle a small stream
of milk back across the cen-
terline of the zigzags.

50

Milk

Milk

51

How to Milk-Share

Transfer about 1⁄3 of the milk from the large pitcher
to the small pitcher.

Spin the large pitcher to check the milk texture be-
fore pouring.

Combine remaining milk in the small pitcher.

Spin the milk in the small pitcher. Groom if
necessary.

Free-pour the cappuccino milk using the large pitcher.

Pour the café latte.

56

Milk

Milk

57

The Basics
It is common knowledge that brewing water should be carbon filtered and have no
“off” flavors. But that is only the starting point for quality brewing water. To get the
most out of your coffee (or tea or espresso), the water needs to have a neutral pH
and appropriate levels of hardness, alkalinity, and total dissolved solids (TDS).

The following water chemistry terms are relevant to coffee making.

Total Dissolved Solids (TDS): The combined content of all substances
smaller than 2 microns in any dimension dispersed in a volume of water. Mea-
sured in mg/L or ppm.

Hardness: Primarily a measure of dissolved calcium and magnesium ions,
though other minerals can contribute. Measured in mg/L or grains per gallon.

pH: A measure of acidity derived from the concentration of hydrogen ions; 7.0
is neutral.

Acid: A solution with pH lower than 7.0.

Alkaline: A solution with pH greater than 7.0.

Alkalinity: A solution’s ability to buffer acids. Measured in mg/L.

The terms and measurement units used to describe water chemistry often seem
designed to confuse. For simplicity I have left out numerous alternative units of
measurement and will measure TDS, hardness, and alkalinity in mg/L (milligrams
per liter, or parts per million).

A solution can be very alkaline but have low alkalinity, and vice versa. As an analogy,
think of alkaline as the solution’s location on the political spectrum. Let’s say alkaline
refers to being on the right, and acid refers to the left; alkaline denotes being con-
servative, acid denotes liberal. (No political commentary intended!) Alkalinity, on the
other hand, is analogous to stubbornness and resistance to becoming more liberal. Of
course, one can be at either end of the spectrum (acid or alkaline) and still be resistant
(have high alkalinity) or amenable (low alkalinity) to becoming more liberal.

Terminology
The terms alkalinity and alkaline do not refer to the same thing. “Alkaline” refers
specifically to a solution with a pH between 7.01 and 14. “Alkalinity” refers spe-
cifically to a solution’s ability to buffer an acid or, less technically, its resistance to
becoming more acidic.

The relationship between hardness and alkalinity also needs clarification. Hard-
ness is derived from calcium, magnesium, and other cations (positively charged
ions). Alkalinity is derived from carbonate, bicarbonate, and other anions (nega-
tively charged ions). A compound such as calcium carbonate contributes to both
hardness and alkalinity, because it has calcium (hardness) and carbonate (alkalin-
ity). On the other hand, sodium bicarbonate contributes to alkalinity but not hard-

ness. Common water softeners work by replacing the water’s calcium with sodium.
This decreases hardness but does not affect alkalinity.

Boiler scale is caused by the precipitation of calcium carbonate when hard water
is heated. Precipitation of scale decreases the hardness and alkalinity of water. Over
the long term, scaling can seriously damage your espresso machine. In the short
term, scaling can quickly clog small valves and passageways; gicleurs and heat ex-
changer restrictors are particularly vulnerable.

Espresso machine manufacturers routinely recommend using water softeners
to protect espresso machines. A softener will protect your machine but might ruin
your espresso. (See “Water Treatment Options” later in this chapter.)

Brewing Water Standards

I recommend the following water standards for brewing coffee, tea, and espresso.

WATER FOR COFFEE, TEA, AND ESPRESSO

TDS

120-130 ppm (mg/L)

PH

7.0

HARDNESS

70-80 mg/L

ALKALINITY

50 mg/L

Most industry recommendations call for slightly higher levels of hardness and
TDS than listed above; using those industry standards yields marginally better cof-
fee, but I cannot recommend them for espresso because they increase the risk of
scale formation.

In theory, water with hardness a little greater than 80 mg/L will not create scale
at typical espresso brewing water temperatures. In reality, machine temperatures
and the hardness yielded by water treatment systems fluctuate, and I’d rather err
on the side of caution. Caution is especially important when using gicleurs or heat
exchanger restrictors. Small amounts of scale can dramatically alter the perfor-
mance of these tiny orifices.

Please note: Hardness of 70 mg/L will create scale at typical steam boiler tem-
peratures. The only way to protect the boiler and still have great brewing water
is to install two separate lines with water of different hardness levels feeding the
espresso machine.

How Water Chemistry Influences Coffee Flavor
To put it simply, the less “stuff” already dissolved in brewing water, the more “stuff”
the water will dissolve from the grounds. If TDS levels are too high, water is a weaker
solvent and will not extract enough solubles from the grounds. Coffee brewed with
very high TDS water will taste dull and cloudy. Very low TDS water can produce
coffee with edgy, unrefined flavors and, often, exaggerated brightness.

Hard water does not decrease the potential quality of coffee or espresso; even
if the water feeding the coffee machines is very hard, the actual brewing water will
not be too hard because much of the hardness precipitates as scale at typical brew-
ing temperatures. Unfortunately, the scale can damage or alter the performance of

82

Water

Water

83