An expansion on our previous topic of calibrating an espresso extraction, we look at the knowledge involved in taking an espresso and ensuring that it can also come forth in the milk format.

The main idea behind contemplating the balance between coffee and milk is the concept of the total amount of coffee compounds found in an espresso.

A perspective that is less taken in coffee, the total amount of coffee compounds found in a coffee measures the gross amount of coffee compounds found in the cup of coffee that we drink.

To calculate this, we use the equation:

Total Amount of Coffee Compounds (g) = Brewed Coffee (ml) x TDS (mg/l)

To actually make an espresso that ‘cuts’ through milk such that one can taste the coffee that is present in a fixed volume of milk, we require sufficient coffee compounds in the extracted espresso in order to have the coffee sufficiently perceptible in the milk beverage.

Many factors come into play in determining what this sufficient amount is for a white coffee. The choice of coffee, its roast level, as well as café and barista preferences all matter, and in turn, the amount of coffee compounds to be considered sufficient varies largely.

Prior to calibrating a coffee for milk formats, it is first important to go through the thought process of considering the vessel and coffee-to-milk ratio.

With this in mind, the actual calibration of an espresso extraction to account for milk beverages is relatively straightforward – the only choices to make are between increasing or decreasing the overall amount of coffee compounds.

The overall amount of coffee compounds extracted can be changed in various ways, all producing an equivalent result. Be it increasing the output yield, the input dose of coffee, extraction, or even grinding finer – all of them work in some way to increase coffee compounds extracted in the final espresso.

However, deciding the appropriate change to make is difficult. Often, while a coffee may indeed cut through milk after adjusting the brewing parameters, it also becomes an imbalanced cup of espresso.

The common conundrum we will therefore need to get around is the balance between a tasty and well-rounded espresso while also having sufficient coffee compounds to be tasted through milk.

As such, calibrating for milk balance is not so much a separate activity from the calibration of espresso extraction, as much as it is an incremental process from the latter.

Deciding which variables to change (grind size, output volume, coffee dose, brewing temperature) to increase total amount of coffee compounds extracted really depends on the taste of the current espresso, and identifying potential changes or improvements that will still retain a good balance and taste profile within the espresso.

From our previous journal on espresso extraction parameters, grind size affects the strength, viscosity and texture of the espresso. A commonly adjusted extraction parameter, it is important to reassess an espresso after changing the grind size of the espresso extraction.

On the other hand, coffee doses (usually done in ±0.5g margins) affects the intensity and roughness in the flavour profile. Avoid changing the dose by large proportions, as it will increasingly alter the extracted espresso as a whole.

Lastly, temperature and output volume impact the balance of the espresso and desired intensity, while influencing the taste progression of the espresso.

The first anecdotal incidence of milk being added to a coffee beverage was in 1660 by Johan Nieuhof, Dutch ambassador to China. In the years since then, it has grown to become accepted as a mainstay in the coffee world today.

To be a competent modern barista requires us to be able to produce excellent coffee in all formats: hot and cold, black and white, alike.