Before we answer those important questions, let's start from the very beginning: why grind? In essence, it is the best method to increase the solubility of the bean. It allows us to, among other things, extract all the aromatic compounds of the coffee and offer a balanced, tasty and full-bodied cup.

In short, grinding is undoubtably something which cannot be ignored when it comes to correct extraction of the raw material.

Grind Adjustments

The time taken and the type of extraction are the key variables in the grind equation. The adjustment of the grind (granule size) in relation to time is in fact a key factor to consider in order to begin to have a greater understanding of the process.

Let's start with this idea: the shorter the extraction time the more it is necessary to have a finer grind, since there is less time to render the solids soluble in the cup. Espresso is a great example of this and the most suitable extraction method for this type of grinding as it requires a rapid process otherwise there is the risk of over-extraction, i.e. bringing too many solids into the cup, and therefore producing a bitter and harsh taste.

The opposite phenomenon, the one called under-extraction, will instead occur with too coarse a grind. This will reduce the contact time between coffee and water due to too little resistance being met by the water.

The extraction method is the other fundamental variable in the regulation of the granule size in the coffee.

The tool and technique that you decide to use will in fact have a decisive impact. The different extraction methods involve a different interaction between water and coffee: each method has its own characteristics and peculiarities through which times and techniques change, consequently each requires a different grind setting.

The most widespread methods today can be divided into three categories: pressurised (for example, the one used for the espresso coffee we drink at the bar or the moka at home), the percolation method, in which a large quantity of water passes through the coffee, and immersion or infusion, where the coffee is immersed in water for a long time before being filtered (not always) and drunk.

In the case of espresso then, given the high pressure of the water that comes into contact with the coffee (about 9 bar), in addition to correct grind, correct tamping will be important. A contact surface as flat and uniform as possible must be maintained to avoid preferential water flow, known in the industry as channelling.

Our advice? Play a little with the dose with respect to the final extraction time, adjusting the granulometry (coarseness, fineness) accordingly. Keep these numbers in mind as an initial guide:

Yes, we know, easier said than done! Let's take espresso coffee as an example:

Placing 15 grams of coffee in the filter holder will increase the coffee's resistance to water. If the extraction time is too short, reduce the granulometry (i.e. a finer grind).

If, on the other hand, the espresso takes 40 seconds or more it means that the measure of the ground coffee needs to increase (i.e. a courser grind).

We can also correct the dose if the portafilter’s basket allows us a bit of fine tuning.

Apply this method to other extraction systems as well and always taste the final result to understand how these parameters influence your extraction and consequently the organoleptic profile of the cup.

We actually talk more about the different coffee extraction methods here, if you want to learn more click here.

So, why is coffee freshness important?

So far we have talked about grinding, times and methods, so let's now see how and why coffee grinding is a process which demands fresh coffee. Freshness has always been a priority for those who understand it, or at least it should be.

The freshness of a raw material is what makes a product "high quality". Espresso enthusiasts – or even just those who love to enjoy a good coffee at the end of a good meal - know all too well that the freshness of the beans and ground coffee are essential for success in the cup.

A quality coffee can be recognized by various factors, from grinding to extraction, from colour to aroma; but the first variable element on which the quality of the coffee depends is certainly its freshness.

For this reason, grinding should be undertaken at the time of consumption, otherwise we risk losing more than half of the volatile compounds hidden in the bean, which are essential for giving complexity to the drink.

You would have noticed how much more intense the aromas are of a freshly ground coffee compared to a coffee that has been ground hours (let alone days) earlier, right? So be prepared - equip yourself with a manual or electric grinder.

Keepin’ it fresh: a how-to guide

As time passes, coffee beans gradually lose their aroma and taste, drying out producing a stale taste over time. The nuances and complexity of the coffee seriously risk being lost if the raw material is not well preserved.

There are several factors that affect the freshness of coffee after it has been roasted.

First of all, the humidity of the environment in which it is kept and the odours that surround it. Even light and heat can alter the freshness, in particular the bean’s internal oils which contain a large part of the aromatic compounds. Of all factors, however, the most dangerous risk is undoubtedly oxygen, or the surrounding air.

It is the number one enemy for coffee because it attacks the soluble aromatic compounds of the beans - even more so for ground coffee since it has an even more exposed surface, deteriorating each granule. This destructive chemical process is called oxidation, the same process that causes some metals to rust. Consequently, it is much, much better – and strongly recommended - to grind coffee on the spot and in small quantities.

Some advice on storing coffee to preserve its freshness over time:

• use resealable zip-up bags to avoid contact with light and gas

• store in a dry place, not in the refrigerator!