How temperature stability can affect extraction

Effect of temperature on coffee extraction and taste

There are a large number of variables that are directly involved in coffee extraction. These include grind size, extraction yield, brew ratio, water temperature and others. Water is very important in extraction and must be kept between 92 °C and 98 °C depending on the coffee variety and roasting profile.

The maximum % of substances we can extract from coffee is 30%. However, such coffee is not drinkable.

And how did thetemperatures affect the taste? Cups of coffee with the lowest temperature have lower sweetness, bitterness but higher acidity. On the other hand, coffee with the highest temperature has a lot of sweetness, bitterness and medium acidity. The medium values are balanced with high sweetness and balanced acidity and low bitterness.

All assuming other espresso recipe variables are held constant. We do not adjust grind fineness, coffee dose or extraction length. Only the temperature of the water changes.

Does this have anything to do with the extraction yield of the coffee, or does it have something to do with removing some of the coffee components? The following chart and data based onresearch by Australian baristas proves both.

Theamount of citric acidextracted decreases as the temperature increases from 94°C to 100°C. The amount of malic acid in a cup of coffee is lowest at 94 °C. Sucrose/sugar extraction is optimised at 94 °C, with a large increase from 74 °C.

Why temperature stability is important for espresso extraction

Espresso is extracted in less time than filter coffee. It is a more concentrated beverage that requires a higher level of control over other extraction varia bles in addition to the requirement for finer grind size. Even the smallest fluctuations in temperature of water affect the preparation of espresso .

Espresso is a more concentrated beverage that is extracted over a shorter period of time. Source.

Mimicking the perfect extraction of espresso can be very difficult indeed. Pre-infusion of coffee means leaching the ground coffee through water and getting rid of undue amounts of carbon dioxide. Espresso will be more fragrant and tasty after the pre-infusion (blooming) process. I will describe the process below in a separate chapter.

How we can control the temperature during extraction

Coffee machine materials can significantly improve thermal stability. Stainless steel and brass absorb heat quickly and can hold it for longer periods of time. High-quality espresso machines usually have a higher level of thermal inertia just because of their design.

Technologyhas advanced significantlyover the years. Coffee machines are qualitatively different, which has naturally led to improved thermal stability in professional espresso machines.

If you want to observe changes in coffee extraction, you can no longer do withoutPID control (proportional integral derivative control). Increasingly ,E61 coffee machine heads, pre-infusion sensors and heat exchanger or dual boilers are required in home coffee machines for better thermal stability.

How the E61 head helps with temperature stability

Themachine head is probably the most underrated part of espresso machines. People tend to focus on the flashier stuff, and manufacturers tend to draw attention to other more "visible" features.

Itdelivers hot water at high pressure in an even manner through the shower head of the coffee maker. These can be seen when you disconnect the portafilter. However, only one coffee maker head can boast the glitzy title of best of all. This is the E61 coffee machine head.

The E61 head delivers hot water at high pressure in an even manner. Source.

The why of the E61 may be clear to you. The legendary Faema E61machine was a revolutionary espresso machine in 1961, the first machine to incorporate an electromagnetic pump. The head of this coffee machine began to perform several different functions that helped this machine create even better coffee.

The main goal of the E61's head is to maintain a stable temperature. This is achieved in two ways:

  • by increasing the overall density of the machine head - it uses a lot more material (metal) to hold the temperature longer.
  • Thermosiphoning - a mechanism that siphons water from the boiler into the coffee maker head and then circulates it directly back into the boiler. This is a continuous process where water enters and exits the head of the coffee maker.

Pre-infusion to promote coffee flowering

Coffee, like a flower , blooms into beauty and you need to provide the ideal conditions for it to do so. Pre-infusion (blooming) is a system we encounter both in home coffee machines and inmanual coffee preparation.

It is the process of leaching water through the ground coffee that sits in the portafilter It begins before the coffee is extracted. A very small amount of water is used to soak the coffee evenly in the portafilter . This is also done at a lower pressure and slightly higher temperature than that used for the extraction stage.

Pre-infusion protects against channeling. The aim is to allow the water to flow through the smallest possible area so that the coffee is not over-extracted. If the slightest space is created in the packed coffee, thechannel created will allow most of the water to flow through during extraction. The coffee will be too bitter and undrinkable.

The effect of the thermoblock on thermal stability

One thermoblock or two in the coffee machine? That's what it's all about, because you can also consider these two options when choosing a coffee machine . This water heating system is different from a heat exchanger and a boiler.

Will you choose a coffee machine with 1 or 2 thermoblocks? Source.

Single Thermoblock Coffee Maker

Acoffee maker with a thermoblock has an alternative way of heating the water. It is a heating element through which the water is passed to be heated. The main advantage is the lower purchase price and thanks to the electric thermostat you can achieve a stable temperature.

However, the disadvantage is poor water temperature control. Due to the flow rate, the spiral is not able to heat the water fast enough. The temperature can thereforefluctuate considerably during the extraction process. This can affect the taste of the resulting coffee.

Coffee machine with two thermoblocks

Thecoffee machine with two thermoblocks is ideal for lovers of lattes, cappuccinos and other milky coffee drinks. Therefore, there is no need to heat the coffee machine to the desired temperature to use steam. Otherwise, cool it down for espresso preparation.

Coffee makers supplied in conjunction with PIDcontrol provide us with extremely accurate temperatures when making coffee. However, you have to take into account that getting a coffee maker with two thermoblocks will be more expensive.

Ensure thermal stability by choosing the right coffee machine

You already know that you can influence the thermal stabilitybefore and during extraction. You need to pay attention to several criteria when choosing the right coffee machine . So be sure toask an expert to help you choose your new coffee machine. This way you can be sure that you have chosen the right home coffee machine.