Consistency is critical. Without it, espresso quality will fluctuate, recipes will be hard to refine, and returning customers looking for another one of those “amazing coffees” they drank last time will end up leaving disappointed.
Even small fluctuations in water, group head, and steaming temperatures can cause varying extraction yields and flavour profiles. Here’s why, and how to control them.
How Water and Group Temperature Affect Espresso Consistency and Flavour
We all know that the ideal temperature comes down to the beans’ solubility and that the lighter the beans are roasted, the less soluble they will become and therefore the higher the temperature we should use. However, it’s not as simple as it sounds.
The hotter the grinder, the higher the temperature of the ground coffee. This increases its solubility. Unless your grinder has temperature stability, like the Mythos 2, brewing temperatures should be decreased during peak periods to maintain consistent extraction yields.
What’s more, changing the water temperature affects the flow rate. During preinfusion, the coffee puck releases gases, mainly carbon dioxide. Some of these gases dissolve in the water, but bubbles are also created that block the water from passing through the puck, decreasing the flow rate.
Gases become less soluble at higher temperatures, which results in more bubbles, further decreasing the flow of water. The flow rate will then increase significantly during the rest of the brew time. This could be a result of channelling as the bubbles may cause small dry patches in the puck that water will bypass.
To avoid these issues, baristas need to pay careful attention not just to the brew recipe but how conditions are changing during the day. This will allow them to adjust the water temperature appropriately.
How Steam Temperature Improves Milk Consistency and Flavour
Small variations in steam temperature can have a big effect on the beverages that you’re serving. Milk that’s too cool will result in poor foam and latte art, while overheated milk will have a thinner, more watery consistency and a potentially disappointing mouthfeel.
The SCA recommends steaming milk to 55–65°C, but the ideal temperature will depend on the milk’s protein and fat content as well as your aim for the beverage. The higher the protein and the lower the fat, the easier it is to create foam at slightly lower temperatures – but the pay-off is a less creamy body.
A dual-boiler machine will mean you can keep the steam wand at a consistent temperature and pressure, ideally slightly lower than the group head. Our T3 technology will also make it easier to set the water, group, and steam temperatures at the individual group heads.
How to Improve Temperature Consistency in a CaféControl over the water and milk-steaming temperatures allows you to improve the consistency and flavour of your beverages, improving customer satisfaction and retention.
To achieve this:
1.Train your baristas so they understand the relationship between temperature, flow rate, flavour, and extraction; this will help them to make the right decisions in service.
2.Encourage staff to regularly record in a journal group, water, and steam wand temperatures, if they have access to this information, along with their thoughts on the brewed coffee’s flavour and milk. This will deepen their understanding of the topic.
3.Make things as simple as possible so your team can focus on customer service instead of temperature adjustments. Grinders such as the Mythos 2 offer temperature stability while our T3 technology gives the barista the power to set and maintain water, group head, and steam temperatures, creating consistency shot after shot.