Espresso machine manufacturer Nuova Simonelli has shared advice on how baristas can control the temperature of their coffee to achieve better consistency.
Nuova Simonelli says 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.”
It adds even small fluctuations in water, group head, and steaming temperatures can cause varying extraction yields and flavour profiles.
How water and group temperature affect espresso consistency and flavour
Nuova Simonelli says the ideal temperature comes down to the beans’ solubility, and that the lighter the beans are roasted, the less soluble they will become. Therefore, the higher the temperature should be. However, it’s not that simple.
The hotter the grinder, the higher the temperature of the ground coffee. Nuova Simonelli says this increases its solubility. Unless the grinder has temperature stability, like the Mythos 2, brewing temperatures should be decreased during peak periods to maintain consistent extraction yields.
Also, changing the water temperature affects the flow rate. During pre-infusion, 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.
Nuova Simonelli says 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, Nuova Simonelli says 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, Nuova Simonelli says. 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 Specialty Coffee Association recommends steaming milk to 55 to 65°C, but the ideal temperature will depend on the milk’s protein and fat content as well as the barista’s 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 Nuova Simonelli says the pay-off is a less creamy body.
A dual-boiler machine will keep the steam wand at a consistent temperature and pressure, ideally slightly lower than the group head. Nuova Simonelli says its 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 café
Control over the water and milk-steaming temperatures allows baristas and café owners to improve the consistency and flavour of their beverages, improving customer satisfaction and retention.
To achieve this, Nuova Simonelli recommends:
- Training baristas so they understand the relationship between temperature, flow rate, flavour, and extraction. It says this will help them to make the right decisions in service.
- Encouraging staff to regularly record group, water, and steam wand temperatures in a journal if they have access to this information, along with their thoughts on the brewed coffee’s flavour and milk. The manufacturer says this will deepen their understanding of the topic.
- Making things as simple as possible, so the team can focus on customer service instead of temperature adjustments. Nuova Simonelli says grinders such as the Mythos 2 offer temperature stability while its T3 technology gives the barista the power to set and maintain water, group head, and steam temperatures, creating consistency shot after shot.
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