August 03, 2014

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How are ‘pro-sumer’ espresso machines different to what you can buy on the high street?

'Pro-sumer' is the coffee industry term for home espresso equipment that is of a professional / commercial standard.

We often get asked, 'What’s the big deal about your espresso machines?' and, 'How are they any different to the ones you can buy on the high street?'

So we thought we’d try to sum up the many ways in which they differ without getting too technical or nerdy! Let us know if you have any comments or questions below.

Temperature stability

Temperature stability is the key element to pulling solid, consistent shots of that sweet nectar. Why is this so important? Coffee solids need to extract evenly in order to give a balanced espresso. The temperature of the water determines the rate at which solids will extract from ground coffee – the hotter the water, the more solids will be washed from the coffee grounds. 

Why high street machines don’t deliver temperature stability

In single boiler machines like the Gaggia Classic, Rancilio Silvia, and Dualit, Delonghi, and Kitchenaid brands, the boiler uses two thermostats to control water temperature. 

 

This forces users to employ a technique called ‘temperature surfing’, whereby you flush water through the boiler to engage the heating cycle and once the boiler is at the ideal temperature, pull your shot. Finding the right spot to pull the shot can be a laborious process of trial and error using a stopwatch to guess at what point the boiler reaches x degrees.

As your espresso is pouring, the hot water leaving the boiler is being replaced by cold water from the reservoir, giving you an ever-declining temperature profile. This means the start of your shot could be over extracted (water too hot), the middle of the shot could be well extracted (water is the correct temperature) but as the shot reaches its end it becomes under extracted (water too cool), giving a very imbalanced espresso – and losing the great taste.

Some cheaper machines don’t use boilers but instead cheap ‘thermoblocks’ which heat water very quickly as it passes through – but again, they don’t hold water at the correct temperature.

How ‘pro-sumer’ machines achieve temperature stability

  • They use the famous E61 group head, which has water circulating between it and the boiler constantly in order to maintain a stable brew temperature. 
  • High grade brass and copper internal components retain heat.
  • Two boilers – dual boiler machines have one boiler for steaming milk and another for brewing espresso, which means you can do both things at the same time at unique temperatures.
  • One boiler – Heat Exchanger (HX) machines have one boiler but still achieve stable temperatures for steam and brewing. They do this by:
    • Superheating the boiler water to around 125°C, meaning there is always steam available for your milk. 
    • Passing the water for your espresso through a heat exchange tube in the middle of the boiler before passing it through a thermosyphon to arrive at the group head at around 94°C. 
  • A PID (digital temperature controller) control can allow you to control the water temperature (of the brew boiler in dual boiler machines). It gives much more precision and reduces the deadband ‘swing’ from high to low, to a consistently high range. 

Build quality

High street machines usually have a stainless steel case which contains many plastic, and often ill-fitting parts such as their driptrays, water reservoirs, and steam knobs. These generally feel flimsy and are not designed to stand the test of time.

Companies such as Expobar and Rocket finish their machines in high grade stainless steel which is on a par with commercial machines. Because they are produced by these commercial manufacturers they are constructed in a way that makes them highly durable. They also have a polished chrome finish, which admittedly is more about aesthetics than temperature stability – but hey, these machines are the Rolls Royce of domestic coffee equipment, so we’d expect no less.

So which machine is best for you?

The only way to pull shots that properly highlight the rich, sweet flavours of espresso at home, is by investing in a pro-sumer machine and good quality grinder.

That’s not to say small single boiler machines don’t have their merits, just keep in mind that while some of them can pull okay shots, they don’t provide the quality or consistency of their pricier cousins.

Find out more in our guide to buying domestic espresso machines

 


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