These are steam-driven machines that produce very strong coffee. Espresso coffee is much richer and more concentrated than filter coffee and is the base for a cappuccino or latte. There are two basic types of machines, with pump machines the more expensive.
Similar to a radiator in a car, water is boiled in a chamber and this builds pressure and steam. Eventually enough pressure is built up and forces the boiling water through to the coffee. The steam can be used for frothing. The disadvantage is that the water is too hot to make an authentic espresso and often the bar pressure is not enough to make a really good espresso.
More expensive than pressure machines, pump machines have a separate tank and a thermostatically-controlled boiler with a 'Thermoblock' system that heats up the water to between 85-92°C - the optimum temperature for making coffee. The water is then sent through the coffee holder at the correct bar pressure.
Espresso coffee is made by using finely-ground coffee. Some machines also use a pod system and many now use the increasingly popular Nespresso method.
This is also a 'pod' system that produces espresso coffee. The coffee is blended, roasted, grounded, and then hermetically sealed in capsules which stay fresh for up to 9 months. The advantages of this system are that it's an easy way to make coffee, and most major brands of coffee makers have Nespresso systems. There are no messy filter holders to clean, no spillage of coffee granules - and the coffee tastes great! The downside is that you are tied to the supplier's range of coffees, which are at present only available by mail order.
Points to consider when buying an espresso maker
Good bar pressure is essential for making a good 'crema'. It means that the steam meets the coffee granules at the correct speed. Too slow and it could result in a bitter taste. 15 - 19 bar is the optimum, though some suppliers claim 9-11 bar is enough if the beans have been ground correctly.
Rather like a shower, the Thermoblock is a type of boiler that heats up the water to about 90°C, via a pump. To achieve an excellent flavour it's important that you don't scald the coffee - unlike tea. Some models have a Thermoblock system for frothing the milk, which needs to be at about 120°C.
This holds the coffee granules and should be kept warm. Basic models have aluminium ones but more expensive models have brass holders that retain the heat for longer.
Most machines have a mechanical valve to control the water flow. Top-of-the-range machines have solenoid valves that increase the water pressure at the point of delivery and also shut off as soon as you finish the extraction
Like kettles, the higher the wattage the faster the water is boiled. High wattage machines are good if you are making several espressos.
Tips on making a perfect espresso or cappuccino
If you want to imitate the 'baristas' of the Italian coffee bars (experts in the art of making an espresso) it is essential you know how to achieve a perfect 'crema'.
Crema is the pure coffee extract you find on the top of an espresso. Resembling the head you'd find on a glass of stout, it's full of rich aroma and leaves a lingering flavour. A test of a good 'crema' is to put a little sugar on the top. If it takes time to fall to the bottom you've succeeded!
Types of coffee
- Cappuccino: 1/3 espresso, 1/3 hot milk, 1/3 frothy milk
- Latte: with added hot milk. Normally ratio is 1:6 espresso: hot milk.
- Macchiato: espresso with a little touch of milk
- Con Panne: espresso with a dash of cream
- Mocha: hot chocolate with a dash of espresso
- Americano: hot water with a dash of espresso
For perfect frothing you can use any type of milk - full cream, semi-skimmed or skimmed is fine - as long as it's fresh. It's the protein that makes the froth, and this diminishes after about 4 days. Always use a stainless-steel jug (it conducts heat better) and fill it to just under half full with cold milk. When it's too hot to touch at the base the froth is ready. Give it a couple of taps to get rid of any bubbles, and then gently spoon the froth onto your espresso for that perfect cappuccino!
The Coffee Machine Guide
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