The perfect extraction time for an espresso is 25 – 30 seconds. This is true for pressurised and non-pressurised baskets.
The brew ratio we'll follow today is 20g of ground coffee to 30g of liquid espresso. Time ties everything together - the total number of seconds a shot takes. Aim for your shot to pull between 25 and 30 seconds.
The Operating Pump Pressure Is Wrong
If your operating pump pressure is set too low, your coffee will dispense too slowly—or sometimes it won't dispense at all. The optimal pressure is considered to be around 7 to 9 bars, so make sure you check the needle on your gauge before brewing to see if the setting is right.
Espresso coffee should be ground to a size in which the extraction process takes 28-30 seconds to yield 1.5-2 ounces of liquid. It is important to only adjust the grind and not the pressure one tamps with to control the flow rate.
It takes 10 seconds for an espresso shot to “go bad”. That is, for the heart, body and crema to blend together into a big black bitter mess. If you're drinking espresso straight, it doesn't matter.
A double shot of espresso should produce 60mls in 25 seconds. If the coffee comes through too fast, try to grind your coffee finer. If it comes through too slow, grind your coffee a little more coarse and try again.
Increase the wet dose if your shot is too concentrated or if it tastes under extracted. By letting the shot pull longer to increase the yield, you allow the grounds and water to be in contact for longer, which leads to more extraction. Adding 2-4 grams of yield is enough to make a very noticeable difference taste-wise.
Apply 20-30 pounds of pressure, and polish
Baristas often recommend 30 pounds of pressure, but some do as little as 20 pounds. More and more are finding that tamping pressure is overrated—it's hard on the wrist and cause an over-extracted, bitter brew. Use a twisting motion as you pull up to “polish” the puck.
Use only the freshest coffee beans. Grind coffee only as you need it. Brewing time for a single or double shot should be 20-30 seconds.
If you pull your shot too long or too short it will be out of balance. How do you know when to stop? The conventional answer is that you do it when the shot “blonds” turning from brown to blond. The exact point is hard to identify and is in some sense a matter of taste.
It will have a burnt, ashy flavor and may be less palatable than fresh shots; however, they still contain caffeine. The length of time it takes for a shot to 'die' is debated, ranging from ten seconds to three minutes.
The flow rate of an espresso machine is a measurement of how much water passes through the grouphead while the pump is active. Most commercial machines have a flow rate of between 250 and 500 grams per 30 seconds (g/30s), but the ideal range is between 200 and 280 g/30s.
For example, a 20-gram dose at 1:2 would yield a 40-gram double espresso. 18 grams in, yields 36 grams out. 25 grams in, 50 grams out etc. Simply multiply your dose by 2.
Typically, modern espresso is brewed around a 1:2 ratio, meaning that if you start with 20g of ground coffee in your basket you should aim for something like 40g of brewed espresso in your cup.
There are two main reasons there's no flow coming from your group: a clog or a faulty brew valve. Have you been experiencing anything abnormal before the flow stopped? Low flow would likely indicate a clog, while strange noises would be more indicative of a faulty valve.
Coffee dose is too low
Using less than 6.5 grams will result in too low an extraction pressure and not enough coffee oil being available to make a single espresso. Increase the dose of coffee to at least 7 grams per single shot of espresso.
The rule of thumb with espresso grind size is that the coarser the grind is, the faster it will pull the espresso. What is this? So, if you're looking to slow down the pull of your espresso, then you'll want to change to a finer grind.
As your shot pulls, you should see a change in color. Depending on the roast level and roast date, this will look different but typically, in the early stages of a shot, the espresso is very strong, syrupy, and dark in color. As it continues to pull, it changes to a vibrant orange to a pale blonde.
It involves changing the quantity of water you'd use in a typical espresso recipe. You double the water quantity for the same quantity of grounds. The extra water gives you a larger shot of coffee, richer caffeine, and unique, deeper notes of the concentrated flavor of the coffee.
If you drink one espresso shot (which has about 50-65 mg of caffeine) and your personal caffeine half-life is about five hours, you'll have a pretty negligible amount of caffeine in your system ten hours after ingestion.