I have seen some commercial machines promoting "pulse brewing" as though it is advantageous to the coffee. It seems to me to simply be a cheap alternative to proper flow control.\r\n\r\nSome machines have their water gravity fed to a sprayhead (rather than pumped or flow controlled), these machines always have the same head of pressure so when fully open they allow out say 3 litres in 60 seconds. They usually operate on 30 second cycles. So if you want 4 litres over 4 minutes, it will open 10 seconds and close for 20 seconds, allowing out 500ml in that 30sec cycle, so allowing 1 litre per minute, and 4 litres over the 4 minutes.\r\n\r\nNow is there any advantage to the coffee by having this pulsing, or would a lowered continuous flow rate (1 litre per minute) result in a better coffee?[/b]

I've never heard about "pulse brewing"...

Pulse brewing allows for adjustments to the water contact time with the coffee. Depending on the coarseness of the grind, and other variables, people will want longer or shorter water contact time with the coffee, to get more or less extraction.\r\n\r\nIt seems to me the companies decide on the highest flow rate anybody would want, say 4 litres per minute. So if set to this the valve to the sprayhead simply stays open constantly. If they want 2 litres per minute it will be open for 1/2 the time.\r\n\r\nI would think the shorter the intervals the better, i.e. 1 second on , 1 second off, but this probably would disrupt the even flow of the water. The one I have seen, a Fetco, uses 30second intervals. I feel a constant lower flow rate would work better. If you use long intervals the coffee at the top of the basket is drenched and then quickly drained, while the coffee at the bottom is always submerged. This would give uneven extraction of the coffee. With a constant flow the extraction would be more even.

Actually I am not a coffee expert so it's hard for me to talk about such things, but I understand now what you're talking about.