What gives “diner” coffee its distinctive taste?

Question

At least in the US (and probably elsewhere), late-night diners are a popular place to get a cheap cup of joe. In my experience, diner coffee has a taste that's generally not found elsewhere (most people call it "bad", but that's not what this question is about).

I'm wondering what causes this taste, and how they all get such similar tasting coffee? I assume the brewing process has something to do with it (those big commercial drip brewers which they all seem to use), but I've been to other places that used those with various different roasts and they all tasted different.

So what else makes diner coffee taste like diner coffee? Examples of the kinds of places that serve this include chains like Waffle House, but also individual / locally owned diners.

Answer 1

I think it is a combination of old stale grounds sitting on a burner for long hours. The places you mention are generally open 24/7 or something close to it and have people ordering coffee at all times of day, so it's all made ahead of time and kept warm all day.

The cheapest coffee suppliers usually mix beans from all over the place and they all store them way past any freshness date. Diners run on small budgets and generally buy the cheapest stuff, thus they all have the same "flavor".

That combination is not just a diner thing, I would also say it is the same as cheap gas station coffee in the US.

I would knock it more if it didn't keep me awake behind the wheel more than a few times.

Answer 2

Comments on the question above, but I'd expand this as an answer as well because I don't see it mentioned yet.

Another possibility of "diner coffee taste" could be due to the use of robusta rather than arabica. Robusta tends to be cheaper than arabica, so this might also be a reason for its use (and the cited "cheapness") of the cup. If you're used to fancy cafe coffee (which tends to be arabica), it's a rather different (albeit not necessarily unpleasant) experience. See also this question on arabica and robusta.

Granted, this arabica/robusta distinction is oversimplification, because there are so many varietals, but here's one article on differences. For example, robusta tends to have lower acidity, but higher bitterness. If these are the attributes you attribute, it might be further robusta evidence.

If you were to learn the brand of coffee being brewed, that might suggest the variety of the beans, but that's probably difficult to learn from generic, anonymous diners.

Answer 3

Diner coffeemakers like Bunn store water in a tank and keep it hot 24/7, and then run the hot water through the grounds very fast. Diners like this because they do not have to wait for the water to heat up and the coffee brews fast and stays relatively hot. But as we all know, this makes the water flat (not to mention calcium build up in the tank) and there is insufficient contact to extract all the flavor from the coffee. I have tried a Bunn "diner" coffeemaker at home and while the coffee comes fast and stays hot, flavor suffers.