Acidity in coffee has been a conversation that I have a hard time wrapping my head around. I always equated it to crappy coffee, but it appears to be more than that. I am usually engaged in this conversation as it pertains to "low acid coffees" or cold brewing.
I have to be honest, "low acid coffee" is something that never made sense to me. I use to experience having an upset stomach after drinking coffee, but it was only ever after the crappy coffee my company provided for free. When I started bringing in my own good coffee, I didn't have the same problems. So I concluded in my very scientifical experiment that it is due to crappy coffee. With that conclusion in my mind, I always thought "low acid coffee" was just a gimmick, like Bullet Proof's "extra healthy" coffee.
The only other time I have ever discussed acidity is as it pertains to cold brew. Cold brew coffee has been the bandwagon for quite a while now. A lot of people love it, so there has to be something to it. I personally prefer hot brew over ice. The reason being...acidity. Hot brew over ice (to me) is much brighter and livelier. Cold brew is just kind of muted to me. So I concluded again that people were confusing the flavors of acidity with actual acid (because you don't get upset tummy's from good coffee, remember ;).
I was going to do a post on composting coffee grounds and everyone was making stink of how acidic coffee and coffee grounds are. Which is what got me looking into this. (I may still do the composting post at some point.)
I found this article http://www.coffeeresearch.org/science/sourmain.htm and it helped me understand quite a bit. I will admit that it is slightly over my head in a lot of ways, but I was able to make sense of most of it.
From what I could find, coffee has a pH level of about 5, which is not the most acidic thing we drink, but it isn't exactly neutral either. So that gives validity to people who want "low acid coffee." People have every level of sensitivity to everything in the world.
Other factors that affect acidity in the cup were explained. Everything from where the bean is grown (higher elevations have higher acidity), to how it is processed (wet processed has more perceived acidity than dry processed), to the roast, and finally to how it is brewed.
As a brewer, this is fantastic information. I will be able to better understand what my customers are looking for when they say they need a low acid coffee. That doesn't mean I have to lose them as a customer, it just means I need to know what to offer.