I had to reduce the acid in my coffee decades ago when I started getting GERD (Gastroesophageal reflux disease). I am very happy to say *it worked*.
First off the darker the bean, the less caffeine and acid. The heat destroys both, and darker beans are roasted for a longer period of time. So I always buy the darkest french roast I can find.
Second, 180f is the perfect temperature to heat water before making coffee as it gets the flavors WITHOUT the acids. Tastes better too. I know from testing that 3 minutes and 45 seconds gets 20 oz of water up to 180f in my commercial 1100 watt microwave.
Third, I mix 1/8th tsp of *fresh* baking soda (a year old won't work) with a gallon of filtered water, and this is the water I use for coffee. The baking soda neutralizes any acid that does manage to make it into your cuppa java.
Now this means you cannot use a coffee maker to make your coffee, 'cus they all go up to boiling, which ruins the flavor of the bean and makes for a VERY acidic drink. So I use a stainless steel coffee funnel, pictured at the bottom available at many online locations. I bought one just to save money on paper filters, but the first cup made me realize those paper filters were sucking the flavor out of the coffee too. Washing this in the dishwasher once a week will keep it from clogging up. Otherwise after a couple of months it takes too long to make coffee.
btw, I also use the 1/8tsp of baking soda with a gallon of koolaid, which cuts back on the citric acid so much that only 3/4 of a cup of sugar makes it sweet instead of having to use the recommended 2 cups of sugar per gallon. And if I do get heartburn, I mix one half a tsp of baking soda with 12 oz of water, and drink that AFTER the baking soda is completely dissolved. Super fast cure for heartburn, been using that for 20 years as well.
Hope this helps!!!!! I'm going to go make a cup of coffee now
EDITED: Oops, that's 24 ounces of water for 3:25 seconds for 180f. Brain fog......