One of my molecular cookbooks goes into the use of acidity / alkalinity in cooking. What it doesn't describe is what safe pH values are that you can still serve food at.
Note: I am not looking for danger or 'cooking at the edge'. I'm a chemical engineer by training and won't be likely to mess this up, and yes, I'd have access to litmus paper or similar tools.
If the 'safe' range is broader than a (commonly) accepted range where food still tastes good, that'd obviously be good to know as well.
According to this neat chart on Wikipedia: http://en.wikipedia.org/wiki/File:PH_Scale.svg
Lemon juice is around 2, and baking soda around 9. Our digestive juices are around a 1, so it's probably safe to go a bit less than 2, but you wouldn't enjoy it. Baking soda is 9, and milk of magnesia is 10...both of which are safe to consume in small quantities, but I wouldn't want to serve a dish in that range.
So...I'd probably stick with 2-9 as an acceptable safe range. As far as taste goes, we're not really wired to enjoy the taste of alkaline. Between 2 and 7 (acid to neutral) is the tasty range.
some recipes, like Ramen noodles, require a water solution with a pH of 9-10. Kansui, the water that they use to make it, comes from a lake in Mongolia that is very alkaline, but if you know edible bases (b. soda is not quite strong enough to change the pH of water and still be tasty) you can probably find something that will work for you.
At pH 9 flour will change so that the glutens, flavinoids and aminos start to react, which is why ramen is yellow.
There aren't many foods out there that we eat that are basic. Sugars, proteins, and fats all break down into things that are acidic. Rainwater is mostly acidic, but there are lots of places, like the interior of the US where the pH of groundwater is about 8.3 or slightly more and it's perfectly drinkable. Our DnA is an acid (obvious from the A part of it). Since DnA is acidic, all of life is acidic. That means that the things that are basic are usually not plant or animal derived. WE are hard wired to eat things with a pH of 5-8. If you are a chemical engineer you should know the pH range of the average living organism. below 5 and it tastes tart. Above 8 and things taste soapy or chalky, for the most part. after 10, and you are getting into dangerous territory but you can go all the way down to 1 on the acid side, it's just a matter of how much you want people to pucker up when they eat your food. for the most part, edible acids will just mix up in the already acidic stomach with little fanfare.
