Reducing acidity without creating "soapy" taste It is well known that sugar is used to reduce the acidity in tomato sauce.
Yet there is no chemical reaction going, just a shift in taste. The PH remains the same. (Does adding sugar to tomato type sauces affect acidity?)

To be clear: I'm not looking for ideas on how to make the food appear less acidic. My intention is to change the pH-Value.

In nature it's quite easy to find acids, but I'm struggling to find a base suitable for cooking which won't give the food the distinctive soapy taste (for instance for a lemon-compote or... tomato sauce).

There are actually not many bases which would dissolve in water and might be safe for cooking. I conducted some research and came up with Lime (calcium oxide), Alcaloides (wich are mostly not safe), ashes or Calcium hydroxide (like to be used in Nixtomalisation - which I have successfully tried, but in the end the Ca(OH)2 is to be washed out after the process), Sodium Bicarbonate (baking soda, but sure this is a base?)

Here's a list of bases and their pH-Values which are supposed to be used in cooking. I'm lacking of experience in their usage and would be grateful if someone could share how it was deployed:
https://bakerpedia.com/ingredients/bases/
I use Calcium hydroxide, (pickling lime, Cal, slaked lime), to raise the pH of my tomato sauces. It does not take much, and you don't get that nasty flavor that comes with using sodium bicarbonate. You can find the stuff in the canning aisle in a U.S. grocery store. Mexican and Asian stores  also usually carry it. The Latinos use Cal to nixtamalize corn prior to making tortillas. An eighth teaspoon, or 0.2g, is usually enough for 250ml  (a medium can) of tomato sauce. You'll have to play with that number a little. I've tried several different bases to neutralize the acid they add to tomato sauce. Only Calcium hydroxide seems to have no down side.
If you are adding the right amount of finely powdered CaOH, you shouldn't have to wash it out, as it will turn into Ca citrate, or some other soluble salt. You may well be using too much. The reaction does take time, so 10 min or more waiting is not unreasonable.