How do you neutralise oxalic acid when cooking?

Question

Particularly with chard and spinach in soup.

Answer 1

Is it really oxalic acid? I would not be surprised, but I always thought it was poisonous. This is why one is not supposed to eat rhubarb leaves, because they contain it.

Neutralising an acid is very difficult in cooking. The only alkaline foodstuff that I have heard of is egg white, but that would coagulate in the soup and have to be drained off. You could try it, though.

Answer 2

I don't think the amount of Oxalic acid would be significant - it is present in these vegetables in tiny amounts for sure, but too little to taste and certainly not enough to be toxic.  

If you want to neutralise an acid you have to add some alkali - the most commonly available one which is safe is baking soda (sodium bicarbonate).  In the case of spinach you are more likely to get a flavour from the baking soda than from the tiny amount of acid you might neutralise.

If you want to try it just add a tiny amount of baking soda (like the small tip of a teaspoon) to the spinach while it's cooking.  However, even if you do this you will still have sodium oxalate present, and that probably tastes the same as oxalic acid because it is the oxalate ion which will affect the flavour rather than the acid per se. Oxalic acid is too large a molecule to evaporate off like acetic acid does when you put vinegar on chips.