Maybe you ought to learn to cook?

Clearly, he has experience in both of those things then. Unless you have the same level of experience his opinion is the more valid one.

Has he ever been evaluated by a psychologist for stuff like autism or food disorders? This sentiment is super common in those spheres.

I completely agree with him and I'm older. I also rather starve than eat what I don't like. it's been like this since I was little and growing up in a restaurant environment with both parents and now my partner all chefs. I remember my grandmother punishing me with "you don't leave this table until you have eaten" changed to "this is the only thing you will get, or go hungry". I never left the table, also slept at the table because I thought this is hell of a easy punishment and eventually she started bribing me with sweets and snacks and crisps. Which didn't work because I never ate and still don't eat them. (I had my first burger when I was 17, didn't like it, my first fizzy drinks I tasted in my teens and what is it with bubbles, disgusting. I had my first chupa chups or whatever it was called when I was six, I handed it back disgusted) As adults its way more easier to decline foods you don't like. But son being 27 is a sign that it's his fml to have a mum like this. And as for a mother of an adult child it doesn't affect you.

It could be a food related allergy. He may truly be experiencing the pain. He should seek out medical help.

Perhaps that should be brought up with a medical professional. And words like 'sensory processing disorder' should be involved in the screening.