Did the flavor run away when it got cold? Reheated pizza always seems to be much blander than fresh, hot pizza. Surely there is an explainable reason.
The flavors have gone away in a sense. Many of the ingredients have had their basic chemical structure changed after the initial baking period. Then when you stick it in the refrigerator, the ingredients change again. Then if you microwave, you change their structure again. Not a lot, but enough that the taste and texture are different.
My guess is you heat a lot of the extra grease out of it in the microwave. (P.S. I have no idea)
I always preferred the taste of reheated day-old tomato sauce (as for spaghetti & meatballs) to the “fresh” stuff.
It seemed to taste more “piquant…” which I attributed to a kind of chemical reaction/fermentation.
This BBC story rejects your premise, and notes that the reason pizza tastes so good the next day is that the tomato paste prevents the fat from seeping down into the crust, and making it soggy.
Most of your sense of taste is actually your sense of smell. Cold pizza means less pizza vapour means less taste.
This is the main reason most Americans (and Canadians for that matter) drink swill for beer straight out of the bottle. If it’s ice cold it’s tough to have any taste at all.
Anybody who knows antthing about baking breads and pizza will tell you that moisture is everything.
The cheeze and the sauce are ruined after they lose so much moisture…especially after a reheating.
Now, there are people who are fans of cold pizza (cold leftovers)…and they refuse to heat it up. Heating it up will dry it out. Bbut surprisingly - or maybe not - the cold pizza has more moistuire in the sauce and the cheese. The refrige does seem to help the pizza from drying out.
I never thought of chomping on cold pizza until I got fed up with reheated pizza. Cold pizza is definitely better in terms of the cheese and sauce flavor.
It’s all about moisture.