Here’s the explanation I promised in the last post—the explanation (with some additions and edits) I sent to Maurizio in reply to his questions about the experiments with thyme, oregano and basil:
Both oregano and thyme have pretty much the same chemical composition but in very different proportions. When I taste oregano by itself, it tastes like wood shavings to me, and when I taste thyme alone it gives the cold, turpentine flavor Maurizio described. Thyme has a chemical that is not in oregano to any great extent, namely alpha-terpineol, which has that flavor. However when you start with thyme then add oregano, you get the major chemicals in the right proportions and the right order in the mouth, and the result is quite delicious.
[The major chemicals in question are thymol, which mainly hits the cold receptors, and carvacrol which mainly activates the warm receptors. Thyme has more thymol, and oregano has more carvacrol. If you remember from my post on Basic Pairing Principle #3, the order in which you eat a food matters: cold first and warm later seems to work best.]
Add tomato, especially cooked in a tomato sauce, and the effect is truly marvelous, I think. The cooking gets rid of some of the potential off flavors such as alpha-terpineol, and the tomato helps bring the combination into the “warm” receptor realm. As noted above, the proportions of the chemicals in oregano, the proportion of carvacrol to thymol in particular, favor the warm receptors.
As for basil and thyme: fresh basil has a compound, anethole, which tastes sweet and is very persistent. Activating the sweet receptor as intensely as this inhibits the bitter receptor, so bitterness disappears. Now the warmer notes of the carvacrol in the thyme have a chance to appear, though the initial attack will be cool due to the higher quantity of thymol in thyme. Thymol activates both the cold and the warm receptors, but you need a higher concentration of it to activate the warm receptors, unless the warm receptors are activated by carvacrol or by compounds in basil first.
By contrast with tomato sauce, insalata caprese would be terrible with thyme and oregano because you would get them separately and/or in the wrong order in a mouthful. By contrast, you can add fresh thyme to the basil with insalata caprese because the effect of the basil is long lasting, so it carries over from mouthful to mouthful. In addition, the fresh tomato brings out the basil, as does the balsamico, and the balsamico, in turn allows the sweet to become prominent by inhibiting bitter through its acid. I know that you classically don't add thyme to insult cappers, but I've given it a try infused in the balsamic, and it's delicious.