The hot components of spicy foods generally are synthesised by biochemical processes within cells. In many cases the cells do not actually synthesise the final product, but harmless precursors that only produce the usually significantly toxic product when those precursors are brought together if the cell happens to be damaged. A spectacular example of this is in the formation of mustard oils; a mustard seed typically has a mild flavour, but if you crunch it between your teeth and keep it in your mouth for more than a few seconds, you will notice a spectacular, progressive change.

However, many other substances are indeed matured within the cell walls, and remain there. Plant cell walls commonly contain highly resistant substances such as cellulose, suberin, and lignin, so some of them survive the process of preparation and cooking so that the spice uselessly passes through our digestive processes to plague or please what ever coprophages might happen to encounter it subsequently. However, freezing causes the largely aqueous contents of plant cells in food to swell, and frequently to burst the cell walls. This releases cell contents, increases the digestible fraction of the food without reducing its value as a roughage, and increases the perceived spiciness of the dish. Perceptive cooks often make use of such effects when appropriate.

My mother always used to make a curry the day before it was to be eaten. She maintained that this was the "right" way because they tasted better when reheated.

It's a brave man who contradicts Jon, so I want to make it clear that I agree with all he says. However, the traditional "hot" spice for curry was black pepper, which is crushed before it is cooked, so the cell wall doesn't need rupturing. The heat in modern curry often comes from chili, the capsaicin which makes them hot is accessible without cell rupture because it is the plant's protection against mammalian browsing. Other spices are usually ground with a pestle and mortar - cumin, coriander, turmeric, fenugreek etc. - so complete cells are broken before cooking.

A traditional curry chef always fries the spice in very hot oil, before adding other ingredients, to "release the aromas" [typically, the procedure is to fry onions and then raise the heat and add the spice]. If that doesn't see off any remaining intact cells, I don't know what would.

If I had a trench, I'd retreat to it now.

ello Pete,

cell rupture is tho only reason specific to freezing I know.

Of course nobody ever has made a duble blind experiment

on this.

Tast (which is 90 % smell) is a sense which depends a lot

on actual situation of the person (helth etc) and it is

easily betrayed by preoccupation.

For this :

comes from chili, the capsaicin which makes them hot is accessible without cell rupture because it is the plant's protection against mammalian browsing

there is a different reason, Yo give it in the last two sentences of Your post:

Capsicain, as many (or most) aroma stuff is lipophilic.

This means, it is soluble in fat only.

Georg

PS Every country (or county) has some dish(es) , which are said to be much better

on reheating. This is a German "Poem" on that:

(The English version misses this detail)

Eben geht mit einem Teller Witwe Bolte in den Keller,

Daß sie von dem Sauerkohle Eine Portion sich hole,

Wofür sie besonders schwärmt,Wenn er wieder aufgewärmt. -

>cell rupture is tho only reason specific to freezing I know<

Just so, Georg.

And having conceded that, I must concede the point to Jon as well.

I wonder if the phenomenon is restricted to dishes that have been heated, frozen and then reheated; or does it work without the freezing stage?

A slight digression: I am very happy to eat reheated stews of all sorts (in this I include curries, and all other meals where meat is cooked in a sauce), but I find the taste of chicken changes much more than other meat when heated up. Is there something unusual about me or the chicken?

Hello Pete,

re. chicken reheated, I agree with You.

On the other hand, fried chicken Ilike to  eat when cold,

what I do not like with other kinds of meat.

Being used to my mothers balkanous/vienna/south_gerrman

type of cooking, this is just because I'm used to this.

Georg