Two things that I did not know previously about spices, but learned while eating white peppercorns purchased at the Spice Bazaar in Istanbul, during a break from reading this evening:
The difference between black and white peppercorns is somewhat similar to the differing means by which white and red wine are produced. Black peppercorns are the dried fruit of Piper nigrum, a flowering vine. The colour is the product of browning enzymes released from the fruit’s flesh through the application of heat, after picking and before drying. The important odour-contributing chemicals present in black pepper are part of a class of molecules called terpenes. White peppercorns, by contrast, are the product of fruit that has been soaked, decomposed, or otherwise removed – leaving only the seed to be dried.
This strikes me as somewhat similar to how red wine is produced from juice that includes skins, seeds, and stems – whereas white wine has such elements filtered out. The chemical result of their inclusion (called maceration) produces the tannins that give flavour to red wine. Those who are restricted to the appreciation of the cheaper examples of both varieties might find it useful to know that red wines contain more congeners than whites, and thus are more likely to leave you feeling rotten the next day (though the relevance of these molecules to the situation seems to be disputed; some argue that hypoglycemia, dehydration, and vitamin B12 deficiency are more to blame). Red wines also include tyramine, an additional metabolic toxin absent in whites.
One molecule mentioned frequently on this blog is capsaicin: the hydrophobic, colorless, odorless that makes chili peppers spicy. It does this by virtue of stimulating vanilloid receptors of subtype 1, normally sensitive to heat and abrasion. I thought that normal table pepper relied upon the same substance, but it actually depends on a molecule called Piperine, potentially notable for the fact that it interferes with biochemical pathways relevant to drug metabolism.