Pepperoni is a type of salami known for its spicy taste. How Food Works reports that pepperoni is made of beef and pork ground up and combined with spices and flavoring. Then salt and sodium nitrate is combined with the resulting mix to cure the meat to prevent the growth of microrganisms. Then the meat is innoculated with lactic acid bacteria, as with yogurt and cheese. and is stuffed into casings. The pepperoni then undergoes two days fermenting and then another 12 days drying out. The resulting product is then sliced, packaged, and shipped to supermarkets and eateries.
One thing pepperoni is not is Italian. It appears to have been invented by Italian American immigrants starting around 1919. Some have even suggested that it more resembles a German-style sausage than anything found in Italy.
Pepperoni has since conquered the American palette, mainly as a topping for pizza, though some have been known to use the spicy salami in salads and other dishes.
Some more high end chefs have eschewed pepperoni, prefering more traditional Italian sausages and salamis. But even in the botique pizza world, pepperoni is starting to gain some acceptance. Artisan pepperoni is just starting to become available, made with organic ingredients and without antibiotics. One pepperoni maker is substituting celery juice for the nitrates as part of the curing process.