I chose San Marzano tomatoes for the sauce not because I knew what they were, but because the label said they were Italian tomatoes “From Italy.” Yes, they were more expensive (about double the price of other canned tomatoes), but the recipe called for them, therefore there was no other way. And, I’m sad to report, I’ve continued buying San Marzano tomatoes, without knowing what they actually are or if they’re actually worth it, for any recipe that calls for them.
I've had it with my willy nilly tomato buying!
me, to myself
Recently, I said enough. I've had it with my willy nilly tomato buying! Here’s what you need to know about San Marzano tomatoes:
Where they come from:
Italy (duh) but, more specifically, Mount Vesuvius. The volcanic soil makes them sweeter, less acidic. Authentic San Marzano tomatoes will be stamped with an official DOP (Denominazione d’Origine Protteta)—the same kind of certification and set of rules used for identifying wines grown in certain locales in Italy. (So, these are real and these are not.) DOP basically means "protected designation of origin" and ensures the quality of the tomatoes. Here are all the DOP regulations for San Marzano tomatoes, translated from Italian.
What makes them different:
Besides their sweetness and lower acidity, San Marzano tomatoes have firm pulp, easily removed skin, and less seeds. Authentic San Marzano tomatoes are only sold canned peeled whole or cut in half, so if they’re puréed, chopped, or diced, then they’re not the real deal (see the following point).
Can they be grown outside of Italy?
Yes and no. There are domestically grown San Marzano tomatoes, however, remember that DOP certification? Its rules ensure strict growing and canning standards and quality, which means domestically grown San Marzanos will taste a lot different. As The Kitchn says, “It's comparable to the difference between French Champagne and sparkling wine from California.”
Are they worth it?
In a word, yes—especially in dishes where the quality of the canned tomato shines. (Like, for example, tomato sauce or on pizza, but not in chili.)