San Marzano is the name of a variety of roma tomato, one that's a bit meatier, with fewer seeds than the usual roma tomatoes. But most importantly, San Marzano also refers to that specific variety of tomato grown in a specific region of Italy: the Agro Sarnese Nocerino of the Sarno River valley near Mount Vesuvius, where volcanic soils are said to produce sweeter, less acidic tomatoes. These are "true" San Marzanos, and their unique combination of varietal and terroir is so special that they're given official status as a "protected designation of origin" or D.O.P. (Denominazione d'Origine Protteta).
Trouble is, any producer can slap the words "San Marzano" on their label and charge a premium. Technically they wouldn't be lying if that's the variety they used. And heck, San Marzanos grown in California are pretty tasty too (just look at our taste-test here). In fact, if the taste tests at various other food publications are any indication, Americans seems to prefer the brighter, more acidic, and almost always far more generously salted flavor of American-grown canned tomatoes. Certified San Marzanos rarely take the top spot.
Maybe it's my Italian genes, but I think the sweet, rich flavor of true San Marzanos make them totally worth the higher price — especially for pasta sauces and other tomato-heavy dishes. I think it's amazing that they have a fraction of the added sodium of American tomatoes and yet don't taste bland at all. Also, they don't have any calcium chloride. American processors often add this ingredient to help tomatoes (especially diced) keep their shape. (I've checked more than 10 brands of American canned whole tomatoes and they all had calcium chloride added, which just makes it harder for the tomatoes to melt into a sauce.)
If you're going to pay the steeper price for imported tomatoes, then you want the certified real-deal — sweet tomatoes grown and hand-harvested in that vaunted volcanic Italian soil. To be sure you're buying the real stuff, look out for these clues.
- They must be whole or cut in half and packed in cans to be certified as authentic. Any other preparation (diced, puréed, packed in boxes) is your first red flag.
- Look for the words Pomodoro San Marzano dell'Agro Sarnese Nocerino, which indicates the tomatoes were grown in the special region.
- Most important: Look for the star-shaped D.O.P. certification symbol, which will have the words, Denominazione d'Origine Protteta. Next to it will be an I.D. number. This is guarantees they're certified by the D.O.P. consortium as true San Marzanos.