Canned Whole Tomatoes

If you believe all the hype from Italian chefs and cookbooks, then San Marzano tomatoes are the best tomatoes in the world. Promoters of the prized crop claim that the climate and fertile soil in the eponymous southern region of Italy where they grow are behind the fruit’s meaty texture, juiciness, and exceptional flavor. Only tomatoes grown in the region from seeds dating back to the original cultivar and according to strict standards may receive the elite Denominazione d’Origine Protetta (DOP) label. In the past, San Marzanos were hard to come by in the United States, but that never deterred loyalists, who sought out cans from gourmet markets and online retailers. In recent years, however, San Marzano tomatoes have become easier to find, showing up in regular supermarkets and under different brand names. That’s partly because not all brands labeled “San Marzano” are DOP-certified. These days, some of the tomatoes are even grown in the United States from San Marzano seeds.

Regardless of where they’re from, the wider availability of San Marzanos renewed our general interest in canned whole tomatoes—a product that we frequently prefer to diced or crushed. (Oftentimes, the latter two are selected from fruit that’s been damaged during harvesting and have been more thoroughly treated with firming agents to prevent them from breaking down.) We decided to hold a taste-off: San Marzanos versus everything else. After collecting 10 different brands—three labeled San Marzano, the other seven a mix of Italian, Canadian, and American products—we sampled them straight out of the can as well as simmered in both quick- and long-cooked tomato sauces.

Our questions: Are San Marzanos really the ultimate canned whole tomatoes—that is, bright, sweet, and tangy, with meat that’s plush and soft enough to melt into a sauce but without completely dissolving? More important, would they taste noticeably better than regular tomatoes once they’d been cooked down in a sauce with aromatics and wine?

Surprisingly, the answer to both questions was a definitive “no.” Though each of the three San Marzano samples elicited a few lukewarm compliments here and there—“agreeable flavor”; “nice blank-slate tomatoes”—none of them delivered the bold, deeply fruity taste that we were expecting, nor did they hold their shape well. In fact, these tomatoes scored well below several of the domestic samples, the best of which were deemed “bright,” “complex,” “meaty,” and—as one taster noted in amazement—like “real” tomatoes.

Also remarkable: Whether or not the tomato was a true San Marzano didn’t matter. The DOP-certified brand was actually our least favorite of the three, which debunked the hype over the San Marzano pedigree once and for all. But now we had a more challenging question to answer: What made the other samples taste good?

Sweet and Sour

For starters, sweetness. Scientists gauge this particular quality in tomatoes according to the Brix scale—a measurement of the sugar (per 100 grams) in liquid. Generally, the higher the Brix of tomatoes, the greater the perception of good, ripe tomato flavor.

When we had an independent lab measure the Brix of each brand’s tomato solids, the results were conclusive: Our three least favorite brands (including the DOP-certified San Marzanos) were the least sweet, with tasters panning their “weak,” “washed out” flavor, whether cooked or eaten straight from the can. Conversely, tasters praised the “fruity,” “real summer” sweetness of our two favorite tomatoes, whose sweetness levels were relatively high. However, the sweetest samples of all—which happened to be the other two San Marzanos—landed in the middle of the pack, proving that when it comes to optimal tomato flavor, sweetness is not the only dynamic in play.

The other half of good tomato flavor is acidity—and lots of it. Bright tanginess balances out the sweetness and (like salt) enhances other pleasing flavors by masking bitterness. Sure enough, when we had the lab measure the pH of all the samples, we discovered that the tomatoes with the lowest pH (i.e., the most acidic tomatoes) almost invariably scored the highest, earning tasters’ approval for their “fresh,” “fruity” flavors, while the least acidic tomatoes tanked. The lone exception was our bottom-ranked brand, which boasted a good level of acidity but not much sweetness—a combination that gave it an “unbalanced” flavor that tasters assailed for being “nothing like a summer tomato.”

Salt played only a relatively minor role in our overall preferences. The American samples contained a lot more sodium than did imported brands (at least 20 times more, in some cases), and in the plain tasting some tasters preferred them for it. But sodium levels didn’t influence our preferences in either of the cooked applications, and since canned tomatoes are rarely eaten uncooked, we didn’t factor salt content into our rankings.

In the Flesh

Good balance was the key to optimal tomato flavor, and it was a quality that tasters looked for in the fruits’ texture, too. Overly firm specimens lost points for their “rubbery” bite, while tomatoes that broke down completely were docked for “mushiness.” Our three top-ranking brands boasted a firm but tender bite, even after a lengthy simmer. But what accounted for the differences in texture?

For one thing, calcium chloride. All five American products were treated with this salt, which manufacturers add to maintain the tomatoes’ firmness, whereas the imported brands were not. We figured that for better or for worse, the widespread use of this additive in domestic canned tomatoes couldn’t help but drive our American tasters’ preference for tomatoes that retain a little structure.            

While we liked the tomatoes to be somewhat firm, we didn’t like their flesh to be overly thick. In the 1960s, mechanical harvesting replaced handpicking in this country, speeding up the process. Growers then had to breed a tomato sturdy enough to withstand the rigors of machine harvesting, which meant they needed a fruit with thicker walls (known as pericarp). The trade-off was less flavor. The reason? Tomato flesh isn’t where most of the flavor is; it’s in the “jelly” that surrounds the seeds in the fruit’s hollow spaces. When the flesh got thicker, those cavities got smaller, leaving less room for the jelly.

To see if this trend lined up with our results, we took a sample from each can, measured the thickness of its pericarp with a caliper, and scooped out and weighed its jelly. Indeed, our least favorite tomatoes had the thickest pericarp, with tasters describing them as “tough,” “chewy,” and “bland.” The tomatoes we liked best had thinner, tender-firm walls, and their cavities were the largest and most full of flavorful jelly.

American Beauties

As it turned out, the San Marzano hype was all for naught. We didn’t even prefer Italian-grown tomatoes. Rather, we most enjoyed the bold acidity, high sugar content, and firm bite of our favorite all-American brand. Another American brand finished a close second, with tasters particularly admiring their firm texture and pleasing acidity. We’ll be stocking up on both.