Solving The Problem of Pesto Genovese
As soon as fresh Pesto Genovese hits hot pasta, it turns muddy brown
A brighter, greener pesto gets an assist from antioxidant-rich arugula.
Pesto is often misunderstood. You can change up the herb, the nuts, the cheese, and/or add other ingredients; there are thousands of variations. But Pesto Genovese, the most common pesto, has a color problem. When you blitz the leaves with garlic, nuts, cheese and olive oil to make pesto the color dulls and darkens and when it hits hot pasta, the problem gets worse. Store the pesto for a day and it goes full-on mucky. Sure, it tastes fine, but there’s no arguing about its appearance which wouldn’t matter if we don’t also eat with our eyes.
Basil contains enzymes and compounds that, when the herb is cut or processed, trigger oxidation and produce brown pigments. Blanching deactivates the enzymes, preventing discoloration. This technique does indeed work, but we quickly learned blanching also obliterates basil’s sweet-spicy, anise-like notes. Without those flavors, there’s no point to pesto.
We then tried chilling the food processor blade and bowl, as cool temperatures slow oxidation. (Heat hastens the oxidation of basil. This is why vivid-green, freshly made pesto tossed with hot, just-drained pasta quickly turns drab.) But this was not effective.
Next on the list was acid, which slows the enzymatic activity that causes oxidation. We were surprised by how well a tablespoon of lemon juice stirred into the finished pesto staved off browning. The citric acid did alter the flavor of the pesto, but once the pesto was tossed with pasta, it was barely noticeable. Pleasant, even.
We had one more thing to try. Instead of trying to prevent or delay oxidation, we wondered if we could obscure it. Turns out, introducing another green to the mix—one with fewer enzymes that cause discoloration and more natural antioxidants like vitamin C—worked beautifully. We made pestos with a few different leaves of the dark-green persuasion. Arugula won, its pepperiness paired nicely with the sweetness of the basil. A 2:1 basil to arugula ratio hit the sweet spot. This pesto kept its vibrancy even the day after it was made.
Of course this evergreen pesto can be used on pasta. Or it can be swirled into soups such as minestrone or tomato bisque. We, however, opted to toss it with potatoes and green beans, a noodle-free twist on the classic Ligurian dish trenette avvantaggiate. It’s a mayonnaise-free potato salad perfect for high summer and early fall.
Like the millions of other pestos out there, evergreen pesto should be stored with a layer of olive oil covering its surface to prevent exposure to air. It will stay nice and green in the refrigerator for up to three days.
Dawn Yanagihara
A native of Southern California who, as a kid, spent many summer weeks in her parents’ home state of Hawaii, Dawn Yanagihara studied studio art and French language and literature in—where else?—upstate New York. After graduating and spending half a year trying to figure things out, she realized she was much better at making food than art and preferred to eat madeleines than read about them. So she attended culinary school on the East Coast and took courses in pâtisserie and viennoiserie at École Lenôtre in France. In Boston, she worked late nights and early mornings as an assistant pastry chef in an esteemed French bistro where she learned restaurant baking wasn’t exactly her cup of tea. She then accepted a job as test cook at Cook’s Illustrated magazine and has been in food publishing ever since—as a recipe developer, copywriter, website editor, author, cookbook editor, and food editor. Now living back in Los Angeles, she is still very keen on baking, loves sweets, and is smitten with the food and culture of Thailand. She chooses cocktails over wine, waffles over pancakes, and onion rings over French fries.
