Ice Cubes Are The Secret Ingredient For Vibrant Pesto

When it comes to a fresh yet savory burst of flavor, it's hard to beat a rich, herbaceous pesto. However, many home cooks are disappointed when their expectations for a vibrant green spread go unfulfilled. Instead, they end up with a pesto that — while still tasty — has a less pleasant, brownish hue. Luckily, the ingredient at the center of an easy way to prevent your pesto from browning is in the freezer.

Prepare your pesto ingredients as usual, and place them into your food processor. However, before blending everything, add an ice cube or two. The intense cold shocks the herbs, which stops the browning process.

If you're curious how the trick works, it comes down to the science of enzymes and oxidation. Finely chopping basil activates a compound called polyphenol oxidase, which causes oxidation and other reactions that turn green or colorless substances in the leaves black and brown. By lowering the temperature of the pesto mixture as it comes together, the ice cubes help slow these reactions, though they won't stop them completely. 

It's important to note that even though pesto with a bit of browning may not look as pretty, this reaction won't impact its taste. Likewise, as this hack essentially adds cold water to the mix, ice cubes don't change its flavor or affect the length of time your pesto will be good to eat.

Beyond the ice cube trick, other ingredients and techniques can play key roles in preventing unattractive browning and preserving pesto's healthy green color. One option is to briefly blanch basil in boiling water, which damages or destroys the enzymes responsible for browning. However, some argue this can slightly dull the flavor of the basil. Therefore, other cooks prefer adding a splash of lemon juice to their recipe. In addition to providing a tangy kick, the acidic juice lowers the pH of the mixture, another method of halting the chemical browning process. 

However, with no additional time spent, steps added, or ingredients that alter the condiment's flavor, it's easy to see why the ice cube hack is the preferred choice for many home cooks.