Here’s Why Your Pesto Sauce Is Not Bright Green

Discover the main reason why your pesto has that unpleasant brownish color and how the bright green color can be maintained.

You have some fresh pesto that you stored in the refrigerator. When you pulled it out, the surface is brown. In this article, we want to dwell on another thorny issue: how to keep pesto from turning brown; in fact, the green basil sauce also has delicacy among its characteristics, and it is not uncommon to notice how, despite its freshness, it has become dark.

So, let’s find out together why this happens and the secrets to avoiding it.

Table of Contents

    Why does pesto turn brown?

    Pesto does brown a bit when exposed to air, even when stored in a tightly sealed container. The main culprits for this browning pesto are polyphenols, the same molecules that make many other foods dark, such as fruit and vegetables, and basil, the main ingredient of pesto, is very rich in these polyphenols

    The polyphenols, when exposed to oxygen undergo a deterioration process called oxidation, to which olive oil, another ingredient in pesto, is subject. Furthermore, the oxidation process is facilitated by polyphenol oxidase, which looks like a tongue twister but is actually an enzyme that blackens the polyphenols contained in the basil leaves.

    A further factor that increases oxidation is high temperatures. Therefore, we can deduce that the main enemies in the preparation phase of pesto are heat and oxygen. So let’s see how to proceed to avoid putting in place the oxidative process, responsible for the darkening of the basil leaves and pesto.

    However, you should not be afraid of oxidized pesto. You can always scrape off the top if it looks too unappetizing, or you can mix it well before serving.

    How to prevent your pesto from turning brown

    Now that we have established why pesto turns brown, here are some tips that us can use to prevent it from happening:

    Blanch the basil

    The best way to prevent it is to blanch the basil leaves in boiling water for a few seconds, and then cool them immediately in a bowl of water and ice. In fact, if the heat is able to activate the enzymes, a high temperature can completely deactivate them, preserving the color of the pesto for a long time. Furthermore, when making it, it is necessary to choose only young, fresh basil leaves.

    Pour a little olive oil over it

    Another way is to drizzle a small amount of olive oil over the top, just enough to completely cover the pesto. This, in addition to counteracting darkening, helps to increase shelf life.

    Before serving just pour off the oil and mix any remaining into the pesto. The basil leaves can also be immersed in extra virgin olive oil. The pesto must also be kept in a closed container and away from heat sources.

    Cover with plastic wrap

    Another trick is to keep the air from getting to the pesto. You can do this by placing a small piece of plastic wrap directly onto the top of the pesto creating a seal, and blocking out the air.

    Freeze the tools

    The equipments/tools that you use determines how your pesto will turn out. Try to avoid using the food processor or blender repeatedly as this could overheat too much , increasing the chances that it will turn black.

    Use a mortar and pestle instead. When using these, make sure them in the fridge half an hour before its realization: small tricks, but which guarantee its classic bright green colour. Howevr, if you don’t have them, you can also do this for the food processor bow and blades.

    Add lemon juice

    Another trick to prevent it from happening in the future, you can also introduce an acid like lemon juice into the recipe. Just don’t use too much as it will change the flavor.

    I hope you find these tips helpful.

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