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OK, what happened to my pesto?

A couple of days ago, I found some picture-perfect Genoese basil at my local farmstand. I took it home, threw it into the food processor with the other requisite pesto ingredients (pine nuts, good olive oil, Parmesan, salt, pepper, garlic) and made a lovely looking and aromatic pesto. I decanted the stuff into a glass bowl, coated the top with more olive oil and put it in the refrigerator, well wrapped, where it stayed, sealed, for 24 hours.

When I sauced some pasta with this pesto the next day, it oxidized on contact, turning a dull olive brown color. Worse, it lost a great deal of its flavor.

Can any of you help diagnose the problem? Was my mistake storing the stuff? Does homemade pesto need to be used immediately? And if so, how does all-natural, commercially packaged pesto retain its color and flavor sitting in refrigeration for considerably longer than a day?

Any and all advice would be welcome!

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  1. It needs to be used immediately, or frozen, in my experience. I freeze it in ziplock bags, flattened out really thin, so I can just break off a chunk. It keeps its color way better this way. Some people leave out the nuts when they freeze it, but I don't know why. You didn't do anything weird, basil leaves oxidize super fast.

    1 Reply
    1. re: Betty

      Leave out the nuts when you make it to freze; freeze it right away.

    2. I think commercial pesto has some kind of preservative in it, perhaps citric acid?

      I make pesto in bulk whenever I see good basil in the local markets. I find it turns brownish on the surface, but beneath that thin layer it's still a bright green. The flavor fades with time, but it holds up for a couple of months in the freezer. I should add that I look for Thai basil for my frozen basil, it has more intense flavor and this may make a difference.

      1. Thank you both--this is enormously helpful. I will trying freezing in Ziplocs, and using Thai basil.

        2 Replies
        1. re: lisacs

          Hi, you mite also try adding just a little bit of lemon juice to the pesto your going to hold for a day or so or freeze. I think it will help with the color and won't change the flavor if you use very little. Good luck--there is nothing like great pesto!

          1. re: jackie de

            I also use some lemon juice to reduce oxidization.

        2. Basil oxidizes easily when cut with a knife blade and exposed to air. For uses where it doesn't have to be pulverized it's better to tear it. Yet, I have some Costco Kirkland all natural pesto in my fridge for months that still looks and tastes fine. Label says it contains rice vinegar as the only thing I think would retard oxidation. If I wanted to make some at home I would do it immediately before eating, or maybe an hour before. You might be able to store it if you vacuum packed it in a plastic bag with one of those handi dandi electri vacuum sealers (Deni is a popular brand available reliably at QVC.COM)

          1. If I know I need to keep my pesto longer than it can safely sit out on the counter, I (VERY briefly) blanch the basil in boiling water -- 5 seconds tops -- then shock in ice water to stop the cooking. Pat dry, and it sets the colour.