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Preventing leftover avocado from turning brown too quickly

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nikki Feb 14, 2005 12:10 PM

What do you do?

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  1. k
    kc girl RE: nikki Feb 14, 2005 12:23 PM

    If you're not eating the whole thing, cut one half off and leave the pit in the other side. Spritz the flesh with lemon juice and warp in plastic and you're good for two days.

    Some say if you put the pit back in (to pieces or a guac) it will keep fresh, but I haven't seen that work. Coating the surface with lemon juice (or olive oil) and sealing in plastic will prevent the oxidization to some extent.

    6 Replies
    1. re: kc girl
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      farmersdaughter RE: kc girl Feb 14, 2005 12:29 PM

      This is the method I use when I happen to have leftover avocade (not often!) and works well if you are going to eat the avocado the next day, but I think it starts to decline in flavor somewhat after a day.

      Make sure the plastic wrap is pressed tightly against the entire surface of the cut side of the avocado to prevent air from getting there.

      1. re: farmersdaughter
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        Rudylee RE: farmersdaughter Feb 14, 2005 12:33 PM

        I learned in a cooking class recently that you can rinse the avocado in cold water when you first peel it. The chlorine in the water will keep the avocado green for awhile. Haven't tried it yet...

        1. re: Rudylee
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          bacchante RE: Rudylee Feb 15, 2005 09:11 AM

          I'm sorry, but that is a disgusting thought...

          and why I refuse to drink or cook with tap water.

          1. re: Rudylee
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            Eldon Kreider RE: Rudylee Feb 15, 2005 02:52 PM

            As other posters in this thread and prior ones have noted, avocado browning is due to oxidation reactions. Two principal methods for preventing oxidation are exclusion and the use of preferential oxidants (sometimes referred to an antioxidants).

            For exclusion you want to avoid contact with air. Leaving the pit in a halved avocado (not taking the pit out and putting it back in) and immediately covering the cut surface tightly with plastic wrap is a good example of exclusion. Any mixing or mashing will put air in the avocado, so exclusion only goes so far in protecting guacamole from browning.

            Ascorbic acid (vitamin C) is widely used as a preferential oxidant in food over and above its nutritional value. Since both lemon and lime juices have pretty good ascorbic acid levels, they are often used to both prevent browning and add flavor. Treating cut surfaces with lemon or lime juice adds protection beyond what can be gotten from plastic wrap.

            It has been quite a few years since I completed my chemistry degree, but I suspect that I still know more chemistry than Rudylee's cooking teacher. The idea that chlorine in rinse water would retard browning goes against any chemical reactions that I know of. Unless the water supply around this cooking school is truly weird in chlorine content, there wouldn't be enough chlorine in a water rinse to have any meaningful chemical effect even if chlorine provided any antioxidant action in the first place. I suppose you could keep the avocado submerged in water. That would keep out some air. If the faucet has an aerator, there would be so much oxygen in the water that it would largely offset any air exclusion from the water cover. I hate to think what the soaked avocado would taste like, though.

            1. re: Eldon Kreider
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              JRL RE: Eldon Kreider Feb 15, 2005 05:08 PM

              Was watching Michael Chiarello's cooking show a while back. He made pesto and sprinkled it with vitamin c, from a capsule if I recall, to keep it from turnng brown. Said it was a chef's trick. I imagine that it could work on an avocado, too, though not sure how it would affect the taste.

              1. re: JRL
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                Eldon Kreider RE: JRL Feb 15, 2005 06:14 PM

                Fruit Fresh is vitamin C plus water-soluble carrier. Ascorbic acid pills are so concentrated that they might make controlling the application a bit tricky. I recall my mother crushing vitamin C pills to use when canning or freezing peaches before Fruit Fresh was around.

                Since lime juice and avocado have such flavor affinity, I wouldn't try Fruit Fresh or crushed vitamin C pills. On the other hand, I doubt that lime juice on pesto would taste all that great but one never knows until one tries.

      2. r
        rebs RE: nikki Feb 14, 2005 01:45 PM

        put the pit of the avocado in whatever you are saving.

        3 Replies
        1. re: rebs
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          sbp RE: rebs Feb 14, 2005 02:09 PM

          The pit thing is a myth. The browning comes from oxidation. Only way to prevent is to keep air away. Plastic wrap on surface works to some extent, depending on porosity of the wrap and how tight the seal. Vacuum bags work. I suppose the area under the pit would stay green, but there's nothing to prevent browning of the remaining exposed surface.

          1. re: sbp
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            rebs RE: sbp Feb 14, 2005 11:09 PM

            when i make guacamole and store it in the fridge, i leave the pit in. only the very top surface of the areas farthest away from the pit of the guacamole turn brown. i also work in a restaurant and the cooks put the pits in the piping bags they use for avocado puree and avocado mousse to keep it from turning brown. yes, oxidation is an issue, but this method seems to work in slowing down the oxidation process.

            1. re: rebs
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              FlyFish RE: rebs Feb 15, 2005 07:12 AM

              sbp is correct - the avocado pit myth is just that and has been beaten to death (apparently not quite, I guess) in previous discussions here and elsewhere and controlled experiment. Harold McGee, without doubt the world's foremost food myth debunker, demonstrated in his book that the pit only prevents browning of the guacamole immediately under it (by preventing contact with air) and that a common light bulb has exactly the same effect.

        2. a
          AimeeP RE: nikki Feb 14, 2005 02:24 PM

          Many of the earlier posters address saving it for use in a day or two. If I find myself with an abundance of avocado that I KNOW I won't eat before they go bad I quarter, slice and pit them and put them in baggies in the freezer. Let them thaw - microwaving will make mush and you can use them in Guacamole, dips or spreads. Not as good as fresh but if you can't resist the big bag at Costco it's one way to go.

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