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I've been juicing up carrots with a centrifugal juice extractor. There's a lot of overhead (prep and cleanup) so it makes sense to do a big batch and keep it in the fridge for a couple of days.

Unfortunately, the refrigerated juice seems to turn brown pretty quickly. Here it is after 48 hours:

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The pulp has precipitated to the bottom and retains its pleasant orange hue, but the juice has turned an ugly and unappetizing brown. It tastes better than it looks, but the flavor has suffered too. It's pretty extreme at 48 hours, but there is significant browning even at 24.

I'm using refrigerated carrots and putting the juice immediately in a plastic screw-top (Ziploc) container in the fridge.

Is there anything I can do to keep my carrot juice looking and tasting fresh?

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    You could try crushing a vitamin C tablet and mixing that in the juice. I don't know if it will help, but I do know that it helps keep avocados from browning. – Jolenealaska Mar 16 '17 at 8:24
  • @Jolenealaska Carrot juice is already pretty high in vitamin C (8.5 mg per 100 g, about 1/3 as much as lime juice) so I'm not sure that more would help, but I'll give it a try. Your avocado answer is fantastic btw. – Robert Mar 16 '17 at 8:36
  • Let us know either way and thanks :) – Jolenealaska Mar 16 '17 at 9:42
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    Like wine give it less air space – paparazzo Mar 17 '17 at 10:56
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    Might it help to portion and freeze the juice? Many things store better in the freezer, though I have no information about carrot juice specifically. – Megha Mar 18 '17 at 1:25
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This is classic enzymatic-oxidation browning. Two main culprits - oxygen and a group of enzymes (polyphenoloxidases) that promotes a reaction between oxygen and polyphenolic compounds in the juice.

The juicing action will inevitably end up stirring into the liquid a lot of air which will end up dissolved in it. Air has 21% oxygen in it. Solubility of gases improves with lower temperatures. So, cold juice will hold more oxygen, and warm juice less. Unless you do your juicing inside a sealed cupboard filled with nitrogen, you will not be able to exclude oxygen from getting inside your juice. At lower temperatures, the enzymes become less active which will slow down the browning and counter the higher concentration of oxygen in your juice, but given enough hours, browning will still happen. You can try putting a barrier on the surface of the juice (a sheet of parchment or plastic for example) as soon as you finish juicing and before you put it in the fridge to prevent more oxygen from dissolving into the juice as it chills. It is unlikely to stop the browning.

You can restrain the enzymes by making the juice more acidic, with lemon juice for example, or vitamin C as suggested above (the key is pH not how much Vitamin C it naturally has) or citric acid. That would only slow down the browning and you might not like the altered taste.

You can deactivate the enzyme permanently by heat which means heating the juice to at least 65C, or better still, heating the carrots before juicing to well beyond 65C briefly. I suggest cutting the carrots into smaller pieces and putting them into a very hot water with any of the above acidic additives. I am sure heating will inevitably affect the taste, but it will stop the browning. It works with apples and pears. You can play with timing so that you destroy a certain amount of the enzymes, enough to have a good compromise between less browning and less taste change.

There are suggestions you find online such as freezing. You can freeze your juice, but again it would only slow down the browning a bit more, it will still happen given enough hours.

Other more extreme (and normally impractical) ideas include vacuuming the juice to extract dissolved gases from it, or using UHT and high pressure methods to break the enzyme.

I typically use 65C acidic water to blanche whatever fruit or vegetable, and I use a barrier on the juice surface before storing/chilling.

  • Since cold juice holds more oxygen than warm juice, would it be helpful to use warm carrots (I've been storing them in the fridge up till now) and wait until the juice is sealed to cool it down? – Robert May 13 '17 at 20:37
  • You can give it a try for sure. I did not see much difference between chilled and room temperature apples. It is always a trade off between dissolved gases and enzyme activity. At below 7C, enzyme activity is supposed to cease for browning but I have only experienced a slow down. Even at 3C in the fridge it still continues. Acidic blanching is the only method that worked well for me. – user110084 May 13 '17 at 21:18
  • I'll give acidic blanching a try, but it sounds like it's more trouble than just juicing a fresh batch every day, so probably not good for my specific use case. Thank you for this thorough and comprehensive answer! – Robert May 13 '17 at 21:21
  • You are very welcome @Robert. Try different methods. Reducing pressure with VacuVin may help too. If you find a way to use oxygen scavenging agents without getting the sachet wet, it may be worth a try too. This is cat-and-mouse sort of thing for sure. – user110084 May 13 '17 at 21:29
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juicing up carrots with a centrifugal juice extractor

This is very common for centrifugal juice extractors and one of the reasons why the juicers crowd prefers masticating juicers. Of course, the solution is not practical for everyone, and it does not completely prevent this type of browning and separation, but it does slow down.

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Based on Paparazzi's comment, I'd store it in a cleaned wine bottle and use a stopper/air-remover like a vacu-vin. That's a brilliant comment.

vacu-vin

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