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If I keep fresh vegetables in the fridge, how quickly is vitamin C lost? What is the rate of loss in percent per day, or any other relevant measure?

  • Hello Joshua. The question hasn't been asked, because nutrition is mostly off topic here. We do deal with a very limited range of nutrition questions, but you'd have to be very specific. We never do "nutrients" in general, because different people care about different substances. I edited your question to be specifically about vitamin C only, else it would have been closed. But I'm not sure you'll get an answer even now. – rumtscho Sep 12 '14 at 8:31
  • I was reading this prior and during the edit, and witnessed both versions. I'm not sure the edited version holds true to the original intent. @Joshua - please clarify. – Michael E. Sep 12 '14 at 8:39
  • Here is my question: I know that Vitamin C is lost through contact with air and heat. (but since we are dealing with fresh vegetables here, heat is out of question here) But what is the RATE of this loss? Like, 20% every day, etc. Thanks again – Joshua Sep 12 '14 at 9:22
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    Vitamin C is not lost, there is no magic happening, it is just consumed by cells trying to protect themselves from dying. You typically see a 50% reduction within 7 days, and then the loss rate reduces as the cellular processes stop. For many vegetables the loss rate is much less if kept chilled. Most food books that publish vitamin C levels do so at X days after harvest, to simulate the normal farmer to consumer process (check the fine print). Either way a normal balanced diet will provide way more vitamin C than required with 7 day old vegetables – TFD Sep 12 '14 at 9:23
  • That was the answer I was looking for :) Thanks a lot, Also, any sources/articles related to Vitamin C loss is highly appreciated – Joshua Sep 12 '14 at 9:27
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To put it simply, it's lost exceedingly rapidly. Can we scientifically measure the exact amount of the reduced form of vitamin C in produce over time? Yes, we can. Have there been studies and papers published that have done this? Yes, there have been. Are these results relevant? Yes and no.

These results allow us to draw certain conclusions about the loss* of vitamin C after produce has been harvested. We know that plant cells are constantly biosynthesising vitamin C (through a chain of biochemical reactions involving glucose) and at the same time using it in oxidative processes. By harvesting crops we're taking away a part of this natural oxidative loop and plant cells begin oxidative changes leading up to oxidative stress. The results of these studies confirm the theoretical knowledge we posses about oxidative cell cycles but there is no deterministic way we can deduce or even estimate with high precision the exact percentage of vitamin C that gets used up in the processes we observed. The loss rate is too specific to individual crops and the conditions in which it was harvested and since preserved. You could try to extrapolate the results of such studies (as the one linked below) to the produce you keep in your fridge but you would most assuredly get highly varying results.

*Please note that vitamin C is not lost, it is just transformed into a different form (oxidative form) during the oxidative processes that take place inside plant cells.

What we know for sure is that by reducing the temperature we slow down the oxidative processes that change the plant cell's biostructure, molecules and function. We can take cold inhibition to an extreme by deep freezing produce which virtually stops these deteriorating processes.

This answer has already run a bit longer than I originally planned but I thought giving you some background to the biochemical processes that take place might be useful. Lastly I'd like to give you a practical example of exactly how vitamin C oxidation (even visually) deteriorates produce.

Half an apple, where the left side has been artificially treated with vitamin C: Half an apple, where the left side has been artificially treated with vitamin C:

Relevant links: (1)

  • Thanks for the informative comment, Looking at the picture can we say that if a color is retained, vitamin c is mostly there? For example i can keep herbs like parsley and dill in cool airtight bags wrapped for a week after which they have their full color, can we imply that vitamin c losses have been minor? – Joshua Feb 27 '15 at 0:14
  • @Joshua No, unfortunately, we can't make such an implication as the discolouration is not solely attributed to vitamin C oxidation - the produce could look great and have a low reduced form vitamin C content, but it can also look poorly and have a high reduced form vitamin C content. It's virtually impossible to tell without doing a full scientific study per harvest (produce from the same harvest will most likely 'lose' vitamin C at approximately the same rate). – dijkstra Feb 27 '15 at 16:20
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Vitamin C is not lost, there is no magic happening, it is just consumed by cells trying to protect themselves from dying

You typically see a 50% reduction within 7 days, and then the loss rate reduces as the cellular processes stop

For many vegetables the loss rate is much less if kept chilled. Most food books that publish vitamin C levels do so at X days after harvest, to simulate the normal farmer to consumer process (check the fine print)

Either way a normal balanced diet will provide way more vitamin C than required with 7 day old vegetables

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It is lost quickly! As soon as it is picked, it begins to lose C, but I don't know at what rate. Heat and light affect the loss. Long ago I read a study about how fast oranges lost their C and why frozen O.J. may actually have more C - it is often processed faster and flash-frozen whereas an orange may sit around a week or two before being eaten. The study showed that the orange lost about 10% of C within the first few hours of being picked.

  • I've removed a little of your answer which discussed health issues; health is off topic here. – Cascabel Nov 23 '14 at 7:10

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