More on Vitamin C in English Apples
I was interested recently to be involved in a discussion forum on vitamin C in apples. Unfortunately halfway through our exchanges, the site stopped accepting my posts, so I'm putting a summary of them here.
M. wrote:
I have a number of desert apple trees and attempt to store the apples
in the garage during the winter.Many of the apples become soft, but still taste wonderful. In our family,we eat
lots of apples, both for their pleasant taste and to keep healthy. Does anyone know whether apples kept in this way
retain their vitamins (especially Vitamin C)?
This was followed by a reply referring readers to the vitamin C work on this site. 'M' read it, and replied as follows:
.....It's interesting to note that some apples, especially cookers such as Golden Noble,actually increase
Vitamin C in storage.
This misinterpretation of experimental 'scatter' attracted my attention, and I replied thus:
Dear M
I'm the person responsible for those vitamin C tests.
There's a lot of variability in vit c content in apples, but no
individual apple can increase its vit c content on storage. There's
just one way an apple might appear to contain more vit c per 100g -and
that's if it lost water (dried out) more quickly than the vit c
degraded.
I've found that vit c is retained most in acidic apples and those with
waxy skin. A picked apple loses vit c from the moment it's picked.
Those which retain it for longer tend to be the most acidic (though
not all acidic apples have much vit c to start with).
Vit C is, incidentally, completely absent in cooked apples. I could
detected none at all - not even in Bramley, which, when raw, contains
a high amount of this vitamin.
I found the vit. C content of most supermarket apples (raw bramley
excepted) to be negligible.
I'm not casting a slur on commercial apples- my analyses of these were on
stored, out-of-season fruit well past their best. The main factor in
vit C content, apart from variety, is freshness.
This attracted the following reply:
Hi Nigel,
Thank you very much for a fascinating post. I grow lots of
apple cultivars(50+) at my allotment and also have an orchard of
different cider apple cultivars, many quite rare.
Several of your
comments interest me. Firstly, your comment that vitamin c is absent
completely from cooked apples. Now I will enjoy my cooked apple,with or
a without a crumble topping,since it tastes extremely good. My children
tell me that my cooking apples (Golden Noble, Dumelow's Seedling, High
Canon, Newton Wonder, Norfolk Beefing, Emneth Early) all taste much better
than supermarket Bramleys, but that could be due to variety, not
freshness.
I was also interested in your comment that 'greasy' apples
keep their vitamin c better than others-however a nice desert apple
like Lord Lambourne becomes greasy quite quickly, but the acidic sharp
taste disappears within a month or so.
I also noticed that you tested
some cider apples e.g.Dabinett. It is traditional in cider making to
let the apples (particularly late bittersweets) store for a while to
soften and increase their sugar content - presumably this reduces their
vitamin c compared with the fresh apple. However, one does not make
cider particularly for the health giving properties of vitamin c, but
it would be interesting to know whether the traditional fermentation
process which takes the fresh pulp, presses it,and converts the sugar
to alcohol,actually retains the vitamins such as c.
M
My reply:
Dear M
Interesting to find someone asking questions about vitamin C. To follow up your questions: vitamin c is more delicate than other vitamins. It disappears more easily and is more rapidly degraded by cooking.
The vitamin c work was done with the help of an able young chemist, now at university, who carried out half the analyses. We did around five hundred titrations on about a hundred fruit in our first batch.
When we began getting results I was surprised that his vit C figures were always lower than mine. It was very puzzling; I watched him; he watched me, but we couldn’t see why our results weren’t the same. We were always out by a few percent, and his results were always lower. Finally I realised what it was – his analyses were slightly slower , and the vitamin was disappearing as we worked.
We modified our procedure to include a time element – and we did 4 to 5 analyses for each fruit instead of 1; the first - one min after grinding up the fruit, the second 3 min after grinding, another after 5min, and so on. In every case we found that the vit c level was falling, and smooth graphs could be plotted for vit c against time. A ground-up fresh bramley, for example, when dissolved in water, lost half its vitamin c in about 8 minutes. After 25 minutes, the vitamin had virtually gone. This surprised us; it does not seem to be documented anywhere. The pattern was repeated time after time, and we used the resulting graphs (over a hundred of them) to estimate what the vit c content had been at the start.
A few months later a company (I forget the name) was prosecuted when its apple juice was found to contain no vitamin c. we weren’t surprised.
I don’t know exactly what happens to the vit c, but it must involve reaction with air and must be influenced by the presence of substances from the fruit- probably enzymes which speed up the vit c loss. It’s interesting that pure vit c dissolved in water does not degrade like this. We analysed solutions of it; it lasted for weeks with no change in concentration.
I have not tested fermented juices, ciders, etc, for vit c. I suspect that the level is negligible. If anyone has personal experience of doing some measurements I would be interested to hear. The other vitamins will probably be present in about the same amounts as in the original fruit.
N.D.
compiled by Nigel Deacon / Diversity website
