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Questions on oxidation and ascorbic acid

Hi all - first 'proper' post here!
 
First off, I have spent quite awhile reading through old threads, which has informed me enough to ask the following questions.  I made a new thread rather than dragging up a number of old ones, hope that's cool.
 
I've got a sauce I've been making for quite a while now (years), and its reached a point where I'm trying to apply the finishing touches.  One of the slight niggles I have with it is that it slowly changes color over a prolonged period, like 6 months or more.  It starts off a deep and fairly bright purple/red, its quite a striking color which people always comment on.  But it slowly loses the brightness and the purple/red becomes more of a brown/red.  It doesn't actually look bad, but it's not as striking as when it was fresh.  If the sauce is refrigerated or unopened or opened very little, the effect is not so noticeable, but in a bottle that is not refrigerated and frequently used, it is much more noticeable.  A friend of mine swears the taste deepens as it changes color as well, to me the taste definitely deepens over the first week but after that I'm not so sure personally, but I do trust him and he's had quite a lot of the sauce and he also consumes it at a much slower rate than me.
 
The sauce is not fermented, it consists of roasted ingredients - peppers, onions and garlic plus a relatively small amount of citrus simmered with a fair amount of fresh, non-roasted mango plus some dates - then blended.  I have not tested the PH using a proper tester, but ph test strips (crude I know) put it in the 3 or 4 sort of range.  It does seem to last indefinitely either refrigerated or not.  
 
So - I'm guessing the slow browning is caused by oxidation, particularly the mango would suffer from this I'd guess.  But definitely interested in hearing any other thoughts on it.
 
Assuming it is oxidation, I gather that ascorbic acid should help, and this is where my questions come in:
 
Would ascorbic acid totally halt this process, maintaining the original color indefinitely - or merely slow it down?
 
Will ascorbic acid affect the flavor?
 
Is all ascorbic acid the same?  Stupid question maybe but the reason I ask is the prices I've seen online vary wildly...
 
How much ascorbic acid should be added?  I've seen a suggestion in a different thread of 1/4 tsp per pint - does this sound reasonable?
 
And finally - assuming the flavor does develop over a period of months, is this also caused by oxidation, or is it a separate process?
 
Thanks in advance for any help!!!
 
IDK.

but i got to reading... apparently free oxygen is just a small part of the issue with color stability.

apparently if your food emulsion has extreemly tight interfacial tension... your long complex chromophore bio molecules can be held or bent in such a way that their electron cloud gets delocalized and oxygen atoms are better able to react with shit, and bonds are better able to be attacked by UV light etc.


http://hss.ulb.uni-bonn.de/2002/0112/0112.pdf

i would figure out what it is exactly thats fading... then research how to prevent that chemical from fading.
 
dragonsfire said:
People have used Vitamin C and E to preserve foods, natural versions, I think it more trial and error depending on whats in the mix.
 
 
It should have quite a lot of Vitamin C in it already, but apparently not enough (based on my current hypothesis anyway) so I was thinking that some pure vitamin C might do the trick without drastically changing the sauce.  But, having looked up vitamin E I see it is an anti-oxidant, so maybe there is something in that.  Most results I see for it though are oils to rubbed on skin, so that will require some more looking in to.
 
 
queequeg152 said:
IDK.

but i got to reading... apparently free oxygen is just a small part of the issue with color stability.

apparently if your food emulsion has extreemly tight interfacial tension... your long complex chromophore bio molecules can be held or bent in such a way that their electron cloud gets delocalized and oxygen atoms are better able to react with shit, and bonds are better able to be attacked by UV light etc.


http://hss.ulb.uni-bonn.de/2002/0112/0112.pdf

i would figure out what it is exactly thats fading... then research how to prevent that chemical from fading.
 
Ok so that's quite interesting, I should have figured there'd be more to it, so I'll start by having a look at that, might take me a bit though, haha.  But yeah that's a very good point, I don't actually know what it is that's fading much less why.  I'll get on it though, my intention is to fix up a new batch imminently, so it would be good to test out a few solutions in the process.
 
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