Alan was following an old recipe to produce some sort of fermented apple concoction. The recipe called for apple juice. Alan purchased a bottle of organic apple juice. According to the label, there was nothing in it but organic apples. Yet it killed the microbes. Several times this happened. Alan then called the manufacturer, and after questioning he discovered that ascorbic acid had been added to the organic apple juice as a preservative because it kills bacteria and is cheap. Unfortunately, it does not simply kill bad bacteria, for it gets the good, the bad and the ugly.

This goes back to what I have been trying to tell people for years.  Acidity kills most microbes, alkalinity makes them thrive.

And as much as I hate synthetic vitamin C and especially megadosing of the crap the claim is somewhat misleading.  The guy was adding the vitamin C (ascorbic acid directly to the bacteria making the environment too acidic for them to survive.  Ingesting ascorbic acid is different.  It is like how people say if you ingest acidic lemon juice it is going to go alkaline in the body. It is mote really going alkaline per se.  As the acid leaves the stomach there is a bicarbonate release from the pancreas, which neutralizes most if not all the acidity.  Ascorbic acid will also be buffered as well unless the acidity of the ascorbic acid exceeds the body's buffering capacity.  So the first thing that would have to be established is that the ascorbic acid is arriving intact to the colon where most of the flora is.  The answer to this is highly unlikely. Even if the ascorbic acid survives the bicarbonate buffering there is still another problem.  Synthetic vitamin C is extremely unstable.  Back in high school we took synthetic vitamin C crystals and exposed samples to light, heat and moisture.  In all cases the synthetic was completely destroyed with 40 minutes.  So the destruction of the ascorbic acid begins immediately as soon as you down it with water.  And to go from the stomach to the colon takes much longer than 40 minutes.  So it is would be about impossible for any of the unabsorbed synthetic ascorbic acid to reach the colon, where most of the flora resides, intact.

But there is still more to this.  As excess ascorbic acid breaks down it forms another acid called oxalic acid.  Oxalic acid is a very strong tissue irritant and it also binds minerals such as calcium preventing the body from utilizing them. How this will affect the body depends in large part on whether or not the excess ascorbic acid is absorbed.  If absorbed, the oxalic acid formed from the breakdown of the ascorbic acid will bind calcium in the blood and will be excreted through the urine. This is why ascorbic acid can lead to UTIs and increase the risk of calcium oxalate stones in some individuals.  If broken down in the intestines the oxalic acid will bind to calcium in the intestines preventing its absorption.  The oxalic acid can also irritate the intestinal tissues leading to inflammation, water release and increased peristalsis leading to diarrhea.

Back to the original point though.  How something reacts when directly applied to living cells does not mean this will happen in the body.  I give an example of this with the researcher's claim that Saint Johnswort causes infertility in this post:

http://curezone.org/forums/fm.asp?i=1525662#i