Why do radishes turn from red to purple in MAP?


I am after some advice on radishes (red).  We have noticed that stored under MAP conditions - oxygen levels ranging from 10 to 15%, the radishes turn from a red colour to a purple colour over a 10 day shelf life.  Have you seen this before and do you know why this happens? (J.B.)


My assumption is that together with a drop in oxygen there is a rise in carbon dioxide. It is possible that a relative small shift in tissue pH, due to elevated CO2, would be responsible for a reversible change in anthocyanin pigments in the radish from red to purple. I do not have specific rates but I presume that it would require a fairly high CO2 concentration to accomplish this in 10 days.  I would start with getting some CO2 measurements. --Trevor Suslow