In the UK at present, one of the examination boards has set a "controlled assessment" (an experiment that pupils do at school under exam conditions) that involves testing a hypothesis that vitamin C is removed from fruit juice by heating it (i.e. in the pasteurisation process).
I am massively skeptical about this. The teacher guidance suggests "Treating fresh orange juice in boiling water for between 10 and 30 mins gives an easily measurable decrease in vitamin C levels". Leaving aside that this hardly represents a simulation of the pasteurisation process(!), does anybody know of any solid, academic studies of the effect of pasteurisation on the vitamin C content of fruit juice? I have tried (as a scientist, but non-biologist) my usual routes to reliable information and they fail miserably - the www is full of crackpots on this one.
As a follow-up to that, is it not the case anyway that the oxidation of the orange juice when it is boiled in this experiment, plus simple exposure to light could also be responsible for any decrease in vitamin C observed?