Re: How come Orange Juice tastes so awful right after you brush your teeth?

I doubt that there is a chemical reaction between orange juice and
toothpaste. Rather, if there is anything at all happening it may (?)
be that brushing your teeth cleans all that yuckie placque off and some
of it is still around. Also brushing your teeth may stimulate the taste
buds on your tongue (do you brush your tongue occasionally - you should).
Orange juice is of course rather acidic and can
taste quite tart.  Taste, bitterness, etc will vary a lot from batch
to batch even in frozen and canned oj.  You might try brushing your
teeth after breakfast instead of before.  That way you have clean teeth
for a longer time (until lunch or your next snack) and avoid the
oj/toothpaste/brushing problem all together ;-}