I have two questions
1) Some food containers contain a piece of tape that is used to keep the package closed. When one wants to use the package, he lifts up the piece of tape at the opening, and then retapes it when he is finished. Is this permissible?
2) I know that when opening food packages, one must avoid ripping letters or designs that are on the package. If one accidentally ripped them when opening the package, may he use the contents of the package on shabbos, or would it be prohibited due to ma’aseh shabbos?
1. Opening the tab for th first time is controversial, ( similar to the old disposible daipers, that there was controversy if it is considered korayah or not). therefore the tape should be opened and resealed before Shabbos. If it was already opened before Shabbos it is permitted to open then and reseal them because this seal is meant to be opened and closed often. If the bag was meant to be sealed for a specific amount of time, ( from one Shobbos to the next) then it is also problematic.
2. The food is permitted to eat becuse the ripping of the letters is not making the food ready to eat, as that part was only accidental.