How come when you first open a package of hot dogs there is no liquid inside, but by the next day . . .?!
Answers: when you open the package again, there is all kinds of liquid in the package?
that liquid is mostly salty water. What happens is after some time in a package the hot dogs which contain cooked meat protein gradually lose there water holding capacity. The protein is denatured already. So as the lose the ability to hold water (something like a sponge) the water gets expressed in the package. Technically the term is syneresis.
PhD Food Chemistry and Nutrition
Edit
thanks. glad you liked my answer. I try to deal with facts not nasty rumors.
that is the nasty juice from all the disgusting things they grind up into a mush b-4 squeezing it out a tube into the shape you see b-4 you , think of it like this : imagine all the things you see in the grocery store that you would never eat , like chitterlings , tongue , pigs feet , etc. now imagine all the other parts of an animal you have not seen for sale in a store , that's what is left over + it gets made into hot dogs . eyes + teeth , lips , etc.