Mason jars for the fridge or freezer-safe plastic containers for the freezer are my preferred method for keeping poaching liquid. If you plan on freezing your broth, make sure to leave at least ½-inch of head room. Frozen liquid will expand and you don’t want it to spill over. Another idea -- freeze poaching liquid in ice cube trays before storing it in the freezer. That way, if you need a little bit of broth for something like thinning out a pasta sauce, you can pull out one or two cubes without having to defrost the whole container.