I read a post on my friend John DiScala’s website, better known as Johnny Jet, about how to tell if your food has defrosted in the freezer. If it has, it’s not safe to eat after long trips.
Fill a cup of water and freeze. Then place a coin on top. Put the frozen water and quarter back in the freezer. Whenever you travel, check the cup upon your return. If the coin has fallen to the bottom of the cup, your food defrosted and needs to be composted or thrown out. If the quarter is on top, or even in the middle of the cup, your food is still fine.