I bought a bottle of pomegranate juice to make some grenadine for cocktails, and tried to freeze what juice I didn't use in ice cube trays. After a couple days in the freezer, the cubes are mostly frozen but still have thin layer of syrupy liquid on top. This same thing happened to me when I tried to freeze verjus earlier this year. My freezer temp is zero degrees Fahrenheit. What could be the problem? The label on the juice says it's 100% pomegranate juice from concentrate, reconstituted with water, zero added sugar.