Canning vs Freeze Drying. Canning uses heat and acidity to preserve food. Freeze drying removes water entirely. Water bath canning is for fruits, jams, and pickles. Pressure canning is for meats, soups, and vegetables. Freeze drying freezes food solid and uses a vacuum to sublimate ice into vapor. Canning is cheap and needs no power after sealing. Freeze drying costs more but lasts decades. | Rob Benson