Moisture transfer is the movement of moisture in stored products as a result of moisture and temperature gradients. In foods it causes familiar quality failures: soggy crusts on frozen pies, moisture migration from wet fillings into pastry shells, condensation inside packages that feeds mold, and freezer burn on poorly wrapped products. Packaging engineers and product developers control it with moisture-barrier films, proper temperature management that avoids freeze-thaw cycling, and formulation design such as humectant balance. Because uncontrolled transfer shortens shelf life and degrades texture, crispness, and safety, measuring and modeling it is a standard part of shelf-life testing.