The temperature was not cold enough to freeze the food.
To freeze food, set a temperature of -18 °C or below. Use the SuperFreeze function (if applicable) to freeze your food in such a way that it is preserved better.
If food is frozen quickly, the cells have less time to lose moisture, so they shrink significantly less. As there is not so much moisture loss, it is easier for the food to reabsorb it during the defrosting process.
