Bags of suitable material can be used for semiliquid foods but are less convenient than rigid containers. They are well adapted to less moist foods. Sheets of freezer packaging materials are used for wrapping foods that hold their shape.
Bags and sheets are made of moisture-vapor-resistant cellophane, heavy aluminum foil, pliofilm, polyethylene, or laminated papers consisting of combinations of paper, metal foil, glassine, cellophane, or other materials.
Unwaxed folding cardboard cartons are often used to hold foods packaged in bags or sheets for protection against tearing and for easy stacking in the freezer. Sheets of packaging material may be used as outer wraps for unwaxed cardboard cartons containing unwrapped foods. The sheets are sealed with freezer tape, or with a warm iron if they are heat-sealing on both sides.
Ordinary waxed papers, household aluminum foil, and cartons designed for cottage cheese and ice cream are not sufficiently moisture-vapor-resistant to be suitable for packaging foods to be frozen and held more than a few days.
Head space. Since liquid expands as it freezes, allow ample head space when packing liquid and semiliquid foods. Most freezer containers have a mark or line to show how much head space to leave. For a tall, straight or slightly flared container and for bags, ½ inch is generally recommended for pints and 1 inch for quarts. For low, broad containers less head space is needed, about ¼ inch for pints and ½ inch for quarts. To assure a good closure, keep sealing edges free from moisture or food.
When packaging foods with freezer sheet material, wrap them as tightly as possible.
Sealing. Seal rigid freezer containers by adjusting the lids as required for the type of package used. Casseroles made of ovenproof material can be covered and then sealed with freezer tape or wrapped as needed.
Bags can be sealed by twisting and folding back the top and securing with a string or with a paper-covered metal strip or rubber band that may come with the bag. Some bags and sheets may be heat-sealed with a warm household iron or one of the special sealing irons available on the market. Others may be sealed with freezer tape.
Freezing
Freeze prepared foods as soon as they are packed. Freeze and store at 0° F. or below.