Preservation and Isolation: Aluminum foil can effectively block air, moisture, light and odors. It is often used to wrap food and seal the openings of containers to extend the shelf life of food and prevent cross-contamination. For example, takeout boxes, chocolate packaging, milk powder cans, and sealing closures. 

Baking and Barbecuing: When baking and barbecuing, aluminum foil can be used to wrap the ingredients (such as grilled fish, grilled sweet potatoes, vegetables), locking in moisture and preventing the food from burning directly against the flame or the baking pan. It also allows the seasonings to be evenly distributed. It can also be placed on the baking pan for easy cleaning. 

Freezing storage: Used for packaging frozen foods such as meat and seafood to prevent drying out and cross-contamination. 

Aluminum foil is widely used in food packaging and cooking. This is mainly due to its properties such as barrier effect, heat conductivity, softness and non-toxicity. 

Food packaging application 

Barrier protection: Aluminum foil is highly effective in blocking air, oxygen, water vapor, light, grease and odors, which is crucial for maintaining the freshness, flavor and nutrition of food. It can prevent food from oxidizing and deteriorating, getting damp and moldy, or losing its aroma. 

Composite packaging materials: When the pure aluminum foil is thin, it is prone to damage. Therefore, in food packaging, the commonly used material is a composite film, which combines aluminum foil with plastics (such as PE, PET), paper, etc. This composite material retains the excellent barrier properties of the aluminum foil while enhancing its strength, toughness and printing performance. 

Common application forms: 

Soft packaging bags: Such as those for milk powder, coffee, tea, nuts, meat flake, and instant noodle seasoning packets, etc., are usually made of aluminum-plastic composite film and can preserve food for a long time. 

Dining box lid: The inner side of the lids of many takeout boxes (especially foam boxes or PP plastic boxes) has a layer of aluminum foil, which serves the functions of sealing and maintaining heat. 

Drug/health supplement packaging: Such as the backboard of the blister packaging (PTP) mentioned earlier, as well as the moisture-proof packaging for capsules and tablets. 

Preservation sealing: In supermarkets, above the trays of some unpackaged foods or cooked foods, there is a layer of aluminum foil covering them. This is used for temporary preservation and to prevent contamination. 

2. Cooking Applications 

Baking: 

Lock moisture and maintain hydration: Wrapping food (such as grilled fish, grilled chicken, potatoes, sweet potatoes, vegetables) can prevent water loss, keeping the inside of the food tender and juicy, while avoiding burning due to direct contact with high heat. 

Uniform heating: Helps to distribute the heat more evenly throughout the food. 

Preventing dripping: During the baking process, you can catch the grease and juices that seep out from the food to prevent them from dripping onto the bottom of the oven, which could cause smoke and make cleaning difficult. 

Adding flavor: Before packaging, you can add spices and sauces to allow the food to fully absorb the flavors in a sealed environment. 

Covering the baking tray/container: When baking cakes or bread, if you notice that the surface is coloring too quickly, you can cover it with a layer of aluminum foil to slow down the coloring process and prevent burning, allowing the interior to continue to cook thoroughly. 

Grilling: Similar to a oven, you can wrap foods that are not easily cooked or fragile (such as shrimp, shellfish, chives, eggplant slices) with aluminum foil and place them on the grill. This way, the food can be prevented from falling off and it will be heated evenly. 

Thermal insulation: For freshly cooked food, it can be wrapped in aluminum foil. The reflective property of the foil helps to retain some heat, providing a certain degree of insulation. 

Simple cooking utensils/containers: You can temporarily fold aluminum foil into small bowls and spoons (be careful not to touch the open flame directly) to hold food or seasonings. 

Cleaning Aid: Placing a layer of aluminum foil on the baking tray can significantly simplify the subsequent cleaning process. 

Usage Notes 

Acidic foods: If acidic wet foods (such as tomato sauce, foods pickled with lemon juice) are wrapped in aluminum foil for a long time, a small amount of aluminum may dissolve. Although it is generally believed that the amount is very small and harmless, for safety reasons, try to shorten the contact time. 

Sharp objects: Aluminum foil is prone to being punctured by sharp objects. Be careful when using it. 

Microwave oven: Never put aluminum foil in the microwave oven for heating. Metal will reflect microwaves, which may cause sparks or even damage the microwave oven. 

In summary, aluminum foil is not only an excellent passive protective barrier in the food industry, but also a practical active cooking tool.