Where can I find out how food wrapping affects spoilage?

Some sources say that plastic and other wrappings actually speed up spoilage because they hold in air, but for the most part packaging slows food spoilage. The functions of packaging include acting as a barrier against microbial, physical and chemical protection.

Physical: - e.g. cardboard stops bruising of fruits, therefore preventing enzymic degradation of the flesh.

Microbial: Perhaps the most important aspect of food preservation. Packaging such as plastic or metal can prevent the entry and growth of microorganisms that break down food components and cause off smells and bad textures. For example, plastic wrapping over a half-eaten steak prevents entry of microbes that break down proteins and fats.

Chemical: Light and oxygen can causes damage to food by increasing the incidence of rancidity (e.g. autooxidation [fat breakdown]) and vitamin degradation (for example riboflavin in milk breaks down it the presence of sunlight). This is why most milk bottles are opaque and gas-impermeable, which means Oxygen can't come in. Another example is cellulose film wrapping of bread, which prevents staling by stopping sntry of oxygen.