Almost all foods are exposed to light from natural and/or
artificial sources. The exposure of foods to light can result in
the photodegradation (or spoilage) of these products. This
photodegradation usually occurs in food constituents, such as
pigments, fats, proteins, and vitamins and results in
discoloration, off-flavor development, and vitamin losses. The
light that is absorbed by the food can cause deteriorative
reactions of the food constituents. In most solid foods, the light
only penetrates the outer layer of the product and photodegradation
occurs in this surface layer. Discoloration on the surface of foods
can certainly affect consumer acceptance of these products. In
liquid foods, light penetration can be greater and with mixing of
the products due to agitation, larger portions of food constituents
may be deteriorated. The light sensitivity of a food depends on
many factors including the: light source strength and type of light
that it emits; distance of the light source form the food; length
of exposure optical properties of the packaging materials; oxygen
concentration of the food; and the temperature. The information
found in this backgrounder was adapted from a series of fact sheets
developed by Dr. Robert Gravani, Cornell University