Light is the least understood enemy of food storage. Exposure to light can cause foods to spoil faster. Both natural and artificial light can cause photodegradation, according to the Department of Food Science and Human Nutrition at Clemson University. Exposure to sunlight, fluorescent light or incandescent light can cause photodegradation.
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 from the food;
- length of exposure;
- optical properties of the packaging materials;
- Whether the food is solid or liquid.
Light normally penetrates only the outer layer in a solid food, typically causing discoloration on its surface. Light can penetrate liquids more deeply and affect more constituents because of mixing and agitation.
When foods and spices like chili powder, which are normally brightly colored, have faded, their flavor and nutrient content have decreased. Deterioration from light exposure effects light sensitive constituents, like those listed below.
- Vitamins — Vitamin A, Vitamin B12, Vitamin D, Folic Acid, Vitamin K, Vitamin E, Pyridoxine, Riboflavin
- Pigments — Anthocyanins, Carotenoids, Chlorophylls, Myoglobin, Hemoglobin
- Amino Acids — Tryptophan, Phenylalanine, Tyrosine, Histidin
- Fats — Unsaturated fatty acids, Phospholipids
According to the University of Minnesota, the riboflavin content in enriched macaroni has been known to drop by 33 percent after exposure to light for one week. Oils and fats seem to be practically sensitive to the effects of light.
Wet pack foods in metal cans do not need to be protected from light. Food in glass jars will need protection. Special care should be taken with home canned food in mason jars. They should be store in dark rooms, containers or cardboard boxes. The boxes the jars come in work well.
Dry foods packed in plastic buckets should be kept out of bright lights, unless the contents are packed in Mylar bags. Personally, we try to keep all our foods in dark cool dry and insect free areas.