(1) Importance of type of light. Not all wavelengths making up natural or
artificial light are equally absorbed by food constituents, nor are they equally
destructive. Surface discolorations of sausages and meat pigments are different,
depending upon the natural light and fluorescent light that may be encountered in
(2) Control techniques. Sensitive foods often can be protected from light by
impervious packaging or by incorporating compounds into glass and transparent films
that screen out specific wavelengths. A related problem has to do with maintaining the
true color of inks used to depict products in food advertising and on food product labels.
(3) Greening of potatoes. Another problem due to light is the greening of
potatoes. This condition is also referred to as sunburn. It is the result of the exposure
of the potatoes to sunlight during growth or after digging, and to artificial light during
display for sale. After exposing for two days or longer to either natural or artificial light,
a green pigment develops. The skin and the flesh are affected. Chlorophyll and an
alkaloid called solanine are produced due to exposure to light. The green tubers
acquire a bitter, pungent taste. If eaten in quantity, they may be poisonous. Solanine is
the bitter and poisonous component. Chlorophyll is tasteless and harmless.
Another major cause of food deterioration is that of time or the aging process.
a. Peak Time for Quality. After slaughter, harvest, or food manufacture, there
is a time when the quality of food is at its peak, but this is only a transitory period. The
growth of microorganisms, destruction by insects, action of food enzymes,
nonenzymatic interaction of food constituents, loss of flavor, effects of heat, cold,
moisture, oxygen, and light, all progress with time. The longer the time, the greater the
b. The Goal of Maintaining Freshness. It is true that certain cheeses,
sausages, wines, and other fermented foods are improved with aging up to a point.
However, for the vast majority of foods, quality decreases with time, and the major goal
of food handling and preservation practices is to capture and maintain freshness.
c. Storage Life. Time is considered an important cause of food deterioration,
for all foods have a definite storage life. The storage life is determined to a great extent
by type of food, method of processing, method of packaging, and storage environment.
However, the longer a food is stored, the greater is the opportunity for deteriorative
changes to occur. This is the rationale behind the frequencies of cyclic inspections of