236 Produce Degradation: Reaction Pathways and their Prevention
8.6.4 STORAGE
Storage conditions (temperature, atmosphere, relative humidity) are critical for main-
taining the nutritional quality of fruits and vegetables. Handling produce at high
temperatures enhances the loss of heat-sensitive nutrients, particularly vitamin C,
but also other components such as carotene, chlorophyll, and lycopene. The storage
of produce at too low temperatures may also cause nutrient loss as a result of chilling
injury. Thus, storage at too high or too low temperatures can decrease the nutritional
and market quality of produce. The delay in cooling of some produce has also been
reported to impair the physical appearance and biochemical processes (Nunes et al.,
1995). Storage conditions may also enhance degradation processes such as transpi-
ration, respiration, and degreening. Therefore, it is imperative that adequate storage
conditions be maintained from harvest until consumption.
8.6.5 PROCESSING
Processing conditions may affect the nutrient quality of fruits and vegetables by
enhancing losses of vitamins and minerals. Thermoprocessing of fruits and vegeta-
bles, for example, results in significant losses of vitamin C, thiamin, and vitamin A
activity (Salunkhe et al., 1991). Light or minimal processing of produce such as
fresh cutting makes the produce highly perishable because a large proportion of the
surface area is exposed. If storage conditions such as temperature, atmosphere,
relative humidity, and sanitation are not maintained during processing of produce,
significant losses of physical, chemical, and market qualities occur (Watada et al.,
1996). In some studies, significant losses of vitamin C were observed in stored fresh-
cut potatoes, butterhead lettuce, and spinach (Varoquaux et al., 1996; Tudela et al.,
2002; Evelyn et al., 2003).
8.6.6 PACKAGING
Packaging of fresh produce is important because it controls the atmosphere sur-
rounding the produce (Watada, 1987; Watada et al., 1996; Watada and Qi, 1999).
Proper packaging slows down the degradation processes of transpiration and respi-
ration. Packaging also provides sanitary conditions for produce and minimizes the
need for use of disinfectants (Zhang and Farber, 1996). When fruits and vegetables
are packaged in permeable polyethylene bags, the relative humidity in the surround-
ing atmosphere increases, leading to a decrease in transpiration. Water loss is rapid
at low relative humidity (RH) and slower at higher RH because the air in the room
contains less water vapor than it can hold at the prevailing temperature. Thus, water
vapor is readily transferred from the humid interior of the fruits and leafy vegetables
to the relatively dry air. Excessive transpiration causes loss of water-soluble nutrients
such as some vitamins and minerals and weight of the produce, which are important
for market and nutritional value. Packaging also protects the produce from rapid
evaporation caused by a high velocity of air circulating in the storage rooms (Zagory,
1999).