642 Produce Degradation: Reaction Pathways and their Prevention
A temperature of 13°C is recommended for slow ripening.^68 At this temperature
most cultivars can be kept in good condition for 2 to 6 weeks and change color very
slowly. At 15°C the rate of color change increases quite sharply, and above 21°C
the rate of maturation and other changes are increased. Tomatoes held at 18°C change
color rapidly without excessive softening. Temperatures of 21°C or higher induce
rapid ripening and bring about changes in color, softening, and flavor.
When tomatoes are fully ripe, the holding time can be increased by reducing
the storage temperature to 10°C.^67 Some experiments have shown that ripe tomatoes
can be held satisfactorily at 0 to 4°C. However, some softening may occur at 2°C.
Thus, it is generally considered detrimental to hold ripe tomatoes in cold storage
for more than a few days.
Maul and coworkers^67 found fruit stored for 2 d at temperatures below 20°C
was rated by trained panelists as significantly lower in ripe aroma and tomato flavor
than fruit stored at 20°C. Fruit stored at 5°C for 4 d was rated significantly lower
in ripe aroma, sweetness, tomato flavor, and significantly higher in sourness than fruit
stored at 20°C. The researchers associated the differences in sensory characteristics
with concurrent reductions in aroma volatiles measured by a gas chromatograph,
changes in chemical composition, and in scores during electronic nose evaluations.
Since many of these negative alterations in flavor and aroma parameters occurred
prior to the appearance of chilling injury symptoms, Maul et al.^67 proposed that
current recommended storage temperatures for tomatoes may be a prime contributor
to consumer dissatisfaction with commercially marketed tomatoes.
Holding tomato fruit at elevated temperatures inhibits the ripening processes.^69
If the high temperature is maintained too long, fruit will not ripen normally when
returned to temperatures of 20 to 25°C. However, if high temperature is held for a
week or less, fruits will ripen after a delay, thus extending shelf life.
The effect of exposing tomato fruit to high temperatures to induce tolerance to
chilling temperatures has been the subject of a great deal of research. Findings by
Lurie et al.69,70 indicated that heating tomato fruit to 38°C with 95% RH served not
only to reduce fungal rots and control insect pests but also decreased susceptibility
of the fruit to chilling injury. However, other researchers52,71,72 found that this high
temperature exposure lowered the quality of the fruit by inducing permanent unde-
sirable physiological changes. Whitaker^71 proposed that partial ripening of the fruit
at 20°C prior to cold storage was preferable to heat treatment for providing protection
from chilling injury.
20.5.8 FRESH-CUT PRODUCE
Minimal processing has been one of the hottest trends in produce marketing in the
last decade. Fresh-cut produce, defined as “any fruit or vegetable or combination
thereof that has been physically altered from its original form, but remains in a fresh
state,” offers the flavor, nutritional value, and freshness of fresh produce along with
added convenience.^73
Cut and packaged produce provides consumers with speed and ease of prepa-
ration. However, cut produce can be expected to behave differently from intact
product during storage due to its response to wounding and damage to the skin.^74