- CHILLING INJURY IN TOMATO FRUIT 263
species, although it is not always a good indicator of overall sensitiv-
ity to chilling. While those factors (cultivar, preharvest growing condi-
tion, or stage of development) can influence time–temperature thresh-
old bar for a symptom, is it possible that they can alter sensitivity of each
symptom differentially, causing a different sequence of symptoms to
appear?
Although the initiation of secondary events may appear sequentially
and different low temperatures induce different CI symptoms, it is not
obvious whether this is a result of a different time–temperature thresh-
old for damage or just that the phenotype takes longer to display that
damage. For example, underlying damage for the initiation of blotchy
red coloration may occur at a particular time–temperature threshold
level, but the phenotype can only be seen after a certain time. Until color
begins to appear during ripening, it is impossible to detect unevenness
in that color. Chomchalow et al. (2002) noticed that there was an appar-
ent shift from no chilling injury (blotchy red coloration) after 1 or 3 d
to injury after 5 or 7 d at 7.5◦C. The same could be true for describing
increased ion leakage as an indicator of chilling damage. Saltveit (1989)
found that chilling did not immediately increase the rate of ion leakage
from tomato pericarp discs; rather it caused a progressive increase in
permeability over a few days of chilling.
Chilling-sensitive fruit develop a series of symptoms and each symp-
tom has an independent time–temperature threshold to appear. Con-
sumer perception of “critical threshold level” may, however, change
in a commercial situation depending on socio-economic or cultural
consumer attitudes. For instance, loss of flavor is an important qual-
ity attribute for consumers from high-income affluent households but
not necessarily for consumers coming from poor socio-economic con-
ditions. For them, having a red color tomato may be more important
than tomatoes of good red color with high flavor. The commercial con-
sequence of varying thresholds for time–temperature-dependent initi-
ation of CI symptoms is possibly different in different markets. Here
tomato is just an example; it could also apply for other chilling-sensitive
crops. In addition to consumer segregation, the concept of threshold
time–temperature for a CI symptom may vary depending on the indus-
try such as between the fresh tomato and the processing industry. For
instance, tomatoes with pitting or chilling-induced “mild” texture alter-
ation can be presumably processed without overall quality (inhibition
of red color development, induction of mealiness) being compromised
and, therefore, those tomatoes can be stored for an extended period
before processing.