- CHILLING INJURY IN TOMATO FRUIT 259
used as an indicator of physical damage of cell membranes in fruit,
including tomato (Saltveit 2005; Antunes and Sfakiotakis 2008; Zhao
et al. 2009; Dea et al. 2010).
IV. TIME–TEMPERATURE THRESHOLDS FOR CI SYMPTOMS
The “threshold temperature” of CI is defined as the lowest temperature
at which a susceptible fruit or vegetable can be stored with no symptoms
of CI ever developing (Brecht et al. 2012). The threshold temperature
for storing mature-green tomatoes is 13◦C (Hobson 1981). Below this
“threshold temperature,” it is possible that different low temperatures
result in different CI symptoms. For instance, the authors previously
demonstrated that mature-green tomatoes stored at 8◦C for 27 d showed
delayed (but not prevented) red coloration while fruit maintained at 6◦C
showed blotchy red coloration with occasional decay and those at 2.5◦C
showed a complete failure to ripen (red coloration), severe decay, and
loss of tissue integrity (Biswas et al. 2010, 2012a, 2014a). It seems that
there is a series of critical temperature thresholds at which different CI
symptoms are induced sequentially in tomato fruit.
A sequence of time-dependent events related to incremental chilling
damage at a given temperature has previously been reported. Tomatoes
stored at 4◦C for a period of time and subsequently returned to 21◦C
showed increased decay after 15 d, declined ethylene production after
27 d in the cold, and retarded red color development after 34 d cold
storage. Post-chilling evolution of CO 2 production still occurred in fruit
stored for as long as 39 d (Cheng and Shewfelt 1988). It was suggested
that a decline in structure and functionality of plasma membranes,
vacuoles, chloroplasts, and mitochondria occurred in decreasing order
of susceptibility to chilling temperature. Moline (1976) demonstrated
that at a given temperature (2◦C), chilling of fruit for 10 d interfered
with conversion of chloroplasts to chromoplasts. After 15 d, mitochon-
dria and plastids swelled and degenerated and after 21 d, organelles
were barely visible. Biswas (2013) found that tomatoes stored at 2.5◦C
showed altered red color development and increased ion leakage after
2 weeks and complete failure to develop red color and severe decay
by 4 weeks. These results suggest that at a given chilling temperature,
there is a sequence of chilling-induced damage incurred by different
organelles.
Metabolic activity of the fruit is directly but differentially influenced
by low temperature also. Kinetic parameters of enzymatic reactions
are known to be temperature dependent. Low temperature can affect