- CHILLING INJURY IN TOMATO FRUIT 257
maturity stages (pink or ripe stage) compared with non-chilled fruit,
as reported by Maul et al. (2000) or Boukobza and Taylor (2002), it
can be argued that this is a direct result of chilling. Nonetheless,
aroma development is by no means complete when tomatoes are har-
vested at breaker or pink stage and low temperature storage can cause
delayed ripening in tomatoes even when harvested at advanced matu-
rity stages (Gomez et al. 2009). Therefore, reduced concentrations of ́
aroma compounds in chilled tomatoes may not be a result of a direct
effect of chilling but could be a function of delayed ripening. Using
red ripe tomatoes, Farneti et al. (2015) found that volatile production
went up on post-chilling transfer to higher temperature (22◦C), but
the concentration was lower than in the fruit continuously stored at
room temperature, indicating a direct effect of cold storage on tomato
flavor.
E. Increase in Ion Leakage, Indicator of Membrane Damage
An increased rate of ion leakage in tissues is often correlated with
appearance of CI symptoms and measurement of CI severity in many
crops including tomato (Lafuente et al. 1991; Cotˆe et al. 1993). The rate ́
of increase in electrolyte leakage varies with season, crop, and also with
cultivar (Kuo and Parkin 1989; Saltveit 2005). An enhancement in elec-
trolyte leakage was reported in tomato (“Castlemart”; harvested in sum-
mer) pericarp discs chilled at 2.5◦C after 3 d (Saltveit 2002). However,
pericarp discs from the same cultivar harvested during winter exhib-
ited an increase in electrolyte leakage only after 6–7 d at 2.5◦C (Saltveit
2005).
Chilling does not immediately increase the rate of ion leakage from
tomato pericarp discs, rather it causes a progressive increase in perme-
ability over a few days of chilling (Saltveit 1989). In cucumber stored
at 4◦C, irreversible damage resulting from chilling required 7–10 d
as indicated by increased tissue electrolyte leakage (Kuo and Parkin
1989). Since several days of chilling were required for leakage rates to
become significantly greater than for the non-chilled control (Saltveit
2002), it suggests that the phenomenon may not be a direct result of an
abrupt temperature-induced “phase transition.” If phase changes were
the direct cause of chilling-induced leakage, changes in membrane per-
meability should be rapid and leakage should be detectable within a few
minutes of chilling. Nonetheless, it is possible that underlying damage
in cellular membranes could occur because of the initial abrupt lipid
phase transition after an exposure to low temperature, but the signifi-
cant increase in ion leakage may take longer to display. Interestingly, in