- CHILLING INJURY IN TOMATO FRUIT 253
phytoalexins, or the capability of wound healing and strengthening of
the cell wall by formation of glycoproteins, callose, lignin, and other
phenolic polymers. Nevertheless, if fruit tissues have already become
“weak” because of harvest-related wounding and improper temperature
management, they may be too vulnerable to resist pathogenic attack.
D. Loss of Aroma and Flavor
Uneven blotchy red coloration, complete failure to develop normal red
color, abnormal texture, and increased decay susceptibility are all gross
CI symptoms, whereas loss of aroma and flavor reflect subtle chilling
damage symptoms that are nonetheless important in terms of quality. It
is generally believed that ripe tomatoes purchased from supermarkets
are “nice red in color” but lack the desirable “tomato-like” flavor com-
pared to ripe tomatoes picked directly from the home garden or field
(Buttery et al. 1987; Baldwin et al. 2008). Tomato breeders have made
substantial progress in achieving cultivars with higher yield, improved
visual characteristics, greater disease resistance, larger fruit size, and
firmer fruit (Maul et al. 2000; Tieman et al. 2006). However, sensory
qualities of aroma and flavor have been neglected over time. Complex-
ity of aroma and flavor traits and the large number of genes involved
contribute to these attributes which may be reasons for not having
received research emphasis in the past (Mathieu et al. 2009). However,
the development of molecular tools offers new opportunities to under-
stand and introduce genes that enhance aroma without compromising
other important traits (Galili et al. 2002).
Sugars, acids, and their interactions are important to sweetness, sour-
ness, and overall flavor intensity in tomatoes (Stevens et al. 1977; Bald-
win et al. 2008). Storage temperature plays a significant role in main-
taining aroma and flavor of tomato (Kader 1986) with low temperatures
altering the ratio of sugars and acids (Hall 1968) and changing perceived
flavor (Maul et al. 2000). Accumulation rates of citric acid and acetic
acid increased as storage temperature was reduced but decreased at a
higher temperature (19◦C) (Thorne and Efiuvwevwere 1988). Mature-
green fruit stored at 2◦C for 14–21 d (Kader et al. 1978) or breaker fruit
at 6◦C for 27 d (Gomez et al. 2009) had lower concentrations of glu- ́
cose and fructose than non-chilled fruit. Thus, lower flavor intensity
of cool-stored tomatoes may result from higher acidity and/or lower
sugar concentration. Since mature-green tomatoes have a lower sugar–
acid ratio than those harvested at the ripe stage (Moneruzzaman et al.
2008), it is not immediately obvious if alteration in the sugar–acid ratio
following low temperature exposure reported by these researchers