- CHILLING INJURY IN TOMATO FRUIT 233
exposure, and sensitivity of the species to that low temperature (Saltveit
and Morris 1990). Crops are generally able to recover from brief expo-
sures to chilling temperature and function normally once low tempera-
ture stress is removed. However, if exposure of sensitive species to low
temperature (below a threshold level) persists for too long, it causes
metabolic dysfunction, and irreversible manifestation of visible symp-
toms (Lyons 1973). Rate of development and magnitude of the visible
symptoms of injury depend, to a large extent, on tissue type, variety,
metabolic status of the tissue at the time that chilling stress is imposed
(active or dormant), and on a variety of environmental factors (Bramlage
and Meir 1990).
Development of CI may occur during exposure to low temperature,
but the symptoms usually appear after transfer of a product to a
warmer, non-chilling temperature (Cheng and Shewfelt 1988). Some
CI symptoms are qualitative in nature, including developmental or
metabolic disorders such as incomplete or inhibited ripening, excessive
or inhibited softening, and deficient aroma and flavor. Physiological
symptoms become apparent in different ways including skin depres-
sion (pitting), abnormal skin yellowing, tissue decomposition, internal
or surface browning, woolly or dry pulp texture, and fungal or bacterial
rot (Saltveit and Morris 1990). Some disorders may affect the skin of the
produce but leave the underlying flesh intact; others affect only certain
areas of the flesh or the core region (Wills et al. 2007). CI symptoms are
sometimes characteristic of a particular crop such as woolly texture in
peaches and nectarines, sunken patches on citrus, superficial scald of
apple, or abnormal color development of tomato fruit.
A. Possible Mechanism of Inducing Chilling Injury
Many theories have been proposed to explain the primary mechanism
of CI and subsequent development of its symptoms (Saltveit and Mor-
ris 1990). While CI has been recognized, described, and studied for over
100 years (Molisch 1896 as cited in Lyons 1973), the exact mechanisms
of this disorder and its effects are not completely understood (Sevillano
et al. 2009; Vega-Garc ́ıa et al. 2010; Luengwilai et al. 2012; Sanchez-Bel
et al. 2012; Cruz-Mend ́ıvil et al. 2015). Given all the variables of induc-
ing CI, the variety of horticultural crops and their diversity in morpho-
logical structure, composition, and developmental stage, understand-
ing of the CI problem is not simple and it is no surprise that numerous
reports have been published in an attempt to understand and clarify
this phenomenon.
Cell membrane damage and disruption of membrane integrity under
low temperature stress is thought to be the primary cause of CI (Wang