Chilling injury

Fruit CI has been called endogenous brown spot, physiological breakdown, black-heart and internal browning, with the latter being more common (Plate 38). The symptoms of CI include: (i) wilting, drying and discoloration of crown leaves; (ii) failure of green-shelled fruit to yellow; (iii) browning and dulling of yellow fruit; and (iv) internal flesh browning (Lim, 1985; Paull and Rohrbach, 1985). CI symptom development can be divided into two events: the first relates to the exposure to temperature less than 10-12°C (Fig. 10.7), while the second is tissue darkening, which can range from brown to black (Paull and Rohrbach, 1985). After exposure of fruit to 10-12°C, tissue darkening (Fig. 10.7) is more pronounced between 17.5°C and 27.5°C (Paull

Fig. 10.7. Chilling-induced internal browning of pineapple stored at various temperatures for different length of storage and then removed to higher temperature, generally 20°C (data from Akamine, 1963; Smith, 1983; Paull and Rohrbach, 1985; Abdullah et al., 1986), and effect of different temperatures after removal from 14 days at 8°C on development of internal-browning severity (from Paull and Rohrbach, 1985).

Duration \

Severity.

and Rohrbach, 1985). The development of tissue darkening is also related to preharvest shading and low temperatures (Linford, 1932; Akamine et al., 1975; Keetch and Balldorf, 1979; Swete Kelly and Bagshaw, 1993), ascorbic acid content (Miller, 1951; Teisson and Martin-Prevel, 1979; Paull and Rohrbach, 1985; Abdullah et al., 1986), lower sugars and opaque fruit (Abdullah and Rohaya, 1983; Paull and Rohrbach, 1985), storage atmosphere (Paull and Rohrbach, 1982; Hassan et al., 1985) and clone (Wilson Wijeratram et al., 1993; Sanewski and Giles, 1997). The symptoms are seen occasionally in Hawaii's cool-season fruit (Akamine et al., 1975) and can be more severe on the northern side of a bed than on the southern side.

The occurrence of CI following exposure to temperatures between 12 and 21°C (Smith, 1983) is difficult to reconcile with published findings and may be related to preharvest stress (Swarts, 1991; Swete Kelly and Bragshaw, 1993) or a delay in symptom development at these temperatures. Partial to complete control of CI symptom development has been achieved by waxing, polyethylene bagging (Paull and Rohrbach, 1982, 1985; Rohrbach and Paull, 1982; Abdullah et al, 1985; Paull and Rohrbach, 1985), heat treatments (Akamine et al., 1975; Akamine, 1976), controlled atmospheres (Abdullah et al., 1985; Paull and Rohrbach, 1985) and ascorbic acid application (Sun, 1971). Selection of hybrids for higher flesh ascorbic acid concentration significantly reduces CI symptom development and presumably storage life.

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