ABSTRACT
CONTENTS 13.1 Introduction ...................................................................................................................... 287 13.2 Apricot............................................................................................................................... 289
13.2.1 Physiological Disorders...................................................................................... 289 13.2.2 Disease Development ......................................................................................... 290 13.2.3 Fruit Biochemistry and Quality Attributes ..................................................... 291 13.2.4 Effects of MAP..................................................................................................... 292 13.2.5 Commercial Use .................................................................................................. 292
13.3 Cherries ............................................................................................................................. 292 13.3.1 Physiological Disorders...................................................................................... 292 13.3.2 Disease Development ......................................................................................... 294 13.3.3 Fruit Biochemistry and Quality Attributes ..................................................... 294 13.3.4 Effects of MAP..................................................................................................... 295 13.3.5 Commercial Use .................................................................................................. 296
13.4 Nectarine and Peach........................................................................................................ 296 13.4.1 Physiological Disorders...................................................................................... 296 13.4.2 Disease Development ......................................................................................... 301 13.4.3 Fruit Biochemistry and Quality Attributes ..................................................... 302 13.4.4 Effects of MAP..................................................................................................... 304 13.4.5 Commercial Use of CA and MAP.................................................................... 305
13.5 Plums ................................................................................................................................. 305 13.5.1 Physiological Disorders...................................................................................... 305 13.5.2 Disease Development ......................................................................................... 308 13.5.3 Fruit Biochemistry and Quality Attributes ..................................................... 309 13.5.4 Effects of MAP..................................................................................................... 309 13.5.5 Commercial Use .................................................................................................. 310
References.................................................................................................................................... 310
Peaches are characteristically soft fleshed and highly perishable fruit, with a limited postharvest life potential. Botanically, stone fruits are drupes. A drupe is a fleshy fruit with thin, edible outer skin (epicarp), an edible flesh of varying thickness beneath the skin (mesocarp) and a hard inner ovary wall that is highly lignified (endocarp), and is commonly referred as a stone or pit, which encloses a seed. In general, stone fruits contain
87% water with give 43 calories per 100 g fruit. The solid content of stone fruits consists of carbohydrates, organic acids, pigments, phenolics, vitamins, volatiles, antioxidants, and trace amounts of proteins and lipids that make them very attractive to consumers (Kader and Mitchell, 1989; USDA, 2003). Apricot, cherry, nectarine, peach, and plum commercial postharvest losses are mainly due to decay and internal breakdown (IB) or chilling injury (CI) (Ceponis et al., 1987; Mitchell and Kader, 1989). Apricot, nectarine, peach, and plum are climacteric fruits that display a rapid increase in ethylene production and an equally rapid rate of ripening. Contrary to the types of stone fruits, cherry is a nonclimacteric fruit, which implies that cherry ripening occurs during the last weeks before harvesting. As much as 25% of final weight is added in the last week of growth before harvesting accompanied with changes in color flavor and texture (Looney et al., 1996). From the commercial point of view, cherries are ready to eat at harvest time and then deteriorate very fast. The climacteric stone fruits are picked in a preclimacteric state (mature-firm) in order
to be marketed successfully. In some cases, this fruit does not acquire upon ripening the sensory characteristics needed to satisfy consumers. Ripening can be delayed by rapid removal of field heat and storage near to 08C. Peach, nectarine, and plum deteriorate quickly at ambient temperature, therefore, low temperature during storage is used to slow softening, flavor losses, and decay development. However, low-temperature disorders, CI classified as IB, limit the storage life of these fruit types under refrigeration. The onset of CI symptoms determines the postharvest storage=shipping potential because their development reduces consumer acceptance. CI is genetically influenced and triggered by a combination of storage temperature and storage period. It manifests itself as fruit that are dry and have a mealy or woolly texture (mealiness or woolliness), or hard textured fruit with no juice (leatheriness), fruit with flesh or pit cavity browning (internal browning), or with flesh bleeding (internal reddening) and development of off-flavor. This phenomenon (CI or IB) is triggered by storage temperature. It manifests itself as dry, mealy, woolly, or hard-textured fruit (not juicy), flesh or pit cavity browning, and flesh translucency usually radiating through the flesh from the pit. An intense red color development of the flesh (bleeding) usually radiating from the pit may be associated with this problem in some peach cultivars. Recently released cultivars rich in skin red pigment showed flesh bleeding that did not affect fruit taste. The development of this symptom has been associated with fruit maturity rather than storage temperature. In many cultivars, flavor is lost before visual CI symptoms are evident (Crisosto and Labavitch, 2002). There is large variability in CI susceptibility among peach cultivars (Mitchell and Kader, 1989; Crisosto et al., 1999c). In general, most of the mid-season and late-season peach cultivars are more susceptible to CI than early season cultivars (Mitchell and Kader, 1989), although as new cultivars are being released from a new genetic pool, the susceptibility to CI is becoming random in the new cultivar population (Crisosto et al., 1999a; Crisosto, 2002). It has been widely reported that the expression of CI symptoms develops faster and more intensely when susceptible fruit are stored at temperatures between about 2.28C and 7.68C (killing temperature zone) than those stored at 08C or below but above their freezing point (Harding and Haller, 1934; Smith, 1934; Mitchell and Kader, 1989). Therefore, market life is dramatically reduced when fruit are exposed to the killing temperature zone (Crisosto et al., 1999a). Increasing CO2 and decreasing O2 in the atmosphere around the fruit tissue has pro-
found effects on cellular metabolism and storage potential. These controlled atmosphere (CA) conditions reduce the respiration rate of fruits and vegetables (Kader, 1986). However, low oxygen may cause external symptoms such as skin browning and even black pitting on the skin. The internal damage is associated near the skin and surrounding the stone. In both cases, well-defined grayish brown or brown areas are formed. These areas
are not associated with mealy tissues and can occur anytime during cold storage (Kader, 1986). Ke et al. (1994) proposed that elevated CO2 influences respiration rates by regulating carbon flux through the tricarboxylic acid (TCA) cycle. High CO2 appears to increase carbon flux and maintain energy levels in the cell and enhance the alternative electron pathway by inducing and=or activating alternative oxidase and inhibiting cytochrome oxidase activity (Watkins, 2000). CA can also affect the activity of the enzymes involved in ethylene synthesis such as 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (Poneleit and Dilley, 1993). Therefore, ethylene is inhibited during storage in CA, but will recover following removal to air. CA also affects the cell wall-degrading enzymes that are responsible for fruit disassembly and whose imbalance or inhibition are associated with mealiness development. At the end of CA storage, the activities of pectin esterase and polygalacturonase were lower than following regular air storage at 08C (Zhou et al., 2000). However, both the activity and mRNA abundance of both enzymes increased after storage ripening to a greater extent in fruit that had been stored in CA than in fruit stored in air. This recovery of enzyme activity enabled pectin molecules to be cleaved quickly during ripening and led to normal fruit softening and development of juiciness. CA or modified atmosphere packaging (MAP) and relative humidity management
are used as supplements to proper fruit cold storage to limit water loss, delay ripening, and suppress diseases (Smith et al., 1987; Beaudry, 1999). Numerous researchers have contributed to identification of optimum CA to extend postharvest life of various commodities. Nowadays, produce amenable for long storage, such as apples, can be stored under CA regime up to 12 months. However, quality fruit flavor does not always persist after such prolonged storage. Studies have shown that after certain periods under CA, apples can still present an acceptable appearance but lack their characteristic taste (Brackmann et al., 1993). MAP is a practical way to modify the gas environment surrounding the fruit, and
utilizes polymeric films with different permeabilities to oxygen and carbon dioxide to prolong the shelf life of fruits and vegetables. Atmospheric modification evolves within the package as a result of the respiration rate of the fruit, temperature, and the gas diffusion characteristics of the film. Obviously, film selection is important to the system of MAP, since a proper matching of the commodity respiration with the film results in the passive evolution of an appropriate atmosphere within the sealed package (Zanderighi, 2001). The beneficial effects of the MAP technique for keeping quality and extending shelf life of fruits and vegetables are well known (Kader et al., 1989). However, MAP performance is sensitive to temperature and under improper management it can create off-flavor and decay problems, which negate the potential benefit of reducing weight loss. It has been reported that high CO2 and=or low O2 levels may accelerate the production of off-flavor (Kader et al., 1989; Golias and Bottcher, 2003).
