Maturity, Ripening, and Quality Relationships 67
have published an extensive review regarding the effects of 1-MCP, and hence the
discussion here will be limited to raising points pertaining directly to postharvest
produce degradation. Apples have been the most studied of fruits and vegetables in
terms of response to 1-MCP. For example, in ‘Anna,’ a summer apple, 1-MCP
significantly reduces the fruit’s propensity to become mealy in texture (Pre-Aymard
et al., 2003). However, not all apple cultivars respond to the same degree to 1-MCP
treatment (Watkins et al., 2000). The level of benefit is also enhanced if the apples
are held in controlled atmosphere storage conditions as opposed to cold air storage
(Watkins et al., 2000). This second aspect of response is due to the fact that high
carbon dioxide acts synergistically with 1-MCP in controlling softening in apples
(Lu and Toivonen, 2003).
Unfortunately, not all fruit responds well to 1-MCP treatment. In preclimacteric
bananas 1-MCP delays ripening-associated changes, but treated fruits do not properly
degreen and their aroma volatile production is inhibited (Golding et al., 1998). Such
response renders 1-MCP technology unuseful for mature, unripe bananas (Harris et
al., 2000). More recently, it has been demonstrated that response to 1-MCP by
partially ripened bananas is extremely variable and hence the technology would not
be commercially useful for the partially ripened product (Pelayo et al., 2003).
Another aspect of 1-MCP response relates to the effect the treatment may have
on storage disorder development. If disorders are increased, then reduction of quality
decline may be overshadowed by an increased incidence of such a disorder. This is
the case with ‘Shamouti’ oranges which show greater susceptibility to chilling injury
after treatment with 1-MCP (Porat et al., 1999). In contrast, pineapple has a lower
incidence of chilling injury-related internal browning after treatment with 1-MCP
(Selvarajah et al., 2001). Thus, whether 1-MCP increases or decreases incidence of
storage disorders depends on the fruit or vegetable in question.
While vegetables are not climacteric and are not expected to show a direct
response to 1-MCP (Blankenship and Dole, 2003), there are situations, such as mixed
loading of produce into trailers and containers, where an ethylene-sensitive vegetable
such as broccoli is exposed to ethylene (Saltveit, 1999). Treatment of broccoli with
1-MCP will prevent the reduction of shelf life caused by subsequent exposure to
relatively low ethylene concentrations in surrounding air (Ku and Wills, 1999; Fan
and Mattheis, 2000). Therefore, 1-MCP treatment could be seen as an insurance
against potential exposure to ethylene in postharvest handling situations and the
resultant acceleration of quality decline in fruits and vegetables, whether or not they
have climacteric ripening patterns.
3.4 RESPIRATORY METABOLISM IN RELATION TO QUALITY
3.4.1 NONCLIMACTERIC FRUITS AND VEGETABLES
Nonclimacteric fruits and vegetables are those that do not undergo sharp rises in
ethylene and respiration during the ripening process. Generally, declines in quality
in such fruits and vegetables tend to be relatively gradual in nature, and hence it
can be difficult to discern changes in maturity. Quality changes such as texture are