Climacteric vs Non-climacteric Fruits can be divided into two groups according
to the regulatory mechanisms underlying their ripening process. Climacteric
fruit, such as tomato, apple and melon are characterized by a
ripening-associated increase in respiration and in ethylene production, the
phytohormone ethylene being the major trigger and coordinator of the ripening
process. By contrast, nonclimacteric fruits, such as grape, orange and
pineapple, are characterized by the lack of ethylene-associated respiratory
peak and the signaling pathways that drive the ripening process remain
elusive.
The identification of regulatory or structural genes controlling fruit
development and ripening is a necessary step towards enlarging our
understanding of the fruit biology and hence opening new leads for improving
fruit quality traits. However, the regulatory mechanisms common to both
climacteric and non-climacteric fruit remain elusive. Their identification
would have major consequences, not only in fundamental research aiming at
deciphering the interplay between hormones and the main regulatory networks in
plants, but also in terms of opening new avenues for commercial
application.
New tools for cross-species comparison allow now gene discovery in tomato and
grape. In the recent period, systematic comparisons have been performed at the
transcriptome level between fruit belonging to the same genus, the same family
(Moore et al. 2002) but also between fruit from distantly related families like
tomato and grape (Solanaceae and Vitacea). These studies highlighted the
interest of such approaches for deciphering the metabolic pathways leading to
the accumulation of compounds (vitamin C, carotenoids, anthocyanins, organic
acids) with high nutritional or sensorial value in the fruit, and for
understanding the regulation of fruit-specific processes such as ripening.
Fruits such as
peaches, pears, plums, nectarines, avocados and kiwis should have an even
color. They may be feel hard when first purchased but will soften, may change
color and become juicy or soft in several days at room temperature. Tomatoes
ripen and develop color with warmth and not sunlight; refrigerate when ripe.
Also, citrus
fruits should feel heavy and not hollow. Thin-skinned citrus have more juice
than do thick-skinned citrus. Refrigeration will not harm these types of fruit.
The chemical
responsible for the ripening process is a hormone called ethylene. Apples are a
good example of a fruit that have the power of ethylene. Many have learned the
trick to include a ripe apple or banana in a bowl with some unripened fruit as
a means of causing the other fruits to ripen more quickly. Another simple
solution to hasten ripening is to place fruit in a brown paper bag (prick a few
small holes in the bag–include an apple or banana if desired) and seal. The
trapped gas causes ripening and the fruit should start to ripen within
approximately 8 hours. Fruits such as green bananas and hard tomatoes may be
shipped to remote places and then sprayed with ethylene to hasten the ripening
process before they reach the supermarket.
At normal room temperature most climacteric fruit ripens from one to four days.
Once ripe, fruit should be refrigerated if not eaten within a day or so. Don't
be surprised if fully ripened fruit rots quickly. If a fruit gets overripe,
remove the individual piece from the remainder of the fruit. Because ethylene
is very powerful, the remainder of your fresh fruit would soon spoil. Once
fruit starts to ripen, the chemical process of “respiration“ occurs (rapid use
of oxygen and production of carbon dioxide) and is quite efficient. Even
refrigeration may not be a complete deterrent for overripe fruit. In other
words, the end stage of ripening is eventual decay.
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