Fruits can
be classified based on their physiology and ripening behaviour : climacteric
and non-climacteric.
Climacteric
fruits have high respiration rate during the fruit’s ripening. During ripening, the production of ethylene
increase dramatically.
In a
nutshell, climacteric fruits are able to ripen after harvested.
Non-climacteric
fruits do not undergo a rapid ripening phase.
They mature slowly whist attached to the parent plant, and their eating
quality cannot improve after harvest.
Non-climacteric fruits have relatively low respiration rates that
decline slowly after harvest. They
produce ethylene at low rates. Application
of ethylene has little effect other than the hastening of senescence changes.
In short,
non-climacteric fruits are not able to ripen after harvested.
Climacteric
|
Non-Climacteric
|
able to ripen after
harvest
|
NOT able to ripen
after harvest
|
increase respiration
rate, peaked, then decline at senesce
|
NO drastic
respiration rate, decline after harvest
|
lots of biosynthetic
activity
|
LESS biosynthetic
activity
|
lots of ATP consumed
|
LESS ATP consumed
|
sharp ethylene
production
|
NO sharp ethylene
production
|
exogenous ethylene
trigger endogenous ethylene production
|
exogenous ethylene
DOES NOT trigger endogenous ethylene production
|
Climacteric
is the final physiological process that marks the end of fruit maturation and
the beginning of fruit senescence. It is
also defined as a period in the ontogeny of certain fruits in which a series of
biochemical changes initiated by the autocatalytic production of ethylene
making the changes from growth to senescence involving increased respiration
leading to ripening.
Several
major changes take place during ripening of climacteric fruits :
1..
production of ethylene
2. rise
in respiration rate
3. colour
change
4. flesh
softening
5. formation
of volatiles & flavours
1.
Production of ethylene
Ethylene
is a natural plant growth regulator that is synthesized by all plants. It has many biological functions in growing
plants. In fruit, ethylene plays an
equally major role in ripening of climacteric
fruits. Ethylene initiates the ripening
of climacteric fruits, hastens their senescence and abscission.
Climacteric
fruits show increase of ethylene production as respiration rate peak. Ethylene is both a promoter and a product of
fruit ripening, and an accelerant of senescence in vegetables and cut
flowers. Ethylene exposure brings about
an autocatalytic production of ethylene, and thus accelerate ripening.
Ethylene
as a ripening trigger is used commercially with banana, avocado and kiwifruit. Conversely, if fruits are to be stored a long
time, then the ambient ethylene must be remove.
2. Rise in respiration rate
All
living organisms must conduct respiration.
Respiration breaks down glucose and produce ATPs. ATPs were used in conversion of starch to
sucrose, which contributes to the sweetness of the fruit.
In
climacteric fruits, respiration rate rises rapidly during ripening, then
decreases as the fruit senesces.
By
decreasing the rate of respiration, post-harvest storage life of climacteric
fruits can be prolonged. So, ethylene is
removed using a scrubber. CO2
content can also be increased, while O2 level, temperature and
pressure are decreased.
3. Colour
change
Colour
change by fruits involves chlorophyll loss and increase in production of
yellow, orange, red or purple pigments.
However,
non-climacteric fruits also exhibit change of colour.
4. Flesh
softening
Softening
of fruit as hemicellulose & middle lamella degraded. Degradation of polysaccharides results in
senescence and abscission of fruits, as well as development of volatiles and
flavours.
5.
Formation of volatiles & flavours
Different
cell compartments degrade into amino acids, esters, aldehydes, alcohols,
terpenoids, etc. to create attractive volatiles and flovours.
Polysaccharides
are reduce to monosaccharides which contribute to the sweetness flavour.
These
volatiles and flavour join with sugars and acids in creating unique flavour of
every fruit. Mango’s ocimene, myrcene
& dimethylstyrene ; muskmelon’s ethyl-2-methyl butyrate, 3-methyl butyl
acetate, ethyl butyrate, ethyl hexanoate, hexyl acetate, benzyl aceate ;
apple’s butyl ethanoate, 2-metnyl butyl ethanoate, hexyl ethanoate ;
strawberry’s furaneol.
|
Climacteric
|
Non-Climacteric
|
Actinidiaceae
|
Kiwifruit
|
|
Annonaceae
|
Soursop Sugarapple
|
|
Anarcardiaceae
|
Mango
|
|
Arecales
|
Dates
|
|
Bromeliaceae
|
|
Pineapple
|
Bombacaceae
|
Durian
|
|
Caricaceae
|
Papaya
|
|
Cucurbitaceae
|
Cantaloupes
|
Cucumber Pumpkin
Squash
Watermelon
|
Ebenaceae
|
Persimmon
|
|
Ericaceae
|
|
Blueberry
|
Lauraceae
|
Avocado
|
|
Lythraceae
|
|
Pomegranate
|
Moraceae
|
Breadfruit
Fig
Jackfruit
|
|
Musaceae
|
Banana
|
|
Myrtaceae
|
Guava
|
Jambu Air
|
Oleaceae
|
|
Olive
|
Oxaladaceae
|
|
Starfruit
|
Rhamnaceae
|
|
Jujube
|
Passifloraceae
|
Passionfruit
|
|
Rosaceae
|
Apple
Apricot Nectarines
Peach
Pear
Plum
|
Blackberry Cherry
Raspberry Strawberry
|
Rutaceae
|
|
Grapefruit
Lime
Pamelo
Orange
Tangerine
|
Sapindaceae
|
|
Lychee
Rambutan
|
Sapotaceae
|
Ciku
|
|
Solanaceae
|
Eggplant
Tomato
|
Peppers
|
Vitaceae
|
|
Grape
|
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