Thursday, February 28, 2013

Climacteric Fruits


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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