Post Harvest Management of Horticultural Crops

Physical methods of judging maturity

Physical methods
1. Fruit retention strength

It is the force required to pull the fruit from the tree which indicates the maturity status of the fruit.
Eg. Immature fruit required more force to detach from mother plant compared to ripe fruits.


2. Acoustic/sound tests

The sound of a fruit as it is tapped sharply with a finger knuckle can change during maturation and ripening. This method of testing fruit is sometimes used by consumers when purchasing fruit.
Eg. - Water melon fruit may be tapped in the field to judge whether they are ready to be harvested, ripe fruit gives dull sound and also in jackfruit


3. Skin colour

This is the common method used in fruits to judge maturity, where, the skin colour changes as the fruit matures or ripens. Colour changes may vary from cultivars, seasons, site, light etc. In most of the fruits GREEN colour changes to LIGHT GREEN/YELLOW/ RED/ PURPLE /VIOLET during ripening after the optimum maturity. When it is still green it may be possible to develop the colour after harvest but not all the flavour characteristics. If the fruit is harvested just as the yellow colour begins to show in the shoulders / panicles of the fruits, fruit can eventually ripen to an acceptable flavour.





The assessment of harvest maturity by skin colour changes usually on the judgement of the harvester, but colour charts are used for some cultivars of apple, chilli, peach and tomato. The chlorophyll fluorescence spectrometer or colorimeter used to detect the loss of chlorophyll.


4. Shape

The shape referred to the design of the fruit. Shape of fruit can change during maturation.

• Eg. Banana - individual fingers become more rounded on maturity from angular shape(refer fig.).
• Mango - immature fruit shoulder shows slope away from the fruit stalk; on more mature fruit shoulders become more level with point of attachment (fullness of the checks adjacent to the pedicle) (refer fig.).
5. Size

The change in size of crop as it is growing are frequently used to determine when it should be harvested. Eg.

Litchi, green beans, okra and asparagus and potato related to size at maturity.
In banana width of individual fingers can be used for determining their harvest maturity.
In baby corn more immature and smaller cob are marked for maturity.


6. Aroma/ Orgnoleptic quality

Fruits synthesize volatile chemicals as they may give its characteristic odour and can be used to determine whether it is ripe or not with indication of fruit flies. This method has limited scope in commercial application.

Figure : Organoleptic quality of a fruit in relationship to its ripening stage

7. Fruit opening

When the fruit is fully mature on the tree it splits.
Eg. - It is common in fruit of spice tree nutmeg, ackee tree. In vegetable like chow chow distal end of the fruit opens and large single seed emerges and germinates.


8. Abscission

Abscission layer is formed in the pedicel as the natural development in the fruit advanced. However, fruit harvested at this maturity will have only short marketable life.
Eg.: In cantaloupe, watermelons, harvesting before abscission layer is fully developed results inferior
flavoured fruit compared with those left on the vine for the full period.


9. Specific gravity

It is the relative gravity/weight of solids or liquids compared to pure distilled water at 16.7oC (62oF).
Eg. Cherries, watermelon, potato, ber and mango (at 1.015 immature and at 1.02 ready for harvest)


10. Firmness/solidity

Here harvester slightly presses vegetables such as cabbage and lettuce with his
thumb and finger. Harvest maturity is assessed on the basis of how much the vegetable yield to this pressure. Normally the back of the hand is used for testing the firmness of lettuce in order to avoid damage. Fruit may change in texture during maturation and especially during ripening; excessive moisture loss may also affect the texture of crops.


The textural changes can be detected by following ways
Destructive firmness test methods

a. Penetrometer / Pressure testers: Here a representative sample of fruits may be taken from the orchard and tested in a device ( Magness Taylor or Effegi fruit presser tester) which will give a numerical value of texture; when that value reaches a pre determined critical level then the fruits in that orchard are harvested.

Eg. Firmness test in mango 1.75 -2 kg.



Fig. Objective firmness measurement using Penetrometer


b. Tenderometer: It is used in peas only. As pea matures in the pod it is sweet and tender. As maturation progress sugars are converted to starch which coincides with the peas becoming firmer. Therefore for processing sample peas are taken from the field and their texture is tested in a shear cell. The whole field of peas is harvested when a particular tenderometer value is reached.




Fig.Tenderometer to test the pea maturity by presser tester


c. Fingure squeeze/touch: Here peas/beans/okra etc. are squeezed between the fingers to determine their firmness. Only experience plays a role here whether to harvest or not.