Maturity Indices of Important Fruits & Vegetables

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INTRODUCTION

The maturity of fruits and vegetables is an indication of the development of the crop and its progress for becoming a marketable product. Selection of right stage of maturity for harvest is an important aspect, which has considerable influence on storage life and quality and final acceptance by the consumer.

Maturity can be of two types – physiological maturity and commercial maturity. Physiological maturity refers to the point in the development of an organ (e.g. fruit, leaf) or organism (e.g. ornamental plant) when maximum growth has been achieved and the organ or organism has matured to the extent that the next development stage can be completed. In case of fruit, ripening can be considered as the next development stage, preceding the senescence stage. 
The commercial or horticultural maturity is the characteristic state of a plant organ required by the consumer. It is concerned with the timing of the harvest to meet particular market requirements. Commercial maturity bears little relation to physiological maturity, and may occur at any stage during development, maturation, ripening or senescence. Examples of commercial maturity include bean sprouts (during early stage of development), cucumber (during maturation) and tomato (during ripening). Chilli can be harvested (commercially mature) at ‘green stage’ of fruit for ‘green chilli’ market and at ‘red ripe’ stage for drying to be used as spice. At both these stages, chilli fruits are commercially or horticulturally mature. The term ‘immaturity’, ‘optimum maturity’ and ‘over maturity’ can be related to these market requirements. To a green chilli market, a red ripe chilli is ‘over mature’ and to the red ripe chilli market green chilli is ‘immature’.

Maturity Indices of Commercially Important Fruits:

1.  Mango:

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The various criteria recommended for judging maturity are red blush colour development on the shoulders, falling off of one or two ripe fruits from the plant naturally, the specific gravity of fruit ranging from 1.01 to 1.02 and in general fruits attain maturity 90-120 days from the fruit set stage. Sometimes maturity indices like change in pulp colour from white to pale yellow and slowing down of latex flow from the stalk of plucked fruits also serve the purpose.

2.  Banana:

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The fruits are usually harvested when the ridges on the surface of the skin change from angular to round i.e. after the attainment of the ¾ full stage. The maturity of fruits can also be adjudged by some other physical characters and chemical analysis. The physical characters like change in skin colour or development of blush or visually lighter colour is also taken into account to determine the maturity of fruits. In addition, fruits attain the size specific to variety on maturity. However, for long distance transport attainment of ¾ maturity is taken as harvesting index. 

3.  Citrus:

The fruits are generally harvested when the changes in rind colour take place. The colour break stage (change in colour from green to yellow) is taken as criterion for judging the maturity of lime and lemon. In citrus, total soluble solid (TSS): acid ratio is considered to be a good index for judging maturity, which varies from variety to variety. 

4.  Papaya:

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The fruits should be left on the tree until they mature fully. Usually the fruits are harvested when they are of full size, light green with a tinge of yellow at apical end. On ripening the latex becomes watery from milky. 

5.  Pineapple:

The fruits are usually harvested when the surface colour is between colour break and quarter yellow for shipment by sea and a half to three-quarter yellow colour for transportation by air. Harvesting for local market and distant market should be done at the full maturity stage and 75-80 per cent maturity stage, respectively. At maturity, the eyelets get flattened. 

6.  Grapes:

In grapes, the basal berries mature and ripen first and the harvesting of immature berries are never advisable as these do not ripen after harvest. The physical appearance like change in colour from dark green to light green, yellow or red or purple depending upon the type of cultivars, glossyness and softness of berries are also taken as indices for judging maturity. The estimation of TSS: acid ratio is also taken as criteria for judging the maturity. The TSS and acidity of berries are determined by refractometer and titration, respectively. 

7.  Sapota:

In sapota, various criteria have been suggested for judging the maturity e.g. development of a dull orange colour or potato colour, showing light yellow streak instead of a green streak when scratched and disappearance of browny scales on the fruit surface. 

8.  Guava:

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Guava fruits mature 4-5 months after flowering. At maturity the specific gravity varies from 0.95-0.96, while TSS and acid content ranges from 12-13° Brix and 0.36 to 0.41% respectively. 

9.  Jackfruit:

Several indices are commonly used to determine the optimum time to pick the fruits. A dull, hollow sound is produced when the fruit is tapped by the finger; the fruit spines become well developed and wide spaced; the spines yield to moderate pressure and lastly there is development of aroma. For distant market, fruit should be harvested when still firm and without any aroma.

10.  Pomegranate:

The fruits are ready for harvest in 5-6 months after flowering. The fruits are picked when the skin turn slightly yellow and the fruit gives a metallic sound when tapped. Likewise, the ripe fruits give a distinct cracking sound of grain cracking when pressed slightly on the slices. 

11.  Apple:

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Apple may be harvested when a fruit separates easily from the branch, retains firmness of pulp and taste which are desirable. On maturity the skin colour changes from green to yellow or red depending upon the cultivars. The days from complete flowering can also be taken as a criterion to assess the maturity, which varies from 90±4 days in early maturing varieties to 180±5 days in late maturing varieties.

12.  Pear:
Pear is harvested when firm and green for canning, while fully mature fruits are harvested for fresh consumption. Days from full flowering, TSS and firmness can also be used for judging the maturity. 

13.  Peach:

Various criteria have been advised for judging the maturity of peaches like fruit size, shape, firmness, starch content of fruits etc. Usually peaches are picked when they are still hard as they can ripen well in storage or in transit. 

14.  Plum:

Change of ground colour of fruits from green to yellow or red depending upon the varieties, firmness and TSS content of fruits and days from full flowering are used to assess the maturity of fruits. 

15.  Strawberry:

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Strawberries are generally harvested when half to three-fourth of skin develops colour. For distant shipment green or white and still hard berries are harvested.       

Maturity Indices of  Commercially Important Vegetables  :

1.  Broccoli:

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The best stage of harvesting is before the buds begin to open, the heads remain compact and the yellow petals have not come out. The total length of the stalk and the head can be 15 to 25 cm depending on the variety. The axillary shoots grow and form smaller heads sometime after harvest of the main head. These can also be harvested for marketing.

2.  Cauliflower:

Stage of maturity is determined by curd size and its compactness. If harvesting is delayed, the curds become loose and discoloured. If the produce is meant for storage, it is better to harvest when the curds are not fully exposed and still covered with central whorl of leaves. 

3.  Cabbage:

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Solidity and firmness of the heads are the usual maturity characteristics used. Colour of the head is used as an added index. The head turns a lighter shade of green when full development is attained. 

4.  Celery:

Generally, celery requires blanching, although some growers prefer to sell it green. There is no specific time of harvest for celery though some like to harvest it as early as possible to take advantage of higher price. Blanching of the petioles and stalks and slight enlargement of the heart and inner leaves are used as picking indices. 

5.  Carrot:

Depending on the variety, the attainment of desired size is the primary consideration. Marketing of roots begins as soon as they attain acceptable size even though they have not attained full size specific to the variety. The roots must be harvested before emergence of the seed stalk.   

6.  Eggplant:

Fruits should be picked as soon as they have attained the desired size, before they harden or show streaks of unusual colour. The skin should be bright and glossy and seeds undeveloped.

7.  Tomato:

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Harvesting depend upon the purpose for which it is grown and time to be taken for reaching the destination. Six maturity stages are recognized. These are mature green, breaker, turning, pink, light red and red. In ‘breaker’ stage only up to 10% of the fruit surface especially at the blossom end is pink or red and in ‘red’ stage more than 90% of the fruit surface is red. In India fruits, for a distant market, are harvested at ‘breaker’ stage and they ripen during transit. For nearby market and for processing, it is better to harvest at a latter stage. The colour of the fruit can be measured by a colour chart or a colour measuring instrument using light transmittance technique. 

8.  Potato:

Setting of skin, starch content and leaf senescence are harvest indices. To catch early market and to get high price, potatoes are also harvested before attaining full maturity. These tubers are not fit for storage and should be disposed of quickly. 

9.  Garlic & Onion:

Onions are harvested depending upon the purpose for which the crop is grown. It requires 45 to 90 days from field setting for green onions and 90 to 150 days for bulb depending upon the variety. Onions should be harvested one week after 50% crop shows neck fall. Garlic is ready for harvesting when the tops turn yellowish or brownish and show signs of drying up and bend over. 

10.  Okra:

Fruits are harvested when they are tender and exhibiting maximum growth rate. At this stage, the blossom end of the fruits, when bent, breaks easily. It takes 7 to 8 days to become ready for harvesting after fruit set. Frequent picking promotes fruit development and increases yield. 

11.  Pea:

Quality of pea depends on sugar content and tenderness. With increasing maturity and size, sugar declines rapidly with an increase in starch and protein. Thus a high sugar content is an indication of high quality. The appearance of the pod is an added indication of maturity. Since firmness increases with maturity, a tenderometer is used to measure tenderness. Calculation of degree days is also done for mechanical harvesting. 

12.  Radish:

The crop matures in 3 to 4 weeks in case of quick growing varieties and in 8 to 10 weeks in case of the Chinese varieties. The crop is harvested when the roots are still tender before they become pithy and fibrous.  

References:  

1. Kader, A.A. (ed.) (1992) Post-harvest Technology of Horticultural Crops (2nd edition), University of California, Berkley.
 2. Thompson, A.K. (2003) Fruits and Vegetables: Harvesting Handling and Storage, Blackwell Publishing, UK.
 3. Watada, A.E., Herner, R.C., Kader, A., Romani, R.J. and Staby, G.L. (1984) Terminology for the description of Developmental stages of horticultural Corpp. Hort. Science, 19: 20-21.
 4. Wills, R., McGlasson, B., Graham, D. and Joyce, D. (2004) Post-harvest (4th edition), CAB International, U.K.