The time necessary for crops to successfully complete reproduction is species- and environment-dependent. Lifecycles can be completed in a few weeks or take several years depending on the plant species.
Crop development is divided into phenophases that are affected primarily by light and temperature changes, interacting with phytohormones. Some species are influenced more by light and others by temperature.
Read Also: Major Genetic Differences between Tropical and Temperate Livestock Breeds
Maturity and Quality Indices of Crop Products for Harvesting
Maturity at harvest is the most important determinant of storage life and final fruit quality. Immature fruit are highly susceptible to shriveling and mechanical damage and are of inferior flavor quality when ripe. Overripe fruit are likely to become soft and mealy with insipid flavor soon after harvest.
Fruit picked either prematurely or too late are more susceptible to post-harvest physiological disorders than those picked at the proper stage of maturity.
With a few exceptions, all fruits attain optimal eating quality when allowed to ripen on the plant. Some fruits are, however, picked at a mature but unripe stage of development so as to allow them to withstand post-harvest handling conditions when shipped over long distances.
Maturity indices for such fruit are based on a compromise between those indices that would ensure the best eating quality and those that provide flexibility in marketing.
Fruit can be divided into two groups:
1.those that are incapable of continuing their ripening process once removed from the plant, and
- those that can be harvested at the mature stage and allowed to ripen off the plant. Group 1 includes cane berries, cherry, citrus fruits, grape, lychee, pineapple, pomegranate, and strawberry.
Group 2 includes apple, apricot, avocado, banana, cherimoya, guava, kiwifruit, mango, nectarine, papaya, passion fruit, pear, peach, persimmon, plum, quince, and sapodilla.
Fruit in Group 1 produce very small quantities of ethylene and do not respond to ethylene treatment except in terms of de-greening (removal of chlorophyll); these should be picked when fully ripe to ensure good flavor quality.
Fruit in Group 2 produce comparably larger quantities of ethylene, which is associated with their ripening, and undergo more rapid and uniform ripening upon exposure to ethylene.
Many vegetables, particularly leafy vegetables and immature fruit vegetables (such as cucumbers, sweet corn, green beans, peas, and okras), attain optimum eating quality prior to reaching full maturity.
Read Also: Crossbreeding as Tool for Tropical Livestock Improvement
Maturity Indices for Crop Harvest Decision
The maturity index of a fruit provides an indication of its stage of development or maturation. Maturity indices are based on characteristics known to change as the fruit matures. Maturity indices for harvest can be either subjective or objective.
1. Physical Maturity Indices Used in Crop Harvesting
i. Skin colour: This factor is commonly applied to fruits, as skin colour changes during ripening. Some fruits exhibit no perceptible colour change during maturation. Assessment depends on the judgment of the harvester, but colour charts are available for cultivars such as apples, tomatoes, peaches, and chilli peppers.
ii. Optical methods: Light transmission properties can be used to measure fruit maturity based on chlorophyll content, which decreases during maturation. A bright light is used followed by darkness, and a sensor detects emitted light proportional to chlorophyll content.
iii. Shape: The shape of fruit can change during maturation. For instance, bananas become more rounded and less angular as they develop. Mangoes also change shape; the shoulders of immature mangoes slope away from the stalk, while in mature ones, they become level or raised above the point of attachment.
iv. Size: Size changes during growth often indicate harvest time. Partially mature cobs of Zea mays saccharata are sold as sweet corn, while smaller immature cobs are sold as baby corn. In banana, caliper measurement of finger width is used to determine maturity.
v. Aroma: Many fruits produce volatile chemicals that create characteristic odour during ripening. These may only be detectable when the fruit is fully ripe and are of limited use commercially.
vi. Fruit opening: Some fruits, like ackee, develop toxic compounds during ripening. Ackee fruit naturally split open at full maturity, showing black seeds on yellow arils, indicating reduced toxicity. Only naturally opened fruit over 15 mm in lobe separation are considered safe if seeds and membranes are removed.
vii. Leaf changes: Leaf condition can indicate harvest time. For example, potatoes for storage should be harvested soon after leaves and stems have died. Early harvest leads to poor skin resistance and increased susceptibility to diseases.
viii. Abscission: Formation of an abscission layer in the pedicel is a natural maturity sign. In cantaloupe melons, harvesting before full abscission development results in inferior flavour.
ix. Firmness: Fruit texture changes during ripening, becoming softer. These changes can be judged by touch or measured using devices like penetrometers or texture analyzers. Common testers include the Magness-Taylor and UC Fruit Firmness testers. Instruments like the Instron Universal Testing Machine may also be used, with all settings specified when reporting values.
x. Juice content: Juice content increases as fruit matures. A sample is extracted and the juice volume is related to original mass to assess maturity.
2. Chemical Maturity Indices for Harvested Produce
i. Sugars: In climacteric fruits, starch accumulates during maturation and converts to sugar during ripening. In non-climacteric fruits, sugar accumulates during maturation. Sugars form the major part of the soluble solids in fruit juice. TSS (Total Soluble Solids) is measured using a refractometer.
ii. Starch: Starch levels in developing fruit like apple and pear indicate harvest maturity.
iii. Acidity: Acidity changes during maturation and ripening. In citrus and other fruits, acidity progressively decreases as the fruit matures.
Quality Indices of Fruits in Agricultural Markets
Quality, the degree of excellence or superiority of fresh fruits and their products, is a combination of attributes, properties, or characteristics that give each commodity value as food.
The relative importance of each quality component depends on the commodity and its intended use (e.g., fresh or processed) and varies among producers.
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