Postharvest Management of Fruits and Vegetables: Maturity and Ripening Process

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What is the significance of the corky layer that forms at the stem end of a mature fruit?

The corky layer stops the inflow of food material from the plant, making the fruit dependent on its own reserves.

Describe the changes that occur in a fruit during the ripening process.

During ripening, carbohydrates are dehydrated, sugars accumulate, typical flavors develop, and characteristic colors emerge.

Why is it essential to harvest fruits at the correct stage of maturity?

Harvesting at the correct maturity stage facilitates proper ripening, allows for distant transportation, and maximizes storage life.

What problems can arise from harvesting immature fruits?

Immature fruits may develop white patches or air pockets during ripening, and lack the proper sugar-acid ratio, taste, and flavor. Signup and view all the answers

How does the ripening process relate to senescence in fruits?

Fruit ripening is a genetically programmed stage of development that overlaps with senescence. Signup and view all the answers

What are the consequences of harvesting over-mature or fully ripe fruits?

Over-mature or fully ripe fruits are easily susceptible to microbial and physiological spoilage, and have a considerably reduced storage life. Signup and view all the answers

What is the primary function of carotenoids in fruits?

Carotenoids give rise to a wide range of colors in fruits, from red to blue. Signup and view all the answers

What additional compounds are synthesized during fruit ripening, aside from carotenoids?

Additional compounds synthesized during fruit ripening are beta-carotene and lycopene. Signup and view all the answers

What class of compounds primarily contributes to the characteristic flavor of individual fruits and vegetables?

Volatile compounds, such as esters, alcohols, aldehydes, acids, and ketones, primarily contribute to the characteristic flavor of individual fruits and vegetables. Signup and view all the answers

Describe the general trend observed in the ascorbic acid (vitamin C) content of fruits during growth, maturity, and ripening.

The ascorbic acid content in fruits decreases during maturity and ripening, after initially increasing during growth. Signup and view all the answers

How does the phenolic content in fruits change during growth and maturation?

The phenolic content of most fruits declines from high levels during early growth to low levels when the fruit is physiologically mature and susceptible to ripening. Signup and view all the answers

What happens to the free amino acid levels in fruits during senescence (aging)?

During senescence, the level of free amino acids in fruits increases, reflecting a breakdown of enzymes and decreased metabolic activity. Signup and view all the answers

Explain the role of starch in fruit ripening and how it differs from vegetables like potatoes and peas.

During fruit ripening, accumulated starch is hydrolyzed into sugars like glucose and fructose, increasing sugar levels. In contrast, in vegetables like potatoes and peas, higher sucrose content at the immature stage converts into starch as they mature. Signup and view all the answers

What is the characteristic event associated with fruit ripening in terms of sugar accumulation?

The accumulated starch is hydrolyzed into sugars (glucose, fructose, or other sugars), which is known as a characteristic event for fruit ripening. Signup and view all the answers

Describe the trend in organic acid levels during fruit ripening and potential reasons for this change.

There is a downward trend in the levels of organic acids during fruit ripening. This decline could be due to increased membrane permeability allowing acid storage in respiring cells, formation of malic acid salts, reduced acid translocation from leaves, reduced ability to synthesize acids with maturity, translocation into sugars, or dilution effect from increased fruit volume. Signup and view all the answers

What are the primary pigment changes that occur during fruit maturation?

With the approach of maturation, the most obvious change is the degradation of chlorophyll, accompanied by the synthesis of other pigments, usually either anthocyanins or carotenoids. Signup and view all the answers

Compare and contrast the sugar accumulation mechanisms in fruits that ripen on the plant versus those that ripen off the plant.

In fruits that ripen on the plant, sugar levels tend to increase due to increased sugar importation from the plant. In fruits that ripen off the plant, sugar levels increase due to the mobilization of starch reserves within the fruit. Signup and view all the answers

Explain the potential role of membrane permeability in the observed changes in organic acid levels during fruit ripening.

The decline in organic acid content during fruit ripening might be the result of an increase in membrane permeability, which allows acids to be stored in the respiring cells, reducing their levels in the fruit. Signup and view all the answers

What is the defining characteristic of a ripe fruit according to the text?

A ripe fruit attains its full flavour, aroma, and other characteristics of the best fruit of that particular cultivar. Signup and view all the answers

Explain the difference between the terms 'mature' and 'ripe' for climacteric and non-climacteric fruits.

For non-climacteric fruits, 'mature' and 'ripe' are essentially synonymous. However, for climacteric fruits, a mature fruit requires a period before attaining a desirable stage of edibility (ripeness). Signup and view all the answers

What are the major enzymes implicated in the softening of fruits during ripening?

The major enzymes implicated in the softening of fruits during ripening are pectin esterase, polygalacturonase, cellulase, and $\beta$-galactosidase. Signup and view all the answers

What are the main components of the cell wall, and what changes occur in the cell wall during fruit ripening?

The main components of the cell wall are pectic substances and cellulose, along with small amounts of hemicellulose and non-cellulosic polysaccharides. During ripening, the pectic polysaccharides in the middle lamella are degraded and solubilized, leading to a loss of neutral sugars and acidic pectin from the cell wall. Signup and view all the answers

Classify the following fruits as climacteric or non-climacteric: apple, cherry, citrus, pineapple.

Apple is climacteric, cherry and citrus are non-climacteric, and pineapple is non-climacteric. Signup and view all the answers

Explain the significance of the changes in the middle lamella during fruit ripening.

The changes in the middle lamella, which is rich in pectic polysaccharides, are significant because the degradation and solubilization of these pectic substances contribute to the softening of the fruit during ripening. Signup and view all the answers

What is the role of potassium permanganate (KMnO4) in extending the shelf life of fruits and vegetables?

Potassium permanganate (KMnO4) can absorb ethylene gas, which helps minimize ripening and increase shelf life when used at a concentration of 100 ppm soaked in filter paper. Signup and view all the answers

How does packaging in the absence of oxygen affect the shelf life of fruits and vegetables?

Packaging in the absence of oxygen, either under vacuum or with an oxygen scavenger, leads to an extension of shelf life in terms of color and odor stability due to low oxidation rates. Signup and view all the answers

What are some commonly used oxygen absorbents in fruit and vegetable packaging?

Mixtures of iron powder and sodium chloride, as well as activated carbon, are extensively used as oxygen absorbents in fruit and vegetable packaging. Signup and view all the answers

What is the role of sodium ortho-phenyl phenate (SOPP) in post-harvest handling of fruits and vegetables?

Sodium ortho-phenyl phenate (SOPP) is an antifungal agent that provides protection against molds and stem-end rot, particularly in the form of diphenyl wraps. Signup and view all the answers

Explain the use of inhibitors like MH (1000-2000 ppm) and 2-dimethyl-hydrazide (10,000 ppm) in post-harvest handling of crops like mango and apple.

MH (1000-2000 ppm) is used as a post-harvest treatment for mango, while 2-dimethyl-hydrazide (10,000 ppm) is used for apples. These inhibitors help extend the shelf life of these crops. Signup and view all the answers

How can auxins like 2,4-D and 2,4,5-T be used in post-harvest handling of fruits like grapes, figs, and mangoes?

Auxins like 2,4-D (5 ppm for grapes) and 2,4,5-T (25 ppm for figs, 100 ppm for mangoes) can be used to advance ripening and potentially increase shelf life when applied at specific concentrations and stages (pre-harvest for grapes and figs, post-harvest for mangoes). Signup and view all the answers