ripening
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Ripening is a process in
fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

fruit
s that causes them to become more
palatablePalatability is the Reward system, hedonic reward (i.e., pleasure) provided by foods or fluids that are agreeable to the "palate", which often varies relative to the homeostatic satisfaction of nutritional, Fluid balance, water, or Food energy, energ ...
. In general, fruit becomes
sweeter
sweeter
, less green, and softer as it ripens. Even though the
acidity An acid is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms ...
of fruit increases as it ripens, the higher acidity level does not make the fruit seem tarter. This effect is attributed to the Brix-Acid Ratio. Climacteric fruits ripen after harvesting and so some fruits for market are picked green (e.g.
bananas A banana is an elongated, edible fruit In botany, a fruit is the seed-bearing structure in flowering plants (also known as angiosperms) formed from the ovary after flowering. Fruits are the means by which angiosperms dissemin ...

bananas
and
tomatoes The tomato is the edible berry A berry is a small, pulpy, and often edible fruit In botany, a fruit is the seed-bearing structure in flowering plants (also known as angiosperms) formed from the ovary after flowering. Fruits are ...

tomatoes
). Underripe fruits are also
fibrous Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including ...
, not as juicy, and have tougher outer flesh than ripe fruits (see Mouth feel). Eating unripe fruit can lead to stomachache or stomach cramps, and ripeness affects the
palatabilityPalatability is the Reward system, hedonic reward (i.e., pleasure) provided by foods or fluids that are agreeable to the "palate", which often varies relative to the homeostatic satisfaction of nutritional, Fluid balance, water, or Food energy, energ ...
of fruit.


Science

11-Methylcyclopropene, Methylcyclopropene
1</a>1-Methylcyclopropene, Methylcyclopropene
is used as a synthetic plant growth regulator., 127x127px, leftDeveloping fruits produce compounds like Alkaloid, alkaloids and Tannin, tannins. These compounds are antifeedants, meaning that they discourage animals who would eat them while they are still ripening. This mechanism is used to make sure that fruit isn't eaten before the seeds are fully developed. At the molecular level, a variety of different plant hormones and proteins are used to create a negative feedback cycle which keeps the production of ethylene in balance as the fruit develops.


Agents

Ripening agents accelerate ripening. An important ripening agent is ethylene, a gaseous hormone produced by many plants. Many synthetic analogues of ethylene are available. They allow many fruits to be picked prior to full ripening, which is useful since ripened fruits do not ship well. For example,
banana A banana is an elongated, edible fruit – botanically a berry (botany), berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa (genus), Musa''. In some countries, Cooking banana, bananas used for c ...

banana
s are picked when green and artificially ripened after shipment by being exposed to
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...
.
Calcium carbide Calcium carbide, also known as calcium acetylide, is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical e ...

Calcium carbide
is also used in some countries for artificially ripening fruit. When calcium carbide comes in contact with moisture, it produces
acetylene Acetylene (systematic nameA systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is ...

acetylene
gas, which is similar in its effects to the natural ripening agent, ethylene. Acetylene accelerates the ripening process. Catalytic generators are used to produce ethylene gas simply and safely. Ethylene sensors can be used to precisely control the amount of gas. Covered fruit ripening bowls or bags are commercially available. These containers increase the amount of ethylene and carbon dioxide gases around the fruit, which promotes ripening.
Climacteric fruits The climacteric is a stage of fruit ripening associated with increased Ethylene#Ethylene as a plant hormone, ethylene production and a rise in cellular respiration. Apples, bananas, melons, apricots, and tomatoes, among others, are climacteric fru ...
continue ripening after being picked, a process accelerated by
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...
gas. Non-climacteric fruits can ripen only on the plant and thus have a short shelf life if harvested when they are ripe.


Indicators

Iodine (I) can be used to determine whether fruits are ripening or rotting by showing whether the starch in the fruit has turned into sugar. For example, a drop of iodine on a slightly rotten part (not the skin) of an apple will stay yellow or orange, since starch is no longer present. If the iodine is applied and takes 2–3 seconds to turn dark blue or black, then the process of ripening has begun but is not yet complete. If the iodine becomes black immediately, then most of the starch is still present at high concentrations in the sample, and hence the fruit hasn't fully started to ripen.


Stages

Climacteric fruits The climacteric is a stage of fruit ripening associated with increased Ethylene#Ethylene as a plant hormone, ethylene production and a rise in cellular respiration. Apples, bananas, melons, apricots, and tomatoes, among others, are climacteric fru ...
undergo a number of changes during fruit ripening. The major changes include fruit softening, sweetening, decreased bitterness, and colour change. These changes begin in an inner part of the fruit, the locule, which is the gel-like tissue surrounding the seeds. Ripening-related changes initiate in this region once seeds are viable enough for the process to continue, at which point ripening-related changes occur in the next successive tissue of the fruit called the pericarp. As this ripening process occurs, working its way from the inside towards outer most tissue of the fruit, the observable changes of softening tissue, and changes in color and carotenoid content occur. Specifically, this process activates ethylene production and the expression of ethylene-response genes affiliated with the phenotypic changes seen during ripening. Colour change is the result of pigments, which were always present in the fruit, becoming visible when chlorophyll is degraded. However, additional pigments are also produced by the fruit as it ripens. In fruit, the cell walls are mainly composed of polysaccharides including pectin. During ripening, a lot of the pectin is converted from a water-insoluble form to a soluble one by certain degrading enzymes. These enzymes include polygalacturonase. This means that the fruit will become less firm as the structure of the fruit is degraded.Enzymatic breakdown and hydrolysis of storage polysaccharides occurs during ripening. The main storage polysaccharides include starch. These are broken down into shorter, water-soluble molecules such as fructose, glucose and sucrose. During fruit ripening, gluconeogenesis also increases. Acids are broken down in ripening fruits and this contributes to the sweeter rather than sharp tastes associated with unripe fruits. In some fruits such as guava, there is a steady decrease in vitamin C as the fruit ripens. This is mainly as a result of the general decrease in acid content that occurs when a fruit ripens.


Tomatoes

Different fruits have different ripening stages. In tomatoes the ripening stages are: * Green: When the surface of the tomato is completely green * Breaker: When less than 11% of the surface is red * Turning: When less than 31% of the surface is red (but not less than 11%) * Pink: When less than 61% of the surface is red (but not less than 31%) * Light Red: When less than 91% of the surface is red (but not less than 61%) * Red: When the surface is nearly completely red.


Lists of climacteric and non-climacteric fruits

This is an incomplete list of fruits that ripen after picking (''Climacteric (botany), climacteric'') and those that do not (''non-climacteric'').


Climacteric


Non-climacteric


Regulation

There are two patterns of fruit ripening: climacteric that is induced by ethylene and non-climacteric that occurs independently of ethylene. This distinction can be useful in determining the ripening processes of various fruits, since climacteric fruits continue ripening after they are removed due to the presence of ethylene, while nonclimacteric fruits only ripen while still attached to the plant. In non-climacteric fruits, auxins act to inhibit ripening. They do this by repressing genes involved in cell modification and anthocyanin synthesis. Ripening can be induced by abscisic acid, specifically the process of sucrose accumulation as well as color acquisition and firmness. While ethylene plays a major role in the ripening of climacteric plants, it still has effects in non-climacteric species as well. In strawberries, it was shown to stimulate color and softening processes. Studies found that the addition of exogenous ethylene induces secondary ripening processes in strawberries, stimulating respiration. They suggested that this process involves ethylene receptors that may vary between climacteric and non-climacteric fruits.


Methyl jasmonate

Jasmonate is involved in multiple aspects of the ripening process in non-climacteric fruits. This class of hormones includes jasmonic acid and methyl jasmonate. Studies showed that the expression of genes involved in various pathways in ripening was increased with the addition of methyl jasmonate. This study found that methyl jasmonate led to an increase in red coloration and the accumulation of lignin and anthocyanins, which can be used as ripening indicators. The genes they analyzed include those involved in anthocyanin accumulation, cell wall modification, and ethylene synthesis; all of which promote fruit ripening.


Abscisic acid

ABA also plays an important role in the ripening of non-climacteric plants. It has been shown to increase the rate of ethylene production and anthocyanin concentrations. Ripening was enhanced, as seen with the accelerated fruit coloration and softening. This occurs because ABA acts as a regulator of ethylene production, increasing synthesis similarly to climacteric fruits.


See also

* Bletting, a post-ripening reaction that some fruits undergo before they are edible


References


External links

* * * * {{Authority control Fruit Horticulture