Ripening

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A bunch of Cabernet Sauvignon wine grapes at varying levels of ripeness Veraison Cabernet Sauvignon.jpg
A bunch of Cabernet Sauvignon wine grapes at varying levels of ripeness

Ripening is a process in fruits that causes them to become more palatable. In general, fruit becomes sweeter, less green, and softer as it ripens. Even though the acidity 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. [1] Climacteric fruits ripen after harvesting and so some fruits for market are picked green (e.g. bananas and tomatoes).

Contents

Underripe fruits are also fibrous, 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 palatability of fruit.

Science

1-Methylcyclopropene is used as a synthetic plant growth regulator. Methylcyclopropene.png
1 ‑ Methylcyclopropene is used as a synthetic plant growth regulator.

Developing fruits produce compounds like alkaloids and 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 is not eaten before the seeds are fully developed. [3]

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. [4] [5]

Agents

Lemons turn yellow as they ripen. 2017-10-26 Ripening lemons on a tree, Albufeira (2).JPG
Lemons turn yellow as they ripen.

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, bananas are picked when green and artificially ripened after shipment by being exposed to ethylene.

Calcium carbide is also used in some countries for artificially ripening fruit. When calcium carbide comes in contact with moisture, it produces 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. [6]

Climacteric fruits continue ripening after being picked, a process accelerated by ethylene 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 has not fully started to ripen.

Stages

Climacteric fruits 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. [7] 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. [8] Colour change is the result of pigments, which were always present in the fruit, becoming visible when chlorophyll is degraded. [9] However, additional pigments are also produced by the fruit as it ripens. [10]

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. [11] These enzymes include polygalacturonase. [9] This means that the fruit will become less firm as the structure of the fruit is degraded.

Ripening grape tomatoes in multiple stages Grape tomato cluster partially ripened.JPG
Ripening grape tomatoes in multiple stages

Enzymatic breakdown and hydrolysis of storage polysaccharides occurs during ripening. [9] The main storage polysaccharides include starch. [9] These are broken down into shorter, water-soluble molecules such as fructose, glucose and sucrose. [12] During fruit ripening, gluconeogenesis also increases. [9]

Acids are broken down in ripening fruits [12] 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. [13] This is mainly as a result of the general decrease in acid content that occurs when a fruit ripens. [9]

Tomatoes

Different fruits have different ripening stages. In tomatoes the ripening stages are:

Lists of climacteric and non-climacteric fruits

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

Honeycrisp apples Honeycrisp apples.jpg
Honeycrisp apples

Climacteric

Cultivated blackberries at various stages of ripeness: unripe (pale), ripening (red), and ripe (black) Kupine dozrijevaju na stabljici (Croatia).3.jpg
Cultivated blackberries at various stages of ripeness: unripe (pale), ripening (red), and ripe (black)

Non-climacteric

Regulation

There are two patterns of fruit ripening: climacteric that is induced by ethylene and non-climacteric that occurs independently of ethylene. [17] 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. [18] Ripening can be induced by abscisic acid, specifically the process of sucrose accumulation as well as color acquisition and firmness. [19] 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. [20] They suggested that this process involves ethylene receptors, a type of gasoreceptor, that may vary between climacteric and non-climacteric fruits. [21]

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. [17] 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. [17]

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. [19] 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. [19]

See also

Related Research Articles

<span class="mw-page-title-main">Polysaccharide</span> Long carbohydrate polymers such as starch, glycogen, cellulose, and chitin

Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using amylase enzymes as catalyst, which produces constituent sugars. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as cellulose and chitin.

<span class="mw-page-title-main">Accessory fruit</span> Botanical category of fruit

An accessory fruit is a fruit that contains tissue derived from plant parts other than the ovary. In other words, the flesh of the fruit develops not from the floral ovary, but from some adjacent tissue exterior to the carpel. As a general rule, the accessory fruit is a combination of several floral organs, including the ovary. In contrast, true fruit forms exclusively from the ovary of the flower.

<span class="mw-page-title-main">Plant hormone</span> Chemical compounds that regulate plant growth and development

Plant hormones are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, including embryogenesis, the regulation of organ size, pathogen defense, stress tolerance and reproductive development. Unlike in animals each plant cell is capable of producing hormones. Went and Thimann coined the term "phytohormone" and used it in the title of their 1937 book.

<span class="mw-page-title-main">Chromoplast</span> Pigment-bearing organelle in plant cells

Chromoplasts are plastids, heterogeneous organelles responsible for pigment synthesis and storage in specific photosynthetic eukaryotes. It is thought that like all other plastids including chloroplasts and leucoplasts they are descended from symbiotic prokaryotes.

<span class="mw-page-title-main">Jasmonate</span> Lipid-based plant hormones

Jasmonate (JA) and its derivatives are lipid-based plant hormones that regulate a wide range of processes in plants, ranging from growth and photosynthesis to reproductive development. In particular, JAs are critical for plant defense against herbivory and plant responses to poor environmental conditions and other kinds of abiotic and biotic challenges. Some JAs can also be released as volatile organic compounds (VOCs) to permit communication between plants in anticipation of mutual dangers.

<span class="mw-page-title-main">Methyl jasmonate</span> Chemical compound

Methyl jasmonate is a volatile organic compound used in plant defense and many diverse developmental pathways such as seed germination, root growth, flowering, fruit ripening, and senescence. Methyl jasmonate is derived from jasmonic acid and the reaction is catalyzed by S-adenosyl-L-methionine:jasmonic acid carboxyl methyltransferase.

<span class="mw-page-title-main">Strawberry</span> Edible fruit

The garden strawberry is a widely grown hybrid species of the genus Fragaria, collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely appreciated for its characteristic aroma, bright red color, juicy texture, and sweetness. It is consumed in large quantities, either fresh or in such prepared foods as jam, juice, pies, ice cream, milkshakes, and chocolates. Artificial strawberry flavorings and aromas are also widely used in products such as candy, soap, lip gloss, perfume, and many others.

<span class="mw-page-title-main">Systemin</span> Plant peptide hormone

Systemin is a plant peptide hormone involved in the wound response in the family Solanaceae. It was the first plant hormone that was proven to be a peptide having been isolated from tomato leaves in 1991 by a group led by Clarence A. Ryan. Since then, other peptides with similar functions have been identified in tomato and outside of the Solanaceae. Hydroxyproline-rich glycopeptides were found in tobacco in 2001 and AtPeps were found in Arabidopsis thaliana in 2006. Their precursors are found both in the cytoplasm and cell walls of plant cells, upon insect damage, the precursors are processed to produce one or more mature peptides. The receptor for systemin was first thought to be the same as the brassinolide receptor but this is now uncertain. The signal transduction processes that occur after the peptides bind are similar to the cytokine-mediated inflammatory immune response in animals. Early experiments showed that systemin travelled around the plant after insects had damaged the plant, activating systemic acquired resistance, now it is thought that it increases the production of jasmonic acid causing the same result. The main function of systemins is to coordinate defensive responses against insect herbivores but they also affect plant development. Systemin induces the production of protease inhibitors which protect against insect herbivores, other peptides activate defensins and modify root growth. They have also been shown to affect plants' responses to salt stress and UV radiation. AtPEPs have been shown to affect resistance against oomycetes and may allow A. thaliana to distinguish between different pathogens. In Nicotiana attenuata, some of the peptides have stopped being involved in defensive roles and instead affect flower morphology.

Polyphenol oxidase, an enzyme involved in fruit browning, is a tetramer that contains four atoms of copper per molecule.

<span class="mw-page-title-main">Chlorophyllase</span> Enzyme in chlorophyll metabolism

Chlorophyllase is an essential enzyme in chlorophyll metabolism. It is a membrane proteins commonly known as chlase (EC 3.1.1.14, CLH) with systematic name chlorophyll chlorophyllidohydrolase. It catalyzes the reaction

<span class="mw-page-title-main">1-Aminocyclopropane-1-carboxylate synthase</span> Class of enzymes

The enzyme aminocyclopropane-1-carboxylic acid synthase catalyzes the synthesis of 1-Aminocyclopropane-1-carboxylic acid (ACC), a precursor for ethylene, from S-Adenosyl methionine, an intermediate in the Yang cycle and activated methyl cycle and a useful molecule for methyl transfer:

<span class="mw-page-title-main">1-Methylcyclopropene</span> Synthetic plant growth regulator blocking the effects of ethylene (competitive inhibitor)

1-Methylcyclopropene (1-MCP) is a cyclopropene derivative used as a synthetic plant growth regulator. It is structurally related to the natural plant hormone ethylene and it is used commercially to slow down the ripening of fruit and to help maintain the freshness of cut flowers.

<span class="mw-page-title-main">Anthocyanin</span> Class of chemical compounds

Anthocyanins, also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compound that gives flowers a blue color, Anthokyan, in his treatise "Die Farben der Blüthen". Food plants rich in anthocyanins include the blueberry, raspberry, black rice, and black soybean, among many others that are red, blue, purple, or black. Some of the colors of autumn leaves are derived from anthocyanins.

Generally, fleshy fruits can be divided into two groups based on the presence or absence of a respiratory increase at the onset of ripening. This respiratory increase—which is preceded, or accompanied, by a rise in ethylene—is called a climacteric, and there are marked differences in the development of climacteric and non-climacteric fruits. Climacteric fruit can be either monocots or dicots and the ripening of these fruits can still be achieved even if the fruit has been harvested at the end of their growth period. Non-climacteric fruits ripen without ethylene and respiration bursts, the ripening process is slower, and for the most part they will not be able to ripen if the fruit is not attached to the parent plant. Examples of climacteric fruits include apples, bananas, melons, apricots, tomatoes, as well as most stone fruits. Non-climacteric fruits on the other hand include citrus fruits, grapes, and strawberries Essentially, a key difference between climacteric and non-climacteric fruits is that climacteric fruits continue to ripen following their harvest, whereas non-climacteric fruits do not. The accumulation of starch over the early stages of climacteric fruit development may be a key issue, as starch can be converted to sugars after harvest.

<span class="mw-page-title-main">Post-harvest losses (vegetables)</span> Losses in quantity and quality of produce before consumer purchase

Post-harvest losses of vegetables and fruit occur at all points in the value chain from production in the field to the food being placed on a plate for consumption. Post-harvest activities include harvesting, handling, storage, processing, packaging, transportation and marketing.

<span class="mw-page-title-main">Genetically modified tomato</span> Tomato with modified genes

A genetically modified tomato, or transgenic tomato, is a tomato that has had its genes modified, using genetic engineering. The first trial genetically modified food was a tomato engineered to have a longer shelf life, which was on the market briefly beginning on May 21, 1994. The first direct consumption tomato was approved in Japan in 2021. Primary work is focused on developing tomatoes with new traits like increased resistance to pests or environmental stresses. Other projects aim to enrich tomatoes with substances that may offer health benefits or be more nutritious. As well as aiming to produce novel crops, scientists produce genetically modified tomatoes to understand the function of genes naturally present in tomatoes.

<span class="mw-page-title-main">Blue tomato</span> Various tomato cultivars

Blue tomatoes, also called purple tomatoes, are tomatoes that have been bred to produce high levels of anthocyanins, a class of pigments responsible for the blue and purple colours of many fruits, including blueberries, blackberries and chokeberries. Anthocyanins may provide protection for the plant against insects, diseases, and ultraviolet radiation. Some of these tomatoes have been commercialized under the names "Indigo Rose" and "SunBlack".

<span class="mw-page-title-main">Polygalacturonase</span>

Endo-polygalacturonase (EC 3.2.1.15, pectin depolymerase, pectolase, pectin hydrolase, and poly-α-1,4-galacturonide glycanohydrolase; systematic name (1→4)-α-D-galacturonan glycanohydrolase (endo-cleaving)) is an enzyme that hydrolyzes the α-1,4 glycosidic bonds between galacturonic acid residues:

Gaseous signaling molecules are gaseous molecules that are either synthesized internally (endogenously) in the organism, tissue or cell or are received by the organism, tissue or cell from outside and that are used to transmit chemical signals which induce certain physiological or biochemical changes in the organism, tissue or cell. The term is applied to, for example, oxygen, carbon dioxide, sulfur dioxide, nitrous oxide, hydrogen cyanide, ammonia, methane, hydrogen, ethylene, etc.

<span class="mw-page-title-main">Ethylene (plant hormone)</span> Alkene gas naturally regulating the plant growth

Ethylene (CH
2=CH
2) is an unsaturated hydrocarbon gas (alkene) acting as a naturally occurring plant hormone. It is the simplest alkene gas and is the first gas known to act as hormone. It acts at trace levels throughout the life of the plant by stimulating or regulating the ripening of fruit, the opening of flowers, the abscission (or shedding) of leaves and, in aquatic and semi-aquatic species, promoting the 'escape' from submergence by means of rapid elongation of stems or leaves. This escape response is particularly important in rice farming. Commercial fruit-ripening rooms use "catalytic generators" to make ethylene gas from a liquid supply of ethanol. Typically, a gassing level of 500 to 2,000 ppm is used, for 24 to 48 hours. Care must be taken to control carbon dioxide levels in ripening rooms when gassing, as high temperature ripening (20 °C; 68 °F) has been seen to produce CO2 levels of 10% in 24 hours.

References

  1. ↑ Kimball, Dan (1991). "The Brix/Acid Ratio". Citrus Processing. pp. 55–65. doi:10.1007/978-94-011-3700-3_4. ISBN   978-94-010-5645-8.
  2. ↑ Blankenship, Sylvia M; Dole, John M (April 2003). "1-Methylcyclopropene: a review". Postharvest Biology and Technology. 28 (1): 1–25. doi:10.1016/S0925-5214(02)00246-6.
  3. ↑ Lunawat, Dev (2019-05-06). "Why do bananas go bad so fast?". Science ABC. Retrieved 2019-12-03.
  4. ↑ Shan, Wei; Kuang, Jian-fei; Wei, Wei; Fan, Zhong-qi; Deng, Wei; Li, Zheng-guo; Bouzayen, Mondher; Pirrello, Julien; Lu, Wang-jin; Chen, Jian-ye (October 2020). "MaXB3 Modulates MaNAC2, MaACS1, and MaACO1 Stability to Repress Ethylene Biosynthesis during Banana Fruit Ripening". Plant Physiology. 184 (2): 1153–1171. doi:10.1104/pp.20.00313. PMC   7536691 . PMID   32694134.
  5. ↑ Hartman, Sjon (October 2020). "MaXB3 Limits Ethylene Production and Ripening of Banana Fruits". Plant Physiology. 184 (2): 568–569. doi:10.1104/pp.20.01140. PMC   7536662 . PMID   33020325.
  6. ↑ "How to Ripen Fruit Faster". HuffPost. 26 December 2017.
  7. ↑ Shinozaki, Y.; et al. (2018). "High Resolution spatiotemporal transcriptome mapping of tomato fruit development and ripening". Nature Communications. 9 (1): 364. Bibcode:2018NatCo...9..364S. doi:10.1038/s41467-017-02782-9. PMC   5785480 . PMID   29371663.
  8. ↑ Van de Poel, Bram; et al. (2014). "Tissue specific analysis reveals a differential organization and regulation of both ethylene biosynthesis and E8 during climacteric ripening of tomato". BMC Plant Biology. 14: 11. doi: 10.1186/1471-2229-14-11 . PMC   3900696 . PMID   24401128.
  9. 1 2 3 4 5 6 Prasanna, V.; Prabha, T.N.; Tharanathan, R.N. (2007). "Fruit ripening phenomena-an overview". Critical Reviews in Food Science and Nutrition. 47 (1): 1–19. doi:10.1080/10408390600976841. PMID   17364693. S2CID   30271189.
  10. ↑ Atwell, Brian J.; Kriedemann, Paul E.; Turnbull, Colin G.N., eds. (1999). "11.5.5 Colour and flavour". Plants in Action: Adaptation in Nature, Performance in Cultivation. Macmillan Education Australia. ISBN   978-0732944391.
  11. ↑ Xuewu Duana; Guiping Chenga; En Yanga; Chun Yia; Neungnapa Ruenroengklina; Wangjin Lub; Yunbo Luoc; Yueming Jiang (November 2008). "Modification of pectin polysaccharides during ripening of postharvest banana fruit". Food Chemistry. 111 (1): 144–9. doi:10.1016/j.foodchem.2008.03.049.
  12. 1 2 Medlicott, A.P.; Thompson, A.K. (1985). "Analysis of sugars and organic acids in ripening mango fruits (Mangifera indica L. var Keitt) by high performance liquid chromatography". J. Sci. Food Agric. 36 (7): 561–6. doi:10.1002/jsfa.2740360707.
  13. ↑ Bashir, H.A.; Abu-Goukh, A.A. (2003). "Compositional changes during guava fruit ripening". Food Chemistry. 80 (4): 557–563. doi:10.1016/j.foodchem.2008.03.049.
  14. ↑ "Guide to ripening stages" (PDF). Lagorio family companies.
  15. ↑ Theologis, A. (1992). "One Rotten Apple Spoils the Whole Bushel: The Role of Ethylene in Fruit Ripening". Cell. 70 (2): 181–4. doi:10.1016/0092-8674(92)90093-R. PMID   1638627. S2CID   44506282.
  16. ↑ "All fruit and vegetables are not created equal when it comes to proper storage conditions".
  17. 1 2 3 Concha, Cristóbal M.; Figueroa, Nicolás E.; Poblete, Leticia A.; Oñate, Felipe A.; Schwab, Wilfried; Figueroa, Carlos R. (2013-09-01). "Methyl jasmonate treatment induces changes in fruit ripening by modifying the expression of several ripening genes in Fragaria chiloensis fruit". Plant Physiology and Biochemistry. 70: 433–444. doi:10.1016/j.plaphy.2013.06.008. hdl: 10533/131171 . ISSN   0981-9428. PMID   23835361.
  18. ↑ Aharoni, Asaph; Keizer, Leopold C. P.; Broeck, Hetty C. Van Den; Blanco-Portales, Rosario; Muñoz-Blanco, Juan; Bois, Gregory; Smit, Patrick; Vos, Ric C. H. De; O'Connell, Ann P. (2002-07-01). "Novel Insight into Vascular, Stress, and Auxin-Dependent and -Independent Gene Expression Programs in Strawberry, a Non-Climacteric Fruit". Plant Physiology. 129 (3): 1019–1031. doi:10.1104/pp.003558. ISSN   0032-0889. PMC   166497 . PMID   12114557.
  19. 1 2 3 Jiang, Yueming; Joyce, Daryl C. (2003-02-01). "ABA effects on ethylene production, PAL activity, anthocyanin and phenolic contents of strawberry fruit". Plant Growth Regulation. 39 (2): 171–174. doi:10.1023/A:1022539901044. ISSN   0167-6903. S2CID   4217356.
  20. ↑ Tian, M. S.; Prakash, S.; Elgar, H. J.; Young, H.; Burmeister, D. M.; Ross, G. S. (2000-09-01). "Responses of strawberry fruit to 1-Methylcyclopropene (1-MCP) and ethylene". Plant Growth Regulation. 32 (1): 83–90. doi:10.1023/A:1006409719333. ISSN   0167-6903. S2CID   36992887.
  21. ↑ Kieber, Joseph J.; Schaller, G. Eric (2019-07-01). "Behind the Screen: How a Simple Seedling Response Helped Unravel Ethylene Signaling in Plants". The Plant Cell. 31 (7): 1402–1403. doi:10.1105/tpc.19.00342. ISSN   1040-4651. PMC   6635871 . PMID   31068448.
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