Editing Olive (section)

===Table olives===
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Table olives are classified by the [[International Olive Council]] (IOC) into three groups according to the degree of ripeness achieved before harvesting:<ref name="nyt">{{cite news |author1=Julia Moskin |title=Olives, Flavored by Time, Seasoned With Memories |url=https://www.nytimes.com/2007/10/17/dining/17oliv.html |access-date=28 January 2020 |work=The New York Times |date=17 October 2007 |archive-date=28 January 2020 |archive-url=https://web.archive.org/web/20200128172728/https://www.nytimes.com/2007/10/17/dining/17oliv.html |url-status=live }}</ref>
# '''Green olives''' are picked when they have obtained full size, while unripe; they are usually shades of green to yellow and contain the bitter [[phytochemical]] [[oleuropein]].<ref name="nyt" />
# '''Semi-ripe or turning-colour olives''' are picked at the beginning of the ripening cycle, when the colour has begun to change from green to multicolour shades of red to brown. Only the skin is coloured, as the flesh of the fruit lacks pigmentation at this stage, unlike that of ripe olives.
# '''Black olives''' or '''ripe olives''' are picked at full maturity when fully ripe, displaying colours of purple, brown or black.<ref name="nyt" /> To [[leaching (chemistry)|leach]] the oleuropein from olives, commercial producers use [[lye]], which neutralizes the bitterness of oleuropein, producing a mild flavour and soft texture characteristic of California black olives sold in cans.<ref name="nyt" /> Such olives are typically preserved in [[brine]] and [[Sterilization (microbiology)#Foods|sterilized under high heat]] during the [[canning]] process.<ref name="ioc">{{cite web |title=Olives darkened by oxidation |url=https://www.internationaloliveoil.org/glossary/5875-olives-darkened-by-oxidation/ |publisher=International Olive Council |access-date=28 January 2020 |date=4 December 2019 |archive-date=28 January 2020 |archive-url=https://web.archive.org/web/20200128172730/https://www.internationaloliveoil.org/glossary/5875-olives-darkened-by-oxidation/ |url-status=live }}</ref>

==== Fermentation and curing ====
[[File:GraberOliveHouseVatRoom.JPG|thumb|Vat room used for curing at [[Graber Olive House]]]]

Raw or fresh olives are naturally very bitter; to make them palatable, olives must be cured and [[Fermentation in food processing|fermented]], thereby removing [[oleuropein]], a bitter phenolic compound that can reach levels of 14% of dry matter in young olives.<ref name="Omar-2010">{{cite journal|pmid=21179340|pmc=3002804|year=2010|last1=Omar|first1=S.H.|title=Oleuropein in olive and its pharmacological effects|journal=Scientia Pharmaceutica|volume=78|issue=2|pages=133–154|doi=10.3797/scipharm.0912-18}}
</ref> In addition to oleuropein, other phenolic compounds render freshly picked olives unpalatable and must also be removed or lowered in quantity through curing and fermentation. Generally speaking, phenolics reach their peak in young fruit and are converted as the fruit matures.<ref name="epikouria2006" /> Once ripening occurs, the levels of phenolics sharply decline through their conversion to other organic products, which render some cultivars edible immediately.<ref name="Omar-2010" /> One example of an edible olive native to the island of [[Thasos]] is the ''throubes'' black olive, which becomes edible when allowed to ripen in the sun, shrivel, and fall from the tree.<ref>{{cite web|url=http://www.olivessa.co.za/throubes/|title=Throubes|publisher=Olives South Africa|access-date=2017-03-22|archive-date=2013-11-27|archive-url=https://web.archive.org/web/20131127094519/http://www.olivessa.co.za/throubes/|url-status=dead}}</ref><ref>{{cite magazine |title=Eat Like a Man |url=http://www.esquire.com/blogs/food-for-men/martini-olive-alternative-090810 |magazine=Esquire|access-date=22 September 2011|date=2010-09-08 }}</ref>

The curing process may take from a few days with lye, to a few months with brine or salt packing.<ref name="yada">{{cite web |first1=Sylvia |last1=Yada |first2=Linda |last2=Harris |url=https://anrcatalog.ucanr.edu/pdf/8267.pdf |title=Olives: Safe Methods for Home Pickling |publisher=University of California, Division of Agricultural and Natural Resources |access-date=December 6, 2014 |archive-date=October 9, 2015 |archive-url=https://web.archive.org/web/20151009235904/https://anrcatalog.ucanr.edu/pdf/8267.pdf |url-status=live }}</ref> With the exception of California style and salt-cured olives, all methods of curing involve a major fermentation involving bacteria and yeast that is of equal importance to the final table olive product.<ref name="Kailis, Stanley G. 2007">Kailis, Stanley G. & Harris, David John  (2007). ''Producing table olives''. Landlinks Press.</ref> Traditional cures, using the natural microflora on the fruit to induce fermentation, lead to two important outcomes: the leaching out and breakdown of oleuropein and other unpalatable phenolic compounds, and the generation of favourable metabolites from bacteria and yeast, such as organic acids, probiotics, glycerol, and esters, which affect the sensory properties of the final table olives.<ref name="Omar-2010" /> Mixed bacterial/yeast olive fermentations may have probiotic qualities.<ref>{{cite journal|doi=10.1016/j.foodres.2012.10.004|url=https://www.researchgate.net/publication/233986307|title=Screening of lactic acid bacteria isolated from fermented table olives with probiotic potential|journal=Food Research International|volume=50|pages=135–142|year=2013|last1=Bautista-Gallego|first1=J.|last2=Arroyo-López|first2=F.N.|last3=Rantsiou|first3=K.|last4=Jiménez-Díaz|first4=R.|last5=Garrido-Fernández|first5=A.|last6=Cocolin|first6=L.|hdl=2318/121637|s2cid=59404600 |hdl-access=free}}</ref><ref>{{cite journal|doi=10.1016/j.lwt.2011.01.029|title=Characterization of yeasts from Portuguese brined olives, with a focus on their potentially probiotic behavior|journal=LWT – Food Science and Technology|volume=44|issue=6|pages=1349|year=2011|last1=Silva|first1=T.|last2=Reto|first2=M.|last3=Sol|first3=M.|last4=Peito|first4=A.|last5=Peres|first5=C.M.|last6=Peres|first6=C.|last7=Malcata|first7=F. Xavier}}</ref> [[Lactic acid]] is the most important metabolite, as it lowers the pH, acting as a natural preservative against the growth of unwanted pathogenic species. The result is table olives which can be stored without refrigeration. Fermentations dominated by lactic acid bacteria are, therefore, the most suitable method of curing olives. Yeast-dominated fermentations produce a different suite of metabolites which provide poorer preservation, so they are corrected with an acid such as citric acid in the final processing stage to provide microbial stability.<ref name="Fernández, A. Garrido 1997" />

The many types of preparations for table olives depend on local tastes and traditions. The most important commercial examples are listed below.

'''Lebanese or Phoenician fermentation:''' Applied to green, semiripe, or ripe olives. Olives are soaked in salt water for 24–48 hours. Then they are slightly crushed with a rock to hasten the fermentation process. The olives are stored for a period of up to a year in a container with salt water, lemon juice, lemon peels, laurel and olive leaves, and rosemary. Some recipes may contain white vinegar or olive oil.{{citation needed|date=June 2023}}

'''Spanish or Sevillian fermentation:''' Most commonly applied to green olive preparation, around 60% of all the world's table olives are produced with this method.<ref>{{cite journal|pmid=22783248|pmc=3390769|year=2012|last1=Botta|first1=C|title=Microbial dynamics and biodiversity in table olive fermentation: Culture-dependent and -independent approaches|journal=Frontiers in Microbiology|volume=3|pages=245|last2=Cocolin|first2=L|doi=10.3389/fmicb.2012.00245|doi-access=free}}</ref> Olives are soaked in lye (dilute NaOH, 2–4%) for 8–10 hours to hydrolyse the oleuropein. They are usually considered "treated" when the lye has penetrated two-thirds of the way into the fruit. They are then washed once or several times in water to remove the caustic solution and transferred to fermenting vessels full of brine at typical concentrations of 8–12% NaCl.<ref>University of Catania PhD in Food Science and Technology, Food Microbiology: "Isolation and characterization of yeasts isolated from naturally fermented olives with brine bioprotective function"  Laboratory of Food Microbiology, DISPA, Agrarian Faculty.</ref> The brine is changed on a regular basis to help remove the phenolic compounds. {{citation needed|date=June 2023}}

Fermentation is carried out by the natural microbiota present on the olives that survive the lye treatment process. Many organisms are involved, usually reflecting the local conditions or [[terroir]] of the olives. During a typical fermentation [[Gram-negative bacteria|gram-negative]] [[Enterobacterales|enterobacteria]] flourish in small numbers at first but are rapidly outgrown by lactic acid bacteria species such as ''Leuconostoc mesenteroides'', ''Lactobacillus plantarum'', ''Lactobacillus brevis'' and ''Pediococcus damnosus''. These bacteria produce lactic acid to help lower the pH of the brine and therefore stabilize the product against unwanted pathogenic species. A diversity of yeasts then accumulate in sufficient numbers to help complete the fermentation alongside the lactic acid bacteria. Yeasts commonly mentioned include the teleomorphs ''[[Pichia anomala]]'', ''[[Pichia membranifaciens]]'', ''[[Debaryomyces hansenii]]'' and ''[[Kluyveromyces marxianus]]''.<ref name="Fernández, A. Garrido 1997" />

Once fermented, the olives are placed in fresh brine and acid corrected, to be ready for market.{{citation needed|date=June 2023}}

'''Sicilian or Greek fermentation:''' Applied to green, semiripe and ripe olives, they are almost identical to the Spanish type fermentation process, but the lye treatment process is skipped and the olives are placed directly in fermentation vessels full of brine (8–12% NaCl). The brine is changed on a regular basis to help remove the phenolic compounds. As the caustic treatment is avoided, lactic acid bacteria are only present in similar numbers to yeast and appear to be outdone by the abundant yeasts found on untreated olives. As very little acid is produced by the yeast fermentation, lactic, acetic, or citric acid is often added to the fermentation stage to stabilize the process.<ref name="Kailis, Stanley G. 2007" />

'''Picholine or directly brined fermentation:''' Applied to green, semi-ripe, or ripe olives, they are soaked in lye typically for longer periods than Spanish style (e.g. 10–72 hours) until the solution has penetrated three-quarters of the way into the fruit. They are then washed and immediately brined and acid corrected with citric acid to achieve microbial stability. Fermentation still occurs carried out by acidogenic yeast and bacteria but is more subdued than other methods. The brine is changed on a regular basis to help remove the phenolic compounds, and a series of progressively stronger concentrations of salt are added until the product is fully stabilized and ready to be eaten.<ref name="Fernández, A. Garrido 1997" />

'''Water-cured fermentation:''' Applied to green, semi-ripe, or ripe olives, these are soaked in water or weak brine and this solution is changed on a daily basis for 10–14 days. The oleuropein is naturally dissolved and leached into the water and removed during a continual soak-wash cycle. Fermentation takes place during the water treatment stage and involves a mixed yeast/bacteria ecosystem. Sometimes, the olives are lightly cracked with a blunt instrument to trigger fermentation and speed up the fermentation process. Once debittered, the olives are brined to concentrations of 8–12% NaCl and acid corrected and are then ready to eat.<ref name="Kailis, Stanley G. 2007" />

'''Salt-cured fermentation:''' Applied only to ripe olives, since it is only a light fermentation. They are usually produced in Morocco, Turkey, and other eastern Mediterranean countries. Once picked, the olives are vigorously washed and packed in alternating layers with salt. The high concentration of salt draws the moisture out of olives, dehydrating and shriveling them until they look somewhat analogous to a raisin. Once packed in salt, fermentation is minimal and only initiated by the most halophilic yeast species such as ''Debaryomyces hansenii''. Once cured, they are sold in their natural state without any additives.<ref name="Fernández, A. Garrido 1997" /> So-called '''oil-cured olives''' are cured in salt and then soaked in oil.<ref>{{cite web|title=Oil-Cured Olives: A Kalamata Substitute?|url=https://www.cooksillustrated.com/how_tos/9998-oil-cured-olives-a-kalamata-substitute|publisher=Cooks Illustrated|date=May 2016|access-date=27 November 2016|archive-date=7 April 2016|archive-url=https://web.archive.org/web/20160407015508/https://www.cooksillustrated.com/how_tos/9998-oil-cured-olives-a-kalamata-substitute|url-status=live}}</ref>

'''California or artificial ripening:''' Applied to green and semi-ripe olives, they are placed in lye and soaked. Upon their removal, they are washed in water injected with compressed air, without fermentation. This process is repeated several times until both oxygen and lye have soaked through to the pit. The repeated, saturated exposure to air oxidises the skin and flesh of the fruit, turning it black in an artificial process that mimics natural ripening. Once fully oxidised or "blackened", they are brined and acid corrected and are then ready for eating.<ref name="nyt" /><ref name="ioc" />