Editing Malolactic fermentation (section)

{{Short description|Process in winemaking}}
[[File:Malolactic spotting.JPG|right|thumb|A winemaker running a [[paper chromatography]] test to determine whether a wine has completed malolactic fermentation]]

'''Malolactic conversion''' (also known as '''malolactic fermentation''' or '''MLF''') is a process in [[winemaking]] in which [[Tart (flavor)|tart]]-tasting [[malic acid]], naturally present in [[grape must]], is converted to softer-tasting [[lactic acid]]. Malolactic fermentation is most often performed as a [[secondary fermentation (wine)|secondary fermentation]] shortly after the end of the primary [[fermentation (wine)|fermentation]], but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white [[grape varieties]] such as [[Chardonnay]], where it can impart a "buttery" flavor from [[diacetyl]], a byproduct of the reaction.<ref>Tom Mansell ''"[http://palatepreess.com/2009/11/wine/buttery-bacteria-malolactic-fermentation-and-you/ Buttery bacteria: Malolactic fermentation and you] {{webarchive|url=https://web.archive.org/web/20160406144621/http://palatepreess.com/2009/11/wine/buttery-bacteria-malolactic-fermentation-and-you/ |date=2016-04-06 }}"'' Palate Press. 10 November 2009</ref>

The fermentation reaction is undertaken by the family of [[lactic acid bacteria]] (LAB); ''[[Oenococcus oeni]]'', and various species of ''[[Lactobacillus]]'' and ''[[Pediococcus]]''. Chemically, malolactic fermentation is a [[decarboxylation]], which means [[carbon dioxide]] is liberated in the process.<ref name="Wine Micro">K. Fugelsang, C. Edwards ''Wine Microbiology'' Second Edition pgs 29-44, 88-91, 130-135, 168-179 Springer Science and Business Media, New York (2010) {{ISBN|0387333495}}</ref><ref name="Jacobson">Jean Jacobson ''"Introduction to Wine Laboratory Practices and Procedures"'' pgs 188-191, Springer Science and Business Media, New York (2010) {{ISBN|978-1-4419-3732-2}}</ref>

The primary function of all these bacteria is to convert L-malic acid, one of the two major grape [[acids found in wine]], to another type of acid, L+ lactic acid. This can occur naturally. However, in commercial winemaking, malolactic conversion typically is initiated by an [[inoculation]] of desirable bacteria, usually ''O. oeni''. This prevents undesirable bacterial strains from producing "off" flavors. Conversely, commercial winemakers actively prevent malolactic conversion when it is not desired, such as with fruity and floral white grape varieties such as [[Riesling]] and [[Gewürztraminer]], to maintain a more tart or acidic profile in the finished wine.<ref name="Yair">Dr. Yair Margalit, ''Winery Technology & Operations A Handbook for Small Wineries'' pgs 75-78, 103 & 183-184 The Wine Appreciation Guild (1996) {{ISBN|0-932664-66-0}}</ref><ref name="Zoecklein">B. Zoecklein, K. Fugelsang, B. Gump, F. Nury ''Wine Analysis and Production'' pgs 160-165, 292-302 & 434-447 Kluwer Academic Publishers, New York (1999) {{ISBN|0834217015}}</ref>

Malolactic fermentation tends to create a rounder, fuller [[mouthfeel]]. Malic acid is typically associated with the taste of green [[apple]]s, while lactic acid is richer and more buttery tasting. Grapes produced in cool regions tend to be high in acidity, much of which comes from the contribution of malic acid. Malolactic fermentation generally enhances the [[body (wine)|body]] and [[flavor (wine)|flavor]] persistence of [[wine]], producing wines of greater palate softness. Many winemakers also feel that better integration of fruit and [[oak character]] can be achieved if malolactic fermentation occurs during the time the wine is in barrel.<ref name="Oxford">J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pgs 422 & 508 Oxford University Press 2006 {{ISBN|0-19-860990-6}}</ref>

A wine undergoing malolactic conversion will be cloudy because of the presence of bacteria, and may have the smell of [[butter]]ed [[popcorn]], the result of the production of diacetyl. The onset of malolactic fermentation in the bottle is usually considered a [[wine fault]], as the wine will appear to the consumer to still be fermenting (as a result of CO<sub>2</sub> being produced).<ref name="Wine Faults">John Hudelson ''"Wine Faults-Causes, Effects, Cures"'' pgs 46-53, The Wine Appreciation Guild (2011) {{ISBN|9781934259634}}</ref> However, for early [[Vinho Verde]] production, this slight [[effervesce]] was considered a distinguishing trait, though [[Portuguese wine]] producers had to market the wine in [[Opacity (optics)|opaque]] bottles because of the increase in [[turbidity]] and sediment that the "in-bottle MLF" produced. Today, most Vinho Verde producers no longer follow this practice and instead complete malolactic fermentation prior to bottling with the slight sparkle being added by artificial [[carbonation]].<ref name="Boulton">R. Boulton, V. Singleton, L. Bisson, R. Kunkee ''Principles and Practices of Winemaking'' pgs 244-273 & 369-374 Springer 1996 New York {{ISBN|978-1-4419-5190-8}}</ref>