Lactic Acid
<p><b >Lactic acid</b>, also known as <b >milk acid</b>, is a <a href="http://en.wikipedia.org/wiki/Chemical_compound" title="Chemical compound" >chemical compound</a> that plays a role in various <a href="http://en.wikipedia.org/wiki/Biochemistry" title="Biochemistry" >biochemical</a> processes and was first isolated in 1780 by the Swedish chemist <a href="http://en.wikipedia.org/wiki/Carl_Wilhelm_Scheele" title="Carl Wilhelm Scheele" >Carl Wilhelm Scheele</a>. Lactic acid is a <a href="http://en.wikipedia.org/wiki/Carboxylic_acid" title="Carboxylic acid" >carboxylic acid</a> with the <a href="http://en.wikipedia.org/wiki/Chemical_formula" title="Chemical formula" >chemical formula</a> C<sub >3</sub>H<sub >6</sub>O<sub >3</sub>. It has a <a href="http://en.wikipedia.org/wiki/Hydroxyl" title="Hydroxyl" >hydroxyl</a> group adjacent to the <a href="http://en.wikipedia.org/wiki/Carboxyl" title="Carboxyl" class="mw-redirect" >carboxyl</a> group, making it an <a href="http://en.wikipedia.org/wiki/Alpha_hydroxy_acid" title="Alpha hydroxy acid" >alpha hydroxy acid</a> (AHA).</p>
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In industry, <a href="http://en.wikipedia.org/wiki/Lactic_acid_fermentation" title="Lactic acid fermentation" >lactic acid fermentation</a> is performed by <a href="http://en.wikipedia.org/wiki/Lactic_acid_bacteria" title="Lactic acid bacteria" >lactic acid bacteria</a>. These bacteria can also grow in the <a href="http://en.wikipedia.org/wiki/Mouth" title="Mouth" >mouth</a>; the <a href="http://en.wikipedia.org/wiki/Acid" title="Acid" >acid</a> they produce is responsible for the <a href="http://en.wikipedia.org/wiki/Tooth" title="Tooth" >tooth</a> decay known as <a href="http://en.wikipedia.org/wiki/Caries" title="Caries" >caries</a>.<sup id="cite_ref-2" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-2" >[3]</a></sup><sup id="cite_ref-3" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-3" >[4]</a></sup><sup id="cite_ref-4" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-4" >[5]</a></sup><sup id="cite_ref-5" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-5" >[6]</a></sup>
In <a href="http://en.wikipedia.org/wiki/Medicine" title="Medicine" >medicine</a>, lactate is one of the main components of <a href="http://en.wikipedia.org/wiki/Lactated_Ringer%27s_solution" title="Lactated Ringer's solution" >lactated Ringer's solution</a> and <a href="http://en.wikipedia.org/wiki/Hartmann%27s_solution" title="Hartmann's solution" >Hartmann's solution</a>. These <a href="http://en.wikipedia.org/wiki/Intravenous" title="Intravenous" class="mw-redirect" >intravenous</a> fluids consist of <a href="http://en.wikipedia.org/wiki/Sodium" title="Sodium" >sodium</a> and <a href="http://en.wikipedia.org/wiki/Potassium" title="Potassium" >potassium</a> <a href="http://en.wikipedia.org/wiki/Cation" title="Cation" class="mw-redirect" >cations</a> along with lactate and <a href="http://en.wikipedia.org/wiki/Chloride" title="Chloride" >chloride</a> <a href="http://en.wikipedia.org/wiki/Anion" title="Anion" class="mw-redirect" >anions</a> in solution with distilled <a href="http://en.wikipedia.org/wiki/Water" title="Water" >water</a>, generally in concentrations <a href="http://en.wikipedia.org/wiki/Isotonicity" title="Isotonicity" class="mw-redirect" >isotonic</a> with <a href="http://en.wikipedia.org/wiki/Human" title="Human" >human</a> <a href="http://en.wikipedia.org/wiki/Blood" title="Blood" >blood</a>. It is most commonly used for fluid<a href="http://en.wikipedia.org/wiki/Resuscitation" title="Resuscitation" class="mw-redirect" >resuscitation</a> after blood loss due to <a href="http://en.wikipedia.org/wiki/Physical_trauma" title="Physical trauma" class="mw-redirect" >trauma</a>, <a href="http://en.wikipedia.org/wiki/Surgery" title="Surgery" >surgery</a>, or <a href="http://en.wikipedia.org/wiki/Burn_(injury)" title="Burn (injury)" class="mw-redirect" >burn injury</a>.
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<h2 >Foods</h2>
<p >Lactic acid is found primarily in sour <a href="http://en.wikipedia.org/wiki/Milk" title="Milk" >milk</a> products, such as <a href="http://en.wikipedia.org/wiki/Koumiss" title="Koumiss" class="mw-redirect" >koumiss</a>, <a href="http://en.wikipedia.org/wiki/Strained_yoghurt" title="Strained yoghurt" >laban</a>, <a href="http://en.wikipedia.org/wiki/Yogurt" title="Yogurt" >yogurt</a>, <a href="http://en.wikipedia.org/wiki/Kefir" title="Kefir" >kefir</a>, and some <a href="http://en.wikipedia.org/wiki/Cottage_cheese" title="Cottage cheese" >cottage cheeses</a>. The <a href="http://en.wikipedia.org/wiki/Casein" title="Casein" >casein</a> in fermented milk is coagulated (curdled) by lactic acid. Lactic acid is also responsible for the sour flavor of <a href="http://en.wikipedia.org/wiki/Sourdough" title="Sourdough" >sourdough</a> breads. This acid is used in beer brewing to lower the wort pH in order to reduce some undesirable substances such as tannins without giving off-flavors such as citric acid and increase the body of the beer.<sup class="Template-Fact" >[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a></i>]</sup>Some brewers and breweries will use food grade lactic acid to lower the pH in finished beers.<sup class="Template-Fact" >[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a></i>]</sup></p>
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In winemaking, a bacterial process, natural or controlled, is often used to convert the naturally present <a href="http://en.wikipedia.org/wiki/Malic_acid" title="Malic acid" >malic acid</a> to lactic acid, to reduce the sharpness and for other flavor-related reasons. This <a href="http://en.wikipedia.org/wiki/Malolactic_fermentation" title="Malolactic fermentation" >malolactic fermentation</a> is undertaken by the family of <a href="http://en.wikipedia.org/wiki/Lactic_acid_bacteria" title="Lactic acid bacteria" >lactic acid bacteria</a>.</p>
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As a <a href="http://en.wikipedia.org/wiki/Food_additive" title="Food additive" >food additive</a> it is approved for use in the EU,<sup id="cite_ref-24" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-24" >[25]</a></sup> USA<sup id="cite_ref-25" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-25" >[26]</a></sup> and Australia and New Zealand;<sup id="cite_ref-26" class="reference" ><a href="http://en.wikipedia.org/wiki/Lactic_acid#cite_note-26" >[27]</a></sup> it is listed by its INS number 270 or as <a href="http://en.wikipedia.org/wiki/E_number" title="E number" >E number</a> E270.
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