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class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Form of nitrogen available to wine yeast to use during fermentation</div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Red_wine_fermenting_just_after_pigeage.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/49/Red_wine_fermenting_just_after_pigeage.jpg/220px-Red_wine_fermenting_just_after_pigeage.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/49/Red_wine_fermenting_just_after_pigeage.jpg/330px-Red_wine_fermenting_just_after_pigeage.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/49/Red_wine_fermenting_just_after_pigeage.jpg/440px-Red_wine_fermenting_just_after_pigeage.jpg 2x" data-file-width="1280" data-file-height="960" /></a><figcaption>Yeast need a reliable source of nitrogen in forms that they can assimilate in order to successfully complete fermentation.</figcaption></figure> <p><b>Yeast assimilable nitrogen</b> or <b>YAN</b> is the combination of <a href="/wiki/Free_amino_nitrogen" title="Free amino nitrogen">free amino nitrogen</a> (FAN), <a href="/wiki/Ammonia" title="Ammonia">ammonia</a> (NH<sub>3</sub>) and <a href="/wiki/Ammonium" title="Ammonium">ammonium</a> (NH<sub>4</sub><sup>+</sup>) that is available for a yeast, e.g. the <a href="/wiki/Wine_yeast" class="mw-redirect" title="Wine yeast">wine yeast</a> <i><a href="/wiki/Saccharomyces_cerevisiae" title="Saccharomyces cerevisiae">Saccharomyces cerevisiae</a></i>, to use during <a href="/wiki/Fermentation_(wine)" class="mw-redirect" title="Fermentation (wine)">fermentation</a>. Outside of the <a href="/wiki/Fermentable_sugars_(wine)" class="mw-redirect" title="Fermentable sugars (wine)">fermentable sugars</a> <a href="/wiki/Glucose" title="Glucose">glucose</a> and <a href="/wiki/Fructose" title="Fructose">fructose</a>, <a href="/wiki/Nitrogen" title="Nitrogen">nitrogen</a> is the most important nutrient needed to carry out a successful fermentation that doesn't end prior to the intended point of <a href="/wiki/Dryness_(wine)" class="mw-redirect" title="Dryness (wine)">dryness</a> or sees the development of off-odors and related <a href="/wiki/Wine_faults" class="mw-redirect" title="Wine faults">wine faults</a>. To this extent winemakers will often supplement the available YAN resources with nitrogen additives such as <a href="/wiki/Diammonium_phosphate" title="Diammonium phosphate">diammonium phosphate</a> (DAP).<sup id="cite_ref-Zoecklein_1-0" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>However, the addition of excessive amounts of nitrogen can also create a hazard as other organisms besides beneficial wine yeast can utilize the nutrients. These include spoilage organisms such as <i><a href="/wiki/Brettanomyces" title="Brettanomyces">Brettanomyces</a></i>, <i><a href="/wiki/Acetobacter" title="Acetobacter">Acetobacter</a></i> and <a href="/wiki/Lactic_acid_bacteria" title="Lactic acid bacteria">Lactic acid bacteria</a> from the <i><a href="/wiki/Lactobacillus" title="Lactobacillus">Lactobacillus</a></i> and <i><a href="/wiki/Pediococcus" title="Pediococcus">Pediococcus</a></i> <a href="/wiki/Genera" class="mw-redirect" title="Genera">genera</a>. This is why many wineries will measure the YAN after <a href="/wiki/Harvest_(wine)" title="Harvest (wine)">harvest</a> and <a href="/wiki/Crushing_(wine)" class="mw-redirect" title="Crushing (wine)">crushing</a> using one of several methods available today including the nitrogen by <a href="/wiki/O-phthaldialdehyde" class="mw-redirect" title="O-phthaldialdehyde">o-phthaldialdehyde</a> assay (NOPA) which requires the use of a <a href="/wiki/Spectrometer" title="Spectrometer">spectrometer</a> or the <a href="/wiki/Formol_titration" class="mw-redirect" title="Formol titration">Formol titration</a> method. Knowing the YAN in the must allows winemakers to calculate the right amount of additive needed to get through fermentation, leaving only "nutrient desert" for any spoilage organisms that come afterwards.<sup id="cite_ref-Wine_Micro_2-0" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>The amount of YAN that winemakers will see in their grape <a href="/wiki/Must" title="Must">musts</a> depends on a number of components including <a href="/wiki/Grape_variety" class="mw-redirect" title="Grape variety">grape variety</a>, <a href="/wiki/Rootstock" title="Rootstock">rootstock</a>, <a href="/wiki/Vineyard_soils" class="mw-redirect" title="Vineyard soils">vineyard soils</a> and <a href="/wiki/Viticultural" class="mw-redirect" title="Viticultural">viticultural</a> practices (such as the use of <a href="/wiki/Fertilizers" class="mw-redirect" title="Fertilizers">fertilizers</a> and <a href="/wiki/Canopy_management" class="mw-redirect" title="Canopy management">canopy management</a>) as well as the climate conditions of particular <a href="/wiki/Vintage" title="Vintage">vintages</a>.<sup id="cite_ref-Jackson_3-0" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Components">Components</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=1" title="Edit section: Components"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Viognier_pomace_after_pressing.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/Viognier_pomace_after_pressing.JPG/220px-Viognier_pomace_after_pressing.JPG" decoding="async" width="220" height="164" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/Viognier_pomace_after_pressing.JPG/330px-Viognier_pomace_after_pressing.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/12/Viognier_pomace_after_pressing.JPG/440px-Viognier_pomace_after_pressing.JPG 2x" data-file-width="2592" data-file-height="1936" /></a><figcaption>Most of a grape's YAN content is found in the skins and seeds which gets left behind as pomace after pressing.</figcaption></figure> <p>YAN is a measurement of the primary organic (free amino acids) and inorganic (ammonia and ammonium) sources of nitrogen that can be assimilated by <i>S. cerevisiae</i>. There are several nitrogenous compounds found in must and wine including <a href="/wiki/Peptide" title="Peptide">peptides</a>, larger <a href="/wiki/Protein" title="Protein">proteins</a>, <a href="/wiki/Amide" title="Amide">amides</a>, <a href="/wiki/Biogenic_amines" class="mw-redirect" title="Biogenic amines">biogenic amines</a>, <a href="/wiki/Pyridine" title="Pyridine">pyridines</a>, <a href="/wiki/Purine" title="Purine">purines</a> and <a href="/wiki/Nucleic_acid" title="Nucleic acid">nucleic acids</a> but these cannot be directly used by yeast for metabolism. Taken together, the total nitrogen content of grape must can range from 60 to 2400 mg of nitrogen per liter, however not all of this nitrogen will be assimilable.<sup id="cite_ref-Zoecklein_1-1" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The lack of <a href="/wiki/Protease" title="Protease">protease</a> enzymes, which break down larger peptides into smaller components, that can work outside the cell, limits the size of the molecules that yeast can use as a source for nitrogen.<sup id="cite_ref-Jackson_3-1" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Boulton_4-0" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>The amount of YAN that winemakers will see in their grape musts depends on a number of components including grape variety, rootstock, vineyard soils and viticultural practices (such as the use of fertilizers and canopy management) as well as the climate conditions of particular vintages. Infections by mold, such as <i><a href="/wiki/Botrytis_cinerea" title="Botrytis cinerea">Botrytis cinerea</a></i> (known as <a href="/wiki/Noble_rot" title="Noble rot">noble rot</a> when it is desired) can reduce the amino acid content of grape must by as much as 61%.<sup id="cite_ref-Zoecklein_1-2" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Some regions are noted for having low YAN such as <a href="/wiki/Washington_State_(wine)" class="mw-redirect" title="Washington State (wine)">Washington State</a> which during a typical vintage will have 90% of tested must below 400 mg N/L<sup id="cite_ref-Spayd_5-0" class="reference"><a href="#cite_note-Spayd-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> and nearly a quarter be below 150 mg N/L.<sup id="cite_ref-Wine_Micro_2-1" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>In the vineyard, nitrogen is taken up by the <a href="/wiki/Grapevine" class="mw-redirect" title="Grapevine">grapevine</a> as <a href="/wiki/Nitrate" title="Nitrate">nitrate</a> (NO<sub>3</sub><sup>−</sup>), ammonium or <a href="/wiki/Urea" title="Urea">urea</a> which gets <a href="/wiki/Organic_redox_reaction" title="Organic redox reaction">reduced</a> into ammonia. Through additional reactions the nitrogen is incorporated into <a href="/wiki/Glutamine" title="Glutamine">glutamine</a> and <a href="/wiki/Glutamate" class="mw-redirect" title="Glutamate">glutamate</a> and eventually used in the synthesis of other amino acids and nitrogenous compounds.<sup id="cite_ref-Zoecklein_1-3" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> After harvest, the majority (around 80%) of available nitrogenous compounds found in the grapes are concentrated in the skins and seeds. These compounds get released into the must during the process of <a href="/wiki/Crushing_(wine)" class="mw-redirect" title="Crushing (wine)">crushing</a> and during <a href="/wiki/Maceration_(wine)" title="Maceration (wine)">maceration</a>/skin contact.<sup id="cite_ref-Boulton_4-1" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Even after <a href="/wiki/Pressing_(wine)" title="Pressing (wine)">pressing</a> up to 80% of initial nitrogen content within each grape berry will be left behind in the <a href="/wiki/Pomace" title="Pomace">pomace</a>.<sup id="cite_ref-Jackson_3-2" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Amino_acids">Amino acids</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=2" title="Edit section: Amino acids"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Of the Free Amino Nitrogen (FAN) that make up YAN, the amino acids <a href="/wiki/Arginine" title="Arginine">arginine</a>, <a href="/wiki/Proline" title="Proline">proline</a> and glutamine are the most abundant followed by <a href="/wiki/Alanine" title="Alanine">alanine</a>, <a href="/wiki/Threonine" title="Threonine">threonine</a>, <a href="/wiki/Serine" title="Serine">serine</a> and <a href="/wiki/Aspartic_acid" title="Aspartic acid">aspartic acid</a> in much smaller concentrations<sup id="cite_ref-Zoecklein_1-4" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> though trace amounts of most known amino acids can be found in grape must.<sup id="cite_ref-Wine_Micro_2-2" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Proline is usually the most concentrated and can represent up to 30% of the total amount of amino acids.<sup id="cite_ref-Boulton_4-2" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The exact amount FAN will vary and can range 22 to 1242 mg of nitrogen/liter of YAN being derived from free amino acids.<sup id="cite_ref-Spayd_5-1" class="reference"><a href="#cite_note-Spayd-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Cell_membrane_detailed_diagram_en.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/da/Cell_membrane_detailed_diagram_en.svg/220px-Cell_membrane_detailed_diagram_en.svg.png" decoding="async" width="220" height="91" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/da/Cell_membrane_detailed_diagram_en.svg/330px-Cell_membrane_detailed_diagram_en.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/da/Cell_membrane_detailed_diagram_en.svg/440px-Cell_membrane_detailed_diagram_en.svg.png 2x" data-file-width="877" data-file-height="361" /></a><figcaption>Specialized transporter proteins <i>(far left)</i> within the plasma membrane of yeast cells bring amino acid residues and small peptides into the cell coupled with a hydrogen ion that later gets expelled by the cell.</figcaption></figure> <p>While arginine, glutamine and other amino acids are rapidly consumed often very early in fermentation, proline is not consumed by yeast at all during the normal, anaerobic conditions of fermentations. This is because one of the enzymes required for its use is an <a href="/wiki/Oxidase" title="Oxidase">oxidase</a> (requiring molecular oxygen) and the other is <a href="/wiki/Repressor" title="Repressor">repressed</a> by the presence of ammonium (another source of assimilable nitrogen needed by yeast) in the must. However, well aerated <a href="/wiki/Starter_culture" class="mw-redirect" title="Starter culture">starter cultures</a> that contain must which hasn't had any diammonium phosphate added it to it will usually see some utilization of proline before the anaerobic conditions of fermentation kick in.<sup id="cite_ref-Zoecklein_1-5" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> When winemakers measure FAN, they need to be aware if their assay is including proline since this will make their YAN measurement higher. <a href="/wiki/Chardonnay" title="Chardonnay">Chardonnay</a> and <a href="/wiki/Cabernet_Sauvignon" title="Cabernet Sauvignon">Cabernet Sauvignon</a> are two <i><a href="/wiki/Vitis_vinifera" title="Vitis vinifera">Vitis vinifera</a></i> varieties that are known to have very high proline levels while <a href="/wiki/Riesling" title="Riesling">Riesling</a> and <a href="/wiki/Sauvignon_blanc" title="Sauvignon blanc">Sauvignon blanc</a> usually have very low levels.<sup id="cite_ref-Boulton_4-3" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Yeast transport amino acids and small peptides (less than 5 <a href="/wiki/Amino_acid_residues" class="mw-redirect" title="Amino acid residues">amino acid residues</a>) into the cell via an <a href="/wiki/Active_transport" title="Active transport">active transport</a> process that utilizes specialized <a href="/wiki/Membrane_protein" title="Membrane protein">membrane proteins</a> and the difference in the <a href="/wiki/PH" title="PH">pH</a> gradient of the acidic wine solution (pH between 3-4) and the near neutral pH of <a href="/wiki/Cytoplasm" title="Cytoplasm">cytoplasm</a> inside the yeast cells. The proton <a href="/wiki/Symport" class="mw-redirect" title="Symport">symport</a> proteins in the membrane take in the amino acid coupled with a hydrogen ion that later gets expelled by the cell via <a href="/wiki/ATPase" title="ATPase">a hydrogen ion pump</a>. This is an energy dependent process that becomes more energetically unfavorable for the yeast cell as fermentation progressed and ethanol levels increase, creating "passive leakage" of excess hydrogen ions into the cell. The cell's hydrogen ion pumps have to work even harder to maintain its internal pH so it sends a signal to the symport proteins to stop bringing other ions. This is one of the reasons why late fermentation nitrogen additions have little to no effective as the transport mechanisms of the nitrogen into the cell are shut down.<sup id="cite_ref-Boulton_4-4" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Ammonia_compounds">Ammonia compounds</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=3" title="Edit section: Ammonia compounds"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:DAP_addition_before_and_after.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/DAP_addition_before_and_after.JPG/220px-DAP_addition_before_and_after.JPG" decoding="async" width="220" height="295" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/DAP_addition_before_and_after.JPG/330px-DAP_addition_before_and_after.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b9/DAP_addition_before_and_after.JPG/440px-DAP_addition_before_and_after.JPG 2x" data-file-width="1936" data-file-height="2592" /></a><figcaption>Two buckets of red wine must with the top bucket showing the bluish color change after diammonium phosphate (an ammonia base) is added to the wine.</figcaption></figure> <p>Throughout fermentation ammonium is the primary form of assimilable nitrogen available to yeast.<sup id="cite_ref-Zoecklein_1-6" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> However, at crushing the juice may contain anywhere from 0 to 150 mg/L of ammonium salts, depending on the how much nitrogen the grapevine received in the vineyard.<sup id="cite_ref-Boulton_4-5" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>In the cell, the inorganic ammonia and ammonium ions get "fixed" through a series of chemical reactions that ultimately yields the organic nitrogen source glutamate.<sup id="cite_ref-Wine_Micro_2-3" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The ammonium ion also serves as an <a href="/wiki/Allosteric_regulation" title="Allosteric regulation">allosteric regulator</a> for <a href="/wiki/Phosphofructokinase" title="Phosphofructokinase">one of the enzymes</a> used in <a href="/wiki/Glycolysis" title="Glycolysis">glycolysis</a> and may also have an effect on how the yeast cell transports glucose and fructose into the cell.<sup id="cite_ref-Boulton_4-6" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The proteins used in the main glucose transport system have been shown to have a <a href="/wiki/Half-life" title="Half-life">half-life</a> of 12 hours. In the studies that put yeast cells through "ammonia starvation" the entire system shut down after 50 hours which gives strong evidence that a lack of ammonia/ammonium can create increase risk of having a stuck fermentation.<sup id="cite_ref-Jackson_3-3" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Glutathione" title="Glutathione">Glutathione</a> (GSH: L-gamma-glutamyl-L-cysteinylglycine) is present in high concentrations up to 10 mM in yeast cells. It assumes a pivotal role in response to sulfur and nitrogen starvation.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Ammonia is not used by bacteria such as <i><a href="/wiki/Acetobacter" title="Acetobacter">Acetobacter</a></i> and the lactic acid bacteria used in <a href="/wiki/Malolactic_fermentation" title="Malolactic fermentation">malolactic fermentation</a>.<sup id="cite_ref-Wine_Micro_2-4" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Importance_in_winemaking">Importance in winemaking</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=4" title="Edit section: Importance in winemaking"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Assimilable nitrogen is an essential nutrient needed by <a href="/wiki/Wine_yeast" class="mw-redirect" title="Wine yeast">wine yeast</a> in order to fully complete fermentation with a minimum amount of undesirable by-products (such as compounds like <a href="/wiki/Hydrogen_sulfide" title="Hydrogen sulfide">hydrogen sulfide</a> that can create off odors) created. Over the course of a fermentation, yeast may use up to a 1000 mg/L of amino acids though often far less than amount is needed.<sup id="cite_ref-Wine_Micro_2-5" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Yeast can store amino acids in intracellular <a href="/wiki/Vacuoles" class="mw-redirect" title="Vacuoles">vacuoles</a> and then later either use them directly, incorporating them into proteins, or break them down and use their carbon and nitrogen components separately.<sup id="cite_ref-Boulton_4-7" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>In the absence of nitrogen, yeast will begin to shut down and die off. Some strains will begin breaking down sulfur containing amino acids like <a href="/wiki/Cysteine" title="Cysteine">cysteine</a> and <a href="/wiki/Methionine" title="Methionine">methionine</a> releasing a sulfur atom that can combine with hydrogen to produce hydrogen sulfide (<span class="chemf nowrap">H<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">2</sub></span></span>S</span>) which can impart rotten egg odors to the wine. However, there is not a direct correlation between YAN levels and hydrogen sulfide production since H<sub>2</sub>S can be produced by yeast even in the presence of abundant nitrogen but with instead other vital nutrients (such as the vitamin <a href="/wiki/Pantothenic_acid" title="Pantothenic acid">pantothenic acid</a>) lacking. There are even some strains of <i>S. cerevisiae</i> that produce H<sub>2</sub>S as a response to having too much available nitrogen (particularly too much glutamic acid and alanine<sup id="cite_ref-Jackson_3-4" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>). This is why a prophylactic approach of indiscriminately adding nitrogen supplementation to every fermentation may not have the desired results of preventing H<sub>2</sub>S.<sup id="cite_ref-Wine_Micro_2-6" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:S_cerevisiae_under_DIC_microscopy.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d9/S_cerevisiae_under_DIC_microscopy.jpg/220px-S_cerevisiae_under_DIC_microscopy.jpg" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d9/S_cerevisiae_under_DIC_microscopy.jpg/330px-S_cerevisiae_under_DIC_microscopy.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d9/S_cerevisiae_under_DIC_microscopy.jpg/440px-S_cerevisiae_under_DIC_microscopy.jpg 2x" data-file-width="1560" data-file-height="1560" /></a><figcaption><i>Saccharomyces cerevisiae</i> can store amino acids in vacuoles until they are needed by the cell.</figcaption></figure> <p>Nitrogen levels in the wine can have an influence on many sensory aspects of the resulting wine, including the synthesis of many aromatic compounds. <a href="/wiki/Fusel_alcohols" class="mw-redirect" title="Fusel alcohols">Fusel alcohols</a> are made by the degradation of amino acids though in the presence of high levels of ammonia and urea their production is reduced. When available nitrogen is limited, the levels of <a href="/wiki/Glycerol" title="Glycerol">glycerol</a> and <a href="/wiki/Trehalose" title="Trehalose">trehalose</a>, which may influence <a href="/wiki/Mouthfeel_(wine)" class="mw-redirect" title="Mouthfeel (wine)">mouthfeel</a>, are higher.<sup id="cite_ref-Jackson_3-5" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Estimates_on_how_much_is_needed">Estimates on how much is needed</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=5" title="Edit section: Estimates on how much is needed"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The amount of YAN needed will depend on what the winemaker's goals are for fermentation, particularly whether or not wild fermentation is desired or if the wine will be fully fermented to dryness. The state of the grapes and the conditions of fermentation will influence the amount of nitrogen needed. Fruit that is damaged, moldy or <a href="/wiki/Botrytis_infected" class="mw-redirect" title="Botrytis infected">botrytis infected</a> will usually be more depleted of nitrogen (as well as other vitamin resources) when they come in from the vineyard than clean, intact grapes. This depletion can be further exacerbated by over <a href="/wiki/Clarification_of_the_must" class="mw-redirect" title="Clarification of the must">clarification of the must</a> and high sugar content. Wines fermented at higher temperatures tend to progress at a faster rate, requiring more nitrogen than longer, cooler fermentation. Also the amount of oxygen exposure will influence the rate of nitrogen uptake by the yeast with wine fermented in complete anaerobic conditions (such as many white wines in stainless steel tanks) requiring less nitrogen than wines fermented in barrels or open top fermentors.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>The suggested range given by enologists varies from 150 mg/L YAN<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> to 400 mg of nitrogen per liter.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Some studies have shown that maximum fermentation rates can be achieved with YAN in the 400 to 500 mg N/L range.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> However, not all winemakers will want to have a fermentation going at maximum rate (in terms of yeast biomass, temperature and speed) due to the impact that it can have on other sensory aspects of the wine such as <a href="/wiki/Aroma_(wine)" class="mw-redirect" title="Aroma (wine)">aroma</a> development and fruit retention.<sup id="cite_ref-Jackson_3-6" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>A study by the <a href="/wiki/UC_Davis_Department_of_Viticulture_and_Enology" title="UC Davis Department of Viticulture and Enology">UC Davis Department of Viticulture and Enology</a> found that recommendations on optimal nitrogen levels to complete a successful fermentation could be made based <a href="/wiki/Harvest_(wine)" title="Harvest (wine)">harvest</a> <a href="/wiki/Brix" title="Brix">brix</a> level which have been adopted by many yeast and nutrient manufacturers.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <ul><li>21°Bx = 200 mg N/L</li> <li>23°Bx = 250 mg N/L</li> <li>25°Bx = 300 mg N/L</li> <li>27°Bx = 350 mg N/L</li></ul> <p>However, other studies have shown successful fermentation be conducted with YAN levels below these recommendations as well as sluggish/stuck fermentations occurring even when YAN levels are in line with recommendations.<sup id="cite_ref-Zoecklein_1-7" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="In_malolactic_fermentation">In malolactic fermentation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=6" title="Edit section: In malolactic fermentation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Malolactic_inoculation_and_nutrient.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Malolactic_inoculation_and_nutrient.JPG/220px-Malolactic_inoculation_and_nutrient.JPG" decoding="async" width="220" height="295" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Malolactic_inoculation_and_nutrient.JPG/330px-Malolactic_inoculation_and_nutrient.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Malolactic_inoculation_and_nutrient.JPG/440px-Malolactic_inoculation_and_nutrient.JPG 2x" data-file-width="1936" data-file-height="2592" /></a><figcaption>Malolactic fermentation inoculum packet and Optimalo, a nutrient supplement that contains amino acids.</figcaption></figure> <p>Like yeast, the lactic acid bacteria (LAB) used in malolactic fermentation (generally <i><a href="/wiki/Oenococcus_oeni" title="Oenococcus oeni">Oenococcus oeni</a></i>) requires nitrogen. However, unlike <i>S. cerevisiae</i> LAB can not utilize ammonia and such additions like diammonium phosphate (DAP) offers no nutritional benefits. Winemakers who inadvertently use DAP as a nutrient additive for their MLF inoculation risk providing nutrients instead for spoilage organisms such as <i><a href="/wiki/Brettanomyces" title="Brettanomyces">Brettanomyces</a></i>.<sup id="cite_ref-Wine_Micro_2-7" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>While some winemakers will inoculate their LAB with nutrients that include nitrogen, most of the nutrients needed for MLF come from the breakdown (or <a href="/wiki/Autolysis_(wine)" class="mw-redirect" title="Autolysis (wine)">autolysis</a>) of the dead yeast cells. Additionally, most bacteria used in MLF have the ability to produce extracellular protease enzymes that can also breakdown larger peptide chains into their base amino acid residues that can then be used for metabolism.<sup id="cite_ref-Boulton_4-8" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Measurements_and_tests">Measurements and tests</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=7" title="Edit section: Measurements and tests"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The nitrogen by <a href="/wiki/O-phthaldialdehyde" class="mw-redirect" title="O-phthaldialdehyde">o-phthaldialdehyde</a> assay (NOPA) is used to measured available primary amino acids in grape juice using a <a href="/wiki/Spectrophotometer" class="mw-redirect" title="Spectrophotometer">spectrophotometer</a> that can measure at 335 nm <a href="/wiki/Wavelength" title="Wavelength">wavelengths</a>. Since the assay only measures primary amino acids, the results produces won't include proline or ammonia concentrations.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Proline can be separately measured with an assay that uses <a href="/wiki/Ninhydrin" title="Ninhydrin">ninhydrin</a> to react with the amino acid in the presence of <a href="/wiki/Formic_acid" title="Formic acid">formic acid</a>, yielding a compound that can be absorbed at 517 nm.<sup id="cite_ref-Zoecklein_1-8" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Spectrophotometer_small_for_8_samples-01.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Spectrophotometer_small_for_8_samples-01.jpg/220px-Spectrophotometer_small_for_8_samples-01.jpg" decoding="async" width="220" height="213" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Spectrophotometer_small_for_8_samples-01.jpg/330px-Spectrophotometer_small_for_8_samples-01.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Spectrophotometer_small_for_8_samples-01.jpg/440px-Spectrophotometer_small_for_8_samples-01.jpg 2x" data-file-width="1935" data-file-height="1874" /></a><figcaption>YAN levels can be measured using the NOPA assay and a spectrophotometer.</figcaption></figure> <p><a href="/wiki/Formol_titration" class="mw-redirect" title="Formol titration">Formol titration</a>, invented by the Danish chemist <a href="/wiki/S._P._L._S%C3%B8rensen" title="S. P. L. Sørensen">S. P. L. Sørensen</a> in 1907, utilizes <a href="/wiki/Formaldehyde" title="Formaldehyde">formaldehyde</a> in the presence of <a href="/wiki/Potassium_hydroxide" title="Potassium hydroxide">potassium</a> or <a href="/wiki/Sodium_hydroxide" title="Sodium hydroxide">sodium hydroxide</a> to measure amino acid concentration and ammonia with the aid of a <a href="/wiki/PH_meter" title="PH meter">pH meter</a>. The reagents will also react with proline which can give a slightly higher YAN measurement than NOPA.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> The Formal method also has the disadvantages of involving the use and disposal of formaldehyde which is a known <a href="/wiki/Carcinogen" title="Carcinogen">carcinogen</a><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> and the highly toxic reagent <a href="/wiki/Barium_chloride" title="Barium chloride">barium chloride</a>.<sup id="cite_ref-Zoecklein_1-9" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Ammonia and ammonium can be measurement using an ion-selective electrode probe and a pH meter.<sup id="cite_ref-Zoecklein_1-10" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Nitrogen_supplementation">Nitrogen supplementation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=8" title="Edit section: Nitrogen supplementation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Winemakers have long known that some fermentations ran more predictable and "healthier" if <a href="/wiki/Pomace" title="Pomace">pomace</a> (the solid skins, seeds and remains left after <a href="/wiki/Pressing_(wine)" title="Pressing (wine)">pressing</a>) from another wine was added to the batch. This is a method still used today to make the <a href="/wiki/Italian_wine" title="Italian wine">Italian wine</a> <i><a href="/wiki/Ripasso" class="mw-redirect" title="Ripasso">Ripasso</a></i>. In 14th century <a href="/wiki/Tuscany_(wine)" class="mw-redirect" title="Tuscany (wine)">Tuscany</a>, the technique of <a href="/wiki/Governo" title="Governo">governo</a> used in <a href="/wiki/History_of_chianti" class="mw-redirect" title="History of chianti">some of the earliest Chiantis</a> involved adding dried grapes to the batch.<sup id="cite_ref-Johnson_16-0" class="reference"><a href="#cite_note-Johnson-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> While that also added sugar both methods provided extra nitrogen and other nutrients still available in the skins and seeds.<sup id="cite_ref-Oxford_pg_319_17-0" class="reference"><a href="#cite_note-Oxford_pg_319-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:NH2CONH2.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/NH2CONH2.png/220px-NH2CONH2.png" decoding="async" width="220" height="97" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/NH2CONH2.png/330px-NH2CONH2.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/98/NH2CONH2.png/440px-NH2CONH2.png 2x" data-file-width="628" data-file-height="276" /></a><figcaption>Urea.</figcaption></figure> <p>As <a href="/wiki/Enologist" class="mw-redirect" title="Enologist">enologists</a> began better understanding the science of fermentation, nitrogen was identified as a principal nutrient and winemakers as early as the 1900s began adding ammonium salts to their must.<sup id="cite_ref-Boulton_4-9" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Urea" title="Urea">Urea</a> was also used as an early nitrogen supplement but research linking it to the development of <a href="/wiki/Ethyl_carbamate" title="Ethyl carbamate">ethyl carbamate</a> has led to its banning in many countries, including the <a href="/wiki/United_States_(wine)" class="mw-redirect" title="United States (wine)">United States</a> since 1990.<sup id="cite_ref-Wine_Micro_2-8" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>There are many types of nitrogen supplements available for winemakers to use. Most of them are complex formulations that include nitrogen (from either amino acids or ammonium salts) along with vitamins, minerals and other growth factors and sold under brand names like <i>Go-Ferm</i>, <i>Superfood</i>, <i>Fermaid K</i> (the later two also containing some DAP).<sup id="cite_ref-Wine_Micro_2-9" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Amino acids can be added directly to the must though as of 2010 only <a href="/wiki/Glycine" title="Glycine">glycine</a> is permitted to be added to must in the United States.<sup id="cite_ref-Boulton_4-10" class="reference"><a href="#cite_note-Boulton-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Ferm-O_yeast_hull_mixture.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/Ferm-O_yeast_hull_mixture.JPG/220px-Ferm-O_yeast_hull_mixture.JPG" decoding="async" width="220" height="164" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/Ferm-O_yeast_hull_mixture.JPG/330px-Ferm-O_yeast_hull_mixture.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/41/Ferm-O_yeast_hull_mixture.JPG/440px-Ferm-O_yeast_hull_mixture.JPG 2x" data-file-width="2592" data-file-height="1936" /></a><figcaption>Fermaid-O is nitrogen supplement containing yeast hulls (a source of amino acids) and other vitamins but no diammonium phosphate.</figcaption></figure> <p>Yeast hulls (or Yeast ghosts) are the remnants of yeast cell walls left over from the commercial production of yeast strains to be used for inoculation. In addition to providing a source of assimilable nitrogen from amino acids, they also provide <a href="/wiki/Lipids" class="mw-redirect" title="Lipids">lipids</a> and <a href="/wiki/Sterols" class="mw-redirect" title="Sterols">sterols</a> that can be used by the cells to strengthen their plasma membrane, allowing for the uptake of other sources of nitrogen.<sup id="cite_ref-Wine_Micro_2-10" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Risk_in_adding_too_much">Risk in adding too much</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=9" title="Edit section: Risk in adding too much"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Nitrogen supplements, particularly DAP, stimulates yeast reproduction and can greatly increase the biomass. This could have the consequence of speeding up the fermentation rate faster than what a winemaker may desire and will also increase the fermentation temperature due to the heat being generated by the yeast. The excess biomass can also create a scarcity of other yeast nutrients, such a vitamins and sterols, due to increase competition and may lead to the production of off-odors (such as hydrogen sulfide) and even stuck fermentations.<sup id="cite_ref-Zoecklein_1-11" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Excessive levels of the amino acid arginine (greater than 400 mg/L), especially near the end of fermentation, can pose the risk increase the production of ethyl carbamate. This is because arginine gets broken down into urea which can be reabsorbed and utilized by yeast or metabolized into ammonia. However, urea also reacts with <a href="/wiki/Ethanol" title="Ethanol">ethanol</a> if it is not completely metabolized which coupled with long term exposure (as well as high temperatures) can lead to the production of the <a href="/wiki/Ester" title="Ester">ester</a> ethyl carbamate.<sup id="cite_ref-Zoecklein_1-12" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/86/Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG/220px-Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/86/Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG/330px-Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/86/Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG/440px-Aspect_de_brettanomyces_bruxellensis_sur_g%C3%A9lose_YPD.JPG 2x" data-file-width="1280" data-file-height="960" /></a><figcaption><i>Brettanomyces</i> is one spoilage organism that can take advantage of excess nitrogen supplementation left in the wine.</figcaption></figure> <p>However, the greatest risk of over supplementing a must is that excess nitrogen and other nutrients will be left behind after fermentation is complete. This can create microbial instability as spoilage organisms can use these excess nutrients.<sup id="cite_ref-Jackson_3-7" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Wine_laws_and_regulations">Wine laws and regulations</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=10" title="Edit section: Wine laws and regulations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the United States, the <a href="/wiki/Alcohol_and_Tobacco_Tax_and_Trade_Bureau" title="Alcohol and Tobacco Tax and Trade Bureau">Alcohol and Tobacco Tax and Trade Bureau</a> (TTB) limits the use of diammonium phosphate as a nitrogen additive to 968 mg/L (8 lbs/1000 gal) which provides 203 mg N/L of YAN. In the <a href="/wiki/European_Union" title="European Union">European Union</a>, most countries follow the guidelines of the <a href="/wiki/International_Organisation_of_Vine_and_Wine" title="International Organisation of Vine and Wine">International Organisation of Vine and Wine</a> (OIV) which dictates a limit of 300 mg/L. In <a href="/wiki/Australia_(wine)" class="mw-redirect" title="Australia (wine)">Australia</a>, the limit is based on the level of inorganic <a href="/wiki/Phosphate" title="Phosphate">phosphate</a> with a maximum limit of 400 mg/L of phosphate permitted.<sup id="cite_ref-Wine_Micro_2-11" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Influence_of_timing">Influence of timing</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=11" title="Edit section: Influence of timing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As most nutrient supplements feed all living microorganism in the must (whether desirable or not), winemakers will often wait to add the nutrients until they are ready to inoculate the must with their desired <i>S. cerevisiae</i> strain. Producers who are using wild ferments may also wait until after <a href="/wiki/Sulfur_dioxide" title="Sulfur dioxide">sulfur dioxide</a> additions have killed off unwanted microbes or feed early because they would like the potential complexity that other microbes could add to the wine. When added, the nitrogen is usually in the form of amino acids, combined with vitamins and minerals to help kick start the fermentation.<sup id="cite_ref-Wine_Micro_2-12" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Yeast_and_nutrients.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Yeast_and_nutrients.JPG/220px-Yeast_and_nutrients.JPG" decoding="async" width="220" height="148" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Yeast_and_nutrients.JPG/330px-Yeast_and_nutrients.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Yeast_and_nutrients.JPG/440px-Yeast_and_nutrients.JPG 2x" data-file-width="664" data-file-height="446" /></a><figcaption>When yeast inoculum <i>(left)</i> is first rehydrated, the ammonium salts in DAP would be too toxic so winemakers will often use a nutrient supplement <i>(right)</i> that contains primarily amino acids as the nitrogen source.</figcaption></figure> <p>Soon after inoculation, yeast begin to rapidly consume the available assimilable nitrogen with up to 46% of YAN being fully consumed by the onset of full fermentation.<sup id="cite_ref-Zoecklein_1-13" class="reference"><a href="#cite_note-Zoecklein-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Because inorganic nitrogen, such as the ammonium salts in DAP, are toxic to yeast in high levels, it is never added during inoculation when the biomass of the newly re-hydrated yeast is low. Many winemakers split up the dosage of DAP with the first addition being made at the end of the <a href="/wiki/Lag_phase" class="mw-redirect" title="Lag phase">lag phase</a> when the yeast enter their period of exponential growth and alcoholic fermentation begins. In most must this is around 48 to 72 hours after inoculation. A second dosage is then often added around a third of the way through sugar fermentation and often before the sugar levels hit 12-10 Brix (6.5 to 5.5 Baumé, 48.3 to 40.0 Oechsle) because as the fermentation progresses yeast cells are no longer able to bring the nitrogen into the cell due to the increasing toxicity of ethanol surrounding the cells. This leaves the nitrogen unused and available for spoilage organisms that may come afterwards.<sup id="cite_ref-Wine_Micro_2-13" class="reference"><a href="#cite_note-Wine_Micro-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Jackson_3-8" class="reference"><a href="#cite_note-Jackson-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Yeast_assimilable_nitrogen&action=edit&section=12" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-Zoecklein-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Zoecklein_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-8"><sup><i><b>i</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-9"><sup><i><b>j</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-10"><sup><i><b>k</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-11"><sup><i><b>l</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-12"><sup><i><b>m</b></i></sup></a> <a href="#cite_ref-Zoecklein_1-13"><sup><i><b>n</b></i></sup></a></span> <span class="reference-text">B. Zoecklein, K. Fugelsang, B. Gump, F. Nury <i>Wine Analysis and Production</i> pgs 152-163, 340-343, 444-445, 467 Kluwer Academic Publishers, New York (1999) <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0834217015" title="Special:BookSources/0834217015">0834217015</a></span> </li> <li id="cite_note-Wine_Micro-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-Wine_Micro_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-8"><sup><i><b>i</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-9"><sup><i><b>j</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-10"><sup><i><b>k</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-11"><sup><i><b>l</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-12"><sup><i><b>m</b></i></sup></a> <a href="#cite_ref-Wine_Micro_2-13"><sup><i><b>n</b></i></sup></a></span> <span class="reference-text">K. 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Edwards <i>Wine Microbiology</i> Second Edition pgs 16-17, 35, 115-117, 124-129 Springer Science and Business Media , New York (2010) <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0387333495" title="Special:BookSources/0387333495">0387333495</a></span> </li> <li id="cite_note-Jackson-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Jackson_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Jackson_3-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Jackson_3-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Jackson_3-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Jackson_3-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Jackson_3-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Jackson_3-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Jackson_3-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-Jackson_3-8"><sup><i><b>i</b></i></sup></a></span> <span class="reference-text">R. Jackson <i>"Wine Science: Principles and Applications"</i> Third Edition pgs 90-98, 151, 167, 183, 305-310, 356-357, 375-387, 500, 542 Academic Press 2008 <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780123736468" title="Special:BookSources/9780123736468">9780123736468</a></span> </li> <li id="cite_note-Boulton-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-Boulton_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Boulton_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Boulton_4-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Boulton_4-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Boulton_4-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Boulton_4-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Boulton_4-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Boulton_4-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-Boulton_4-8"><sup><i><b>i</b></i></sup></a> <a href="#cite_ref-Boulton_4-9"><sup><i><b>j</b></i></sup></a> <a href="#cite_ref-Boulton_4-10"><sup><i><b>k</b></i></sup></a></span> <span class="reference-text">R. Boulton, V. Singleton, L. Bisson, R. Kunkee <i>Principles and Practices of Winemaking</i> pgs 46-48, 80-81, 153-167, 256 Springer 1996 New York <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-4419-5190-8" title="Special:BookSources/978-1-4419-5190-8">978-1-4419-5190-8</a></span> </li> <li id="cite_note-Spayd-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Spayd_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Spayd_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Sara E. Spayd and Joy Andersen-Bagge <i>"<a rel="nofollow" class="external text" href="http://ajevonline.org/content/47/4/389.abstract">Free Amino Acid Composition of Grape Juice From 12 Vitis vinifera Cultivars in Washington</a>"</i> Am. J. Enol. Vitic 1996 vol. 47 no. 4 389-402</span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPenninckx2002" class="citation journal cs1">Penninckx, MJ (2002). <a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fs1567-1356%2802%2900081-8">"An overview on glutathione in Saccharomyces versus non-conventional yeasts"</a>. <i>FEMS Yeast Research</i>. <b>2</b> (3): 295–305. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fs1567-1356%2802%2900081-8">10.1016/s1567-1356(02)00081-8</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12702279">12702279</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=FEMS+Yeast+Research&rft.atitle=An+overview+on+glutathione+in+Saccharomyces+versus+non-conventional+yeasts&rft.volume=2&rft.issue=3&rft.pages=295-305&rft.date=2002&rft_id=info%3Adoi%2F10.1016%2Fs1567-1356%2802%2900081-8&rft_id=info%3Apmid%2F12702279&rft.aulast=Penninckx&rft.aufirst=MJ&rft_id=https%3A%2F%2Fdoi.org%2F10.1016%252Fs1567-1356%252802%252900081-8&rfr_id=info%3Asid%2Fen.wikipedia.org%3AYeast+assimilable+nitrogen" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">Lallemand <i>"<a rel="nofollow" class="external text" href="http://www.vawa.net/winemaking-articles/Lallemand%20Yeast%20Nutrition.pdf">Yeast Nutrition and Protection for Reliable Alcoholic Fermentations</a>"</i> The State of The Art. Accessed: March 31st, 2013</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">S.M. Weeks and P.A. Henschke <i>"<a rel="nofollow" class="external text" href="https://www.awri.com.au/commercial_services/analytical_services/analyses/yeast_assimilable_nitrogen/yeast-assimilable-nitrogen-3/">Yeast assimilable nitrogen</a>"</i> The Australian Wine Research Institute. Accessed: March 31st, 2013</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">Maurizio Ugliano, Paul A. Henschke, Markus J. Herderich, Isak S. Pretorius <i>"<a rel="nofollow" class="external text" href="http://www.newworldwinemaker.com/pdf/awri_nitrogen_management_report_22.pdf">Nitrogen management is critical for wine flavour and style</a>"</i> The Australian Wine Research Institute. VOL 22 NO 6 NOVEMBER/DECEMBER 2007</span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text">Bruce W. Zoecklein <i>"<a rel="nofollow" class="external text" href="http://www.apps.fst.vt.edu/extension/enology/VC/July-aug98.html">I. Nitrogen Compounds</a>"</i> Vintner's Corner, Virginia Tech University Enology Notes, Vol. 13, No. 4 July - August, 1998</span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text">Linda F. Bisson and Christian E. Butzke <i>"<a rel="nofollow" class="external text" href="http://ajevonline.org/content/51/2/168.abstract">Diagnosis and Rectification of Stuck and Sluggish Fermentations</a>"</i> Am. J. Enol. Vitic 2000 vol. 51 no. 2 168-177</span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text">Chris Gerling "<i><a rel="nofollow" class="external text" href="http://www.fruit.cornell.edu/shared/pdfs/FAQYAN.pdf">FAQs about YAN</a>"</i> Veraison to Harvest #6, Cornell University Cooperative Extension. October 2010</span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text">UC Davis Cooperative Extension <i>"<a rel="nofollow" class="external text" href="http://www.foodsci.purdue.edu/research/labs/enology/NOPA98.pdf">NOPA Procedure</a>"</i> Butzke & Dukes (1998) Accessed: March 31st, 2013</span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text">Barry H. Gump, Bruce W. Zoecklein, Kenneth C. Fugelsang and Robert S. Whiton <i>"<a rel="nofollow" class="external text" href="http://ajevonline.org/content/53/4/325.abstract?related-urls=yes&legid=ajev;53/4/325">Comparison of Analytical Methods for Prediction of Prefermentation Nutritional Status of Grape Juice</a>"</i> Am. J. Enol. Vitic 2002 vol. 53 no. 4 325-329</span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">Virginia Tech University <i>"<a rel="nofollow" class="external text" href="http://www.apps.fst.vt.edu/extension/enology/downloads/FermNitro.pdf">Estimate of FAN by Formol Titration</a>"</i> Adapted from Zoecklein et al., 1999 and Gump, Zoecklein and Fugelsang, 2002. Accessed: March 31st, 2013</span> </li> <li id="cite_note-Johnson-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-Johnson_16-0">^</a></b></span> <span class="reference-text">H. Johnson <i>Vintage: The Story of Wine</i> pg 415 Simon and Schuster 1989 <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-671-68702-6" title="Special:BookSources/0-671-68702-6">0-671-68702-6</a></span> </li> <li id="cite_note-Oxford_pg_319-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-Oxford_pg_319_17-0">^</a></b></span> <span class="reference-text">J. Robinson (ed) <i>"The Oxford Companion to Wine"</i> Third Edition pg 319 Oxford University Press 2006 <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-19-860990-6" title="Special:BookSources/0-19-860990-6">0-19-860990-6</a></span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text">CHRISTIAN E. BUTZKE & LINDA F. BISSON <i>"<a rel="nofollow" class="external text" href="https://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM119802.pdf">Ethyl Carbamate Preventative Action Manual</a>"' UC Davis Cooperative Extension. Accessed: March 31st, 2013</i></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text">M. Ellin Doyle, Carol E. Steinhart and Barbara A. Cochrane <i>"<a rel="nofollow" class="external text" href="https://books.google.com/books?id=S28jeel2VfUC&dq=adding+urea+to+wine+fermentation&pg=PA297">Food safety:1994</a>"</i> pg 297, Food Research Institute University of Wisconsin-Madison, CRC Press (1994) <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0824792904" title="Special:BookSources/0824792904">0824792904</a></span> </li> </ol></div></div> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline 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style="width:1%"><a href="/wiki/Fermentation_in_winemaking" title="Fermentation in winemaking">Fermentation</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Malolactic_fermentation" title="Malolactic fermentation">Malolactic fermentation</a></li> <li><a href="/wiki/Sparkling_wine_production" title="Sparkling wine production">Sparkling wine production</a></li> <li><a href="/wiki/Sugars_in_wine" title="Sugars in wine">Sugars in wine</a></li> <li><a href="/wiki/S%C3%BCssreserve" class="mw-redirect" title="Süssreserve">Süssreserve</a></li> <li><a href="/wiki/Traditional_method" title="Traditional method">Traditional method</a></li> <li><a class="mw-selflink selflink">Yeast assimilable nitrogen</a></li> <li><a href="/wiki/Yeast_in_winemaking" title="Yeast in winemaking">Yeast in winemaking</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a 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