Yeast assimilable nitrogen

Red wine fermenting just after pigeage

Viognier pomace after pressing

Cell membrane detailed diagram en

DAP addition before and after

S cerevisiae under DIC microscopy

Malolactic inoculation and nutrient

Yeast assimilable nitrogen (YAN) is a critical component in the fermentation process, particularly in the production of wine and beer. YAN refers to the sum of free amino nitrogen (FAN), ammonia (NH3), and small peptides that are available for yeast metabolism during fermentation. Adequate levels of YAN are essential for healthy yeast growth and the prevention of fermentation problems.

Components of YAN

YAN is composed of several nitrogenous compounds that yeast can assimilate:

• Free Amino Nitrogen (FAN): This includes amino acids and small peptides that yeast can directly uptake and utilize.
• Ammonia (NH3): A simple nitrogen source that yeast can readily assimilate.
• Small Peptides: Short chains of amino acids that can be broken down by yeast enzymes.

Importance in Fermentation

During the fermentation process, yeast requires nitrogen to synthesize proteins, nucleic acids, and other cellular components. Insufficient YAN can lead to:

• Stuck or sluggish fermentation
• Production of undesirable sulfur compounds
• Poor yeast health and viability

Conversely, excessive YAN can result in the production of unwanted by-products such as ethyl carbamate, a potential carcinogen.

Measurement of YAN

YAN can be measured using several methods, including:

• Formol titration
• Ninhydrin assay
• Enzymatic methods
• High-performance liquid chromatography (HPLC)

Management of YAN in Winemaking

Winemakers often monitor and adjust YAN levels to ensure optimal fermentation. This can be done by:

• Adding diammonium phosphate (DAP)
• Using nutrient blends that contain amino acids and vitamins
• Managing vineyard practices to influence grape nitrogen content

Related Pages

• Fermentation
• Yeast
• Wine chemistry
• Beer brewing
• Amino acids
• Sulfur compounds

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