title: Pyruvate scale
text: # Pyruvate scale
  
  The pyruvate scale measures pungency in onions and garlic with units of $μmol/g_{fw}$ (micromoles per gram fresh weight). It is named after pyruvic acid, the alpha-keto acid co-product created in the biochemical pathway that forms syn-propanethial-S-oxide, the main lachrymatory agent in onions.
  
  ## Examples
  
  The standard onion has an eight rating, while "sweet onions" have a two or three rating on the scale. The lower the score or scale the more "sweet" the onions are rated. Anything less than five is considered a sweet onion. The Vidalia onion variety is considered sweet and must have a score of 5.0 $μmol/g_{fw}$ or less. The Supasweet onion (usually grown in Lincolnshire, England) registers 1.5 to 2 on the scale. A standard brown onion is usually in the range of 6–7 out of 10.
  
  ## Influential factors
  
  Soil type, rain, and sunlight affect the pungency in onions and garlic and, therefore, their score on the pyruvate scale.
  
  