Ultraviolet absorption (UV absorbance)

Ultraviolet absorption is an index showing how much light of a specific wavelength (mainly 280 nm) is absorbed when it is shone through sake. This absorbance reflects the amount of aromatic amino acids in the sake (specifically tyrosine, tryptophan, and phenylalanine), and is closely related to the sake's amino acid content, degree of coloration, and buffering capacity. In commercially available sake, ultraviolet absorption values generally cover a fairly wide range, from 2.0 to 6.5. Measuring this index helps in evaluating the quality and characteristics of sake.