Flavonol haze in white wines

  • T. C. Somers
  • G. Ziemelis
Keywords: wine disorder, analysis, phenol, grape harvest, technique, leaf


The formation of a yellow haze in commercial white wines, and of yellow sediments from both juices and wines, was due to precipitation of quercetin. The vine leaves were found to be the major source of soluble quercetin glycosides, leading to excessive levels of free quercetin after hydrolysis during juice or wine storage. Flavonols were analysed by reversed-phase HPLC. Widespread use of machine harvesting, with higher leaf contamination of the grape crush, is considered to be the primary cause of this new form of wine instability. An enzymatic procedure for detecting susceptibility to such deposition in juices and wines is described.