Analysis of grape and wine tannins: Methods, applications and challenges

Tannins are polyphenolic secondary metabolites, which can be found in many higher plants and are identified by their ability to complex with and precipitate proteins. This key property is believed to be responsible for the mouth-feel and astringency caused by wine tannins. The analysis of tannins is of interest to practitioners in a diverse range of fields, including chemistry, pharmacology, food science, animal nutrition, ecology and plant physiology. There is a desire within the Australian wine industry to exploit objective tannin measures to complement human sensory assessment for style and quality specifications. This review, therefore, concentrates on grape-derived condensed tannins, also known as proanthocyanidins, and wine tannins formed from grape tannins. We summarise recent advances with the development of analytical methods for the quantification of tannins, review techniques for the structural characterisation of tannin molecules and emphasise the need to refine these techniques.