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In defense of the Adams-Harbertson assay
A recently published article in the Journal of AOAC International by Larry Brooks, Leo McCloskey and other consultants claims to show that the Adams-Harbertson tannin assay cannot provide winemakers with useful data, due to a lack of precision and reproducibility in some winery laboratories.
The Adams-Harbertson tannin assay, reported in 1999, is a direct adaptation of the Hagerman-Butler method, widely used for over 30 years. The assay is designed to provide wineries with an inexpensive, reliable and readily accessible measurement of tannin. The method was extensively tested and improved, with thousands of trials over several years, before it was reported.
It has been widely adopted at many wineries as a robust method with remarkably high precision (3-5%) between replicates, even over a period of months. It has also been used as a reference method for other techniques. The assay has also been adopted by at least one highly respected winery service lab, which offers this procedure to its clients.
Like any analytical procedure, the Adams-Harbertson tannin assay requires time and effort to ensure that a specific lab or analyst can provide reproducible results. Regular comparisons of routine assays between winery labs show large variations--up to 20% in some cases.
The Department of Viticulture and Enology recommends that the lab or analyst wishing to use this procedure first be provided with training. Tannins are astringent, bitter plant polyphenols that either bind or precipitate proteins. This binding can be related to the sensation of astringency, and a strong correlation has been shown for the Adams-Harbertson assay and astringency in wine.
Brooks et al's claim of the failure of the Adams-Harbertson tannin assay, due to large variation between non-accredited winery labs, has demonstrated lab performance fallibility, not method invalidity. Their claim is baseless, and the Department of Viticulture and Enology stands behind Dr. Adams, his research, and the value of this assay.
It is our mission to provide the California grape and wine industry with innovation that will improve product quality and sustainability. Discoveries are always made public with full disclosure of procedures and claims, to allow for as wide an adoption as possible. One of the goals is to provide new technology in the form of more informative and less costly analyses, which can in some cases disruptively displace existing technology or services. We are proud that the Adams-Harbertson tannin assay is used today in many wineries to make critical winemaking decisions. To review the video presentation of the entire RAVE 2007 program on the Adams- Harbertson assay, visit: webcast.ucdavis.edu/viten/2007/.
Andrew Waterhouse, chair
Department of Viticulture & Enology University of California, Davis
A recently published article in the Journal of AOAC International by Larry Brooks, Leo McCloskey and other consultants claims to show that the Adams-Harbertson tannin assay cannot provide winemakers with useful data, due to a lack of precision and reproducibility in some winery laboratories.
The Adams-Harbertson tannin assay, reported in 1999, is a direct adaptation of the Hagerman-Butler method, widely used for over 30 years. The assay is designed to provide wineries with an inexpensive, reliable and readily accessible measurement of tannin. The method was extensively tested and improved, with thousands of trials over several years, before it was reported.
It has been widely adopted at many wineries as a robust method with remarkably high precision (3-5%) between replicates, even over a period of months. It has also been used as a reference method for other techniques. The assay has also been adopted by at least one highly respected winery service lab, which offers this procedure to its clients.
Like any analytical procedure, the Adams-Harbertson tannin assay requires time and effort to ensure that a specific lab or analyst can provide reproducible results. Regular comparisons of routine assays between winery labs show large variations--up to 20% in some cases.
The Department of Viticulture and Enology recommends that the lab or analyst wishing to use this procedure first be provided with training. Tannins are astringent, bitter plant polyphenols that either bind or precipitate proteins. This binding can be related to the sensation of astringency, and a strong correlation has been shown for the Adams-Harbertson assay and astringency in wine.
Brooks et al's claim of the failure of the Adams-Harbertson tannin assay, due to large variation between non-accredited winery labs, has demonstrated lab performance fallibility, not method invalidity. Their claim is baseless, and the Department of Viticulture and Enology stands behind Dr. Adams, his research, and the value of this assay.
It is our mission to provide the California grape and wine industry with innovation that will improve product quality and sustainability. Discoveries are always made public with full disclosure of procedures and claims, to allow for as wide an adoption as possible. One of the goals is to provide new technology in the form of more informative and less costly analyses, which can in some cases disruptively displace existing technology or services. We are proud that the Adams-Harbertson tannin assay is used today in many wineries to make critical winemaking decisions. To review the video presentation of the entire RAVE 2007 program on the Adams- Harbertson assay, visit: webcast.ucdavis.edu/viten/2007/.
Andrew Waterhouse, chair
Department of Viticulture & Enology University of California, Davis
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