Progress 10/01/99 to 09/30/04
Outputs
The color due to copigmentation has been shown to be the more significant than either that due to ionized anthocyanins or polymeric pigment in young red wines. The variation between grapes in terms of the incidence and levels of copigmentation cofactors, and the color due to copigmentation has been studied. The levels of copigmentation in several hundred wines ranging from California and dozens of Italian wines from Marche and Tuscany have been measured and correlated with analytical measures of individual components. Prediction functions for the color due to copigmentation, based solely on anthocyanin and phenolic composition have been developed and tested successfully. Preliminary studies of the formation of polymeric pigment, associated with the decline of copigmented color have been completed. Alternative rapid spectroscopic methods such as NIR and FTIR in the MIR region have been applied to the quantification of the color due to copigmentation, free anthocyanins
and polymeric pigment.
Impacts
The rates of formation of polymeric pigment has been followed in a small number of Cabernet Sauvignon wines from the 2002 harvest, at two temperatures (20 and 40 C), over a six month period. The depletion of monomeric anthocyanin and uncolored tannin was followed with the formation of polymeric pigment. The corresponding color changes were also measured. A thesis is in preparation. A more extensive study using 30 wines from the 2003 harvest, and studying three temperatures is underway. Similar monomeric and polymeric composition is being followed, together with the corresponding color changes. A mathematical model for the polymerization kinetic will be evaluated the across the temperature range (20, 30 and 40 C).
Publications
- Boselli, E., R. B. Boulton, J. H. Thorngate and N. G. Frega. Chemical and sensory characterization of DOC red wines from Marche (Italy) related to aging and grape cultivars. J. Agric. Food Chem. 52:3843-3854 (2004).
- Boulton, R. B. The Copigmentation of Anthocyanins and Its Role in the Color of Red Wine: A Critical Review. Am. J. Enol. Vitic. 52:67- 87 (2001).
- Boulton, R. B. Predicting The Color of Red Wines. Honorary Research Lecture Am. Soc. Enol. Vitic. Ann. Mtg. (2003).
- Darius-Martin, J., M. Carrillo, E. Diaz and R. B. Boulton. Enhancement of red wine color by pre-fermentation additions of copigments. Food Chem. 73:217-220 (2001). Levengood, J. A Survey of Copigmentation in Cabernet Sauvignon Wines. M. S. Thesis, University of California, Davis, CA (1996).
- Levengood, J. S. and R. B. Boulton. The variation in color due to copigmentation in young Cabernet sauvignon wines and the influence of some viticultural and enological factors. In: Red Wine Color Ed. A. L Waterhouse and K.A. Kennedy, ACS Symposium Series # 886, Am. Chem. Soc. Washington, (2004), 53-67.
- Sitton, G. The Role of Skin and Seed Removal on the Color of Red Wines. M. S. Thesis, University of California, Davis, CA (1999).
- Vaadia, M. Copigmentation in Varietal Wines from the Napa Valley. M. S. Thesis, University of California, Davis, CA (1997).
- Versari, A., J. Thorngate and R. B. Boulton. The prediction of color components of red wines using ultra-violet, visible and infrared spectra and the method of partial least squares. In: Red Wine Color Ed. A. L Waterhouse and K.A. Kennedy, ACS Symposium Series # 886, Am. Chem. Soc. Washington, (2004), 35-52.
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Progress 01/01/03 to 12/31/03
Outputs
The research projects in progress are two that are involved with studies of the formation of polymeric pigment in red wines and another involving copigmentation due to the addition of limited amounts of white skins, prior to fermentation, which has been completed. The color of red wine is of major importance in commercial winemaking, since it is the first sensory signal that consumers receive when a red wine is presented to them. The copigmentation study has focused on the use of a small amount of white grape skins mixed in with the red grape skins, generally referred to as co-fermentation. The practice of co-fermenting a small amount of white skins with mostly red grapes is not new and has historical practice in the Chianti region of Italy, in the Rhone Valley of France and in the Rioja district of Spain. The optimal proportion of white skins has not been studied extensively, not at all under Californian conditions. The thesis has been completed and the findings
presented at a national meeting. The prediction of aged wine color cannot be anticipated from young wine composition at present. As such the influence of treatments that alter color in the short term cannot be extrapolated to see the effects in the wine after it has been aged. The present direction aims to relate young wine composition to aged wine composition by way of kinetic descriptions of the polymerization rates. This is being tested over the first six months after fermentation during which almost 50% of the polymer is formed at cellar temperatures.
Impacts
The rates of formation of polymeric pigment has been followed in a small number of Cabernet Sauvignon wines from the 2002 harvest, at two temperatures (20 and 40 C), over a six month period. The depletion of monomeric anthocyanin and uncolored tannin was followed with the formation of polymeric pigment. The corresponding color changes were also measured. A thesis is in preparation. A more extensive study using 30 wines from the 2003 harvest, and studying three temperatures is underway. Similar monomeric and polymeric composition is being followed, together with the corresponding color changes. A mathematical model for the polymerization kinetic will be evaluated the across the temperature range (20, 30 and 40 C).
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
The projects supported in part during this period have been two that are involved with studies of the copigmentation phenomenon in red wines. The color of red wine is of major importance in commercial winemaking, since it is the first sensory signal that consumers receive when a red wine is presented to them. One study has focused on the use of a small amount of white grape skins mixed in with the red grape skins, generally referred to as co-fermentation. Another has been studying the variation between berries within a single cluster, with an emphasis on the distribution of pigments and copigmentation cofactors. The practice of co-fermentation of a small amount of white skins with mostly red grapes is not new and has historical practice in the Chianti region of Italy, in the Rhone Valley of France and in the Rioja district of Spain. The optimal proportion of white skins has not been studied extensively, not at all under Californian conditions. The two mixtures studied
are Pinot Gris with Pinot Noir and Malvasia Bianca with Sangiovese, with levels of 5 and 10% by weight and controls. The monomeric phenols and pigments are being analysed, together with other extractive such as tannin and polymeric pigments. The work is in progress.
Impacts
The distribution of pigments and copigmentation cofactors (the colorless phenolic compounds that enable the copigmentation) within a cluster were measured by mapping the 120 berries on a cluster of Cabernet Sauvignon, peeling the skins and performing single berry extracts. These were analyzed for all monomeric phenols and anthocyanins, the mean and the variance calculated and a cluster map created for each of the major components. The variance within a cluster is essential to understand how many berries should be sampled if reliable phenolic measurements are to be made. A thesis has been completed and the study presented to a national meeting.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
The studies thus far, have addressed the development of the cofactors in maturing grapes and the behavior of copigmented color during various wine treatments by identifying the major copigmentation cofactors involved in the color of red wine, in addition to determining their abundance in the major wine grape culitvars. The general importance of copigmentation to the color is the economically significant cultivars, Sangiovese from Italy, and Tempranillor and Grenache from Spain. These cultivars are experiencing a renewed interest in California, and have been characterized as having poor color and color stability. The project continues to develop prediction methodologies for the level of copigmentation in wines, based on grape composition, by development the relationships between grape composition and wine composition, and between wine composition and copigmentation.
Impacts
The findings have provided an understanding to how the color of young red wines relates to their phenolic composition. This major finding is important to both wine researchers and it provides a basis for improved grapegrowing and winemaking decisions.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
The studies have addressed the development of the cofactors in maturing grapes (Boulton, 2000c and Erickson, 2000) and the behavior of copigmented color during various wine treatments (Chacon-Rodriguez, 2000). The general importance of copigmentation to the color in economically significant cultivars, Sangiovese from Italy and Tempranillo and Grenache from Spain, have been presented (Boulton, 200a,b). These cultivars are experiencing a renewed interest in California and have been characterized as having poor color and color stability.
Impacts
These findings have provided the first understanding of how the color of young red wines is related to their phenolic composition. This is of major significance to both winemakers and wine researchers and it provides a basis for improved grapegrowing and winemaking decisions when color is of importance.
Publications
- Boulton, R.B. 2000. Copigmentation and the Color of Red Wines. Proceedings, International Sangiovese Conference, Firenze, Italy.
- Boulton, R.B. 2000. The Role of Copigmentation in the Extraction and Stability of Red Wine Color. Proceedings, 2nd World Wine Conference, Rioja, Spain.
- Boulton, R.B. 2000. The Variation in Skin Composition at Six Vineyard Sites. In: Proceedings 3rd International Burgundy-CaliforniaOregon Colloquium, Institut Jules Guyot, Universitaire de Dijon, France.
- Chacon-Rodriguez, L. 2000. Influence of Winemaking Practices on the Copigmented Color of Red Wines. M.S. Thesis, Univ. of Califonia, Davis.
- Erickson, A.E. 2000. Evolution of Pigments and Cofactors in the Skin of Pinot noir and Cabernet Sauvignon Grapes During Ripening and their Effect on Wine Color. M.S. Thesis, Univ. of Califonia, Davis.
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Progress 01/01/99 to 12/31/99
Outputs
The objectives of this project are to identify the major copigmentation cofactors involved in the color of red wine and determine their abundance in the major wine grape cultivars. The project will develop prediction methodologies for the level of copigmentation in wines, based on grape composition, by developing the relationships between grape composition and wine composition, and between wine composition and copigmentation. The approach to be used is to apply high performance liquid chromatography to the analysis of major wine components involved in copigmentation and assessment of the levels of copigmentation in wines using a new spectorphotometric assay developed in the lab. Measurements will be interpreted to determine common features related to the level of copigmentation in wines and to relate berry skin composition to wine composition and copigmented color
Impacts
The investigation of the effect of vineyard practices and the role of winemaking practices impact the level of copigmentation in red wines.
Publications
- No publications reported this period
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