Fact Sheet ANALYSIS

WINEMAKING Measuring wine tannins using different analytical methods /201337496692?

pt=LH_DefaultDo

main_15&var=&h

ash=item2ee0a6 6474

Introduction Wine total phenolics: This is a measure of all coloured and non-coloured phenolic The WineCloudTM provides the ability to molecules in wine that originate from grape measure tannins, phenolics and colour skin, flesh and seed. Wine total phenolics are attributes in grapes, as well as wines. The reported in absorbance units (a.u.). analysis is based on UV-Vis spectral readings and uses calibrations maintained by the AWRI. Wine total tannin: Tannins are a sub-class of Wine measurements made through the phenolics that can precipitate proteins. They WineCloudTM provide analytical data that can contribute to wine texture, particularly be directly related to measurements made astringency. When grapes are crushed, the using the Adams-Harbertson method. This tannins present in grape skin and seeds begin fact sheet aims to help you understand the to be extracted into the grape must. Those comparability of tannin, phenolics and colour from skins tend to be more easily extracted measurements made using these different than those from seeds. Once extracted, the methods. grape tannins begin to chemically rearrange, turning into wine tannins, which can be significantly different in structure from the What is being measured? original grape tannins. Wine tannin concentration is reported in g/L in epicatechin Phenolics are a chemically diverse, important equivalents. class of wine molecules that have a significant impact on the colour and taste of red wine. Wine total pigment: This is a measure of total red colour in the wine or ferment sample. For wine and ferment samples, five phenolic It is reported in absorbance units (a.u.). Total measures are available via the WineCloudTM:

Updated December 2015 Fact Sheet ANALYSIS

WINEMAKING pigment is predominantly made up of free measurement of pigments (total anthocyanins and pigmented tannins, both of anthocyanins), free (SO2 bleachable) which can also be calculated separately using anthocyanins, pigmented tannins (non- the WineCloudTM. A small amount of other bleachable/201337496692? pigments) and phenolics. Tannin pigmented compounds present in red wines content is calculated using a predictive contribute to the wine total pigment. algorithmpt=LH_DefaultDo based on the MCP method, Free anthocyanins are the highly coloured developed by the AWRI (Dambergs et al. 2012), compounds responsible for the colour of using UV-Vis measurements. red grapes. They are found in grape must, main_15&var=&h ferments and young wines, but are not Adams-Harbertson (A-H) assay very stable under wine conditions so their The Adams-Harbertson tannin assay is a contribution to wine colour decreases quite directash=item2ee0a6 adaptation of a method previously used rapidly as wine ages. Anthocyanins are for grain and ecological tannin measurement bleachable by SO2. (Hagerman and Butler 1978) and is designed to be an inexpensive and reliable6474 Pigmented tannins are stable coloured measurement of tannin and colour in wine compounds formed through the reaction The Adams-Harbertson assay utilises protein of anthocyanins with tannins during precipitation with bovine serum albumin fermentation and wine storage. Pigmented (BSA) and is used to quantify multiple classes tannins have been shown to contribute up of phenolic compounds: anthocyanins, to 90% of the colour of red wine after two tannins, pigmented polymers and non-tannin years’ storage. They are not bleachable by iron-reactive phenols. By combining protein SO2. precipitation and traditional bisulfite bleaching to distinguish monomeric How do the methods differ? anthocyanins from polymeric pigments, two classes of polymeric pigments in grapes and AWRI Method (WineCloudTM) wines can be measured: small polymeric The methyl cellulose precipitable (MCP) tannin pigments (SPP) that do not precipitate with assay is a simple and robust means of protein and large polymeric pigments (LPP) that do. The combination of SPP and LPP is measuring the total grape or wine tannin in equivalent to the SO2 resistant pigments in red grape homogenate extracts, red wine and wine (these are referred to as pigmented other aqueous solutions (Sarneckis et al. polymers by the A-H assay and as pigmented 2005). The assay is based upon methyl tannin by the AWRI method) – see Figure 1. cellulose-tannin interactions resulting in the formation of insoluble polymer tannin complexes which then precipitate. Tannin values are calculated from the difference between the absorbance values at 280 nm (A280) of solutions both with and without precipitation. This method is incorporated into the WineCloudTM, along with the

Updated December 2015 Fact Sheet ANALYSIS

WINEMAKING tannin may impact on the correlation seen between the two methods and to the difference in final tannin concentrations determined/201337496692? using the two assays. pt=LH_DefaultDo main_15&var=&h

Figure 1: Correlation between sum of large polymeric pigments (LPP) and small polymeric pigments (SPP) and ash=item2ee0a6 absorbance after SO2 bleaching

How do the results compare? 6474

Figure 2: Correlation between tannin content determined by Many research organisations have compared MCP assay and Adams-Harbertson assay the two methods (Chittenden and Smith 2011, Harbertson et al. 2003, Mercurio and Smith

2008). Results generated show that: Reference and further reading  Tannin values generated using the MCP Chittenden, R. I. and Smith, P. A. 2011. assay (utilised by the WineCloudTM) are Comparison between three different analysis highly correlated with those generated methods for tannin in New Zealand Red using the A-H assay (Figure 2). Wines. Proceedings of the American Society for  The absolute values generated by the Enology and Viticulture. WineCloudTM method are consistently Dambergs, R.G., Mercurio, M.D., Kassara, S., higher than those generated with the A-H Cozzolino, D., Smith, P.A. 2012. Rapid assay. measurement of methyl cellulose precipitable It has been reported (Mercurio and Smith tannins using ultraviolet spectroscopy with 2008) that the MCP assay removes more chemometrics – application to red wine and tannin material from the wine than the A-H inter-laboratory calibration transfer. Appl. assay and this may be explained by di- and tri- Spectrosc. 66 (6): 656-664. procyanidins and SPPs not precipitating with Hagerman, A.E. and Butler, L.G. 1978. Protein BSA. However, tannin concentration precipitation method for the quantitative differences between the MCP and A-H tannin determination of tannins. J. Agric. Food Chem. assays are not primarily caused by differences 26 (4): 809-812. in the isolation of tannin material, but rather a function of the different detection methods Harbertson, J. F. Picciotto, E.A., Adams, D.O. used. 2003. Measurement of Polymeric Pigments in Grape Berry Extracts and Wines Using a The different approaches to the quantification Protein Precipitation Assay Combined with of the pigmented tannin portion of total

Updated December 2015 Fact Sheet ANALYSIS

WINEMAKING Bisulfite Bleaching. Am. J. Enol. Vitic. 54 (4): 301-306. Mercurio, M. and Smith, P.A. 2008. Tannin /201337496692? Quantification in Red Grapes and Wine: Comparison of Polysaccharide- and Protein- Based Tannin Precipitation Techniques and pt=LH_DefaultDo Their Ability to Model Wine Astringency. J. Agric. Food Chem. 56 (14): 5528–5537. main_15&var=&h Sarneckis, C.; Dambergs, R.G.; Jones, P.; Mercurio, M.; Herderich, M.J. and Smith, P. 2006. Quantification of condensed tannins by ash=item2ee0a6 precipitation with methyl cellulose: development and validation of an optimised tool for grape and wine analysis. Aust. J. Grape 6474 Wine Res. 12(1): 39–49.

Contact

For further information, please contact:

Neil Scrimgeour

Phone 08 8313 6600 Fax 08 8313 6601

Email [email protected]

Website www.awri.com.au www.thewinecloud.com.au

Address Wine Innovation Central Building, Corner of Hartley Grove & Paratoo Rd, Urrbrae (Adelaide), SA 5064

Updated December 2015