Michigan Grape & Wine Industry Council Annual Report 2012 Title: Determining pigment co-factor content in commercial wine grapes and effect of micro-oxidation in Michigan Wines Principal Investigator: Kris A. Berglund, Ph.D., Michigan State University,BBIM Suite 1031E, 3815 Technology Blvd., Lansing, MI 48910 Goals and Objectives This project aims to measure the concentrations of color-stabilizing co-pigmentation factors in several Michigan grape varieties. This information is combined with anthocyanin (pigment) concentration data, to provide winemakers better control over color and stability in Michigan red wines. Objectives: 1. Develop a procedure to measure the concentration of polyphenolic co-pigmentation factors in grape skins, seeds, and pulp 2. Measure the concentrations of several polyphenolic co-pigmentation factors in several Michigan wine grape varieties 3. Measure the concentrations of anthocyanins in several Michigan wine grape varieties 4. Assess the effect of micro-oxygenation on color expression in Michigan red wines RESULTS & CONCLUSIONS Objective 1: Develop a procedure to measure the concentration of polyphenolic co-pigmentation factors in grape skins, seeds, and pulp. A procedure to extract polyphenolic and anthocyanin molecules from seeds, skins, and pulp from grapes was developed and successfully applied to 20 Michigan grape varieties. A procedure was developed for High Performance Liquid Chromatography (HPLC) to measure the concentration of 10 co-pigmentation factors. Currently, 3 factors have been successfully quantified, and work is ongoing to improve the method and identify the other 7. A typical chromatogram can be seen in figure 1. Work is currently underway to develop a pre-treatment for the skin and seed extracts which will make the separation both easier and less costly to perform. Objective 2: Measure the concentrations of several polyphenolic co-pigmentation factors in several Michigan wine grape varieties. 3 major polyphenol groups were successfully identified and quantified in 10 white and 10 red grape varieties. These results are shown in table 1 and table 2. Results include polyphenol content in both skins and seeds. Work on this objective is ongoing.
Objective 3: Measure the concentrations of anthocyanins in several Michigan wine grape varieties. A method was developed for HPLC to quantify anthocyanin concentrations in Michigan red grape varieties. Anthocyanins were qualitatively separated using this method; data will be quantified upon proper calibration using known standards. Observation and UV-VIS absorption spectra correlate well with these results. A collaboration with Prof. Dana Spence in the Department of Chemistry at MSU has been developed to assist with this objective and a nocost extension has been requested to finish this work. Objective 4: Assess the effect of micro-oxygenation on color expression in Michigan red wines. This objective has been completed. Two wineries provided wine samples throughout the microoxygenation treatment. UV-VIS spectra were taken over the entire visible spectrum. Example results can be seen in Figure 3. These data will be further analyzed using the new collaboration listed under 3 above during the no-cost extension. 3. Project Period Project period: January 1, 2011 to December 31, 2012 4. Work accomplished during the period, including methods. Sample Preparation. Grape samples were received in bulk from participating wineries and stored at -78 C until analysis. Prior to analysis, samples were thawed and drained. Seeds, skin, and pulp were separated by hand. Seeds and skins were dried in an oven at 35 C, then extracted in a 50% ethanol/methanol solution. Pulp samples were acquired by hand pressing to extract juice. All samples were filtered through a.22 micron syringe filter prior to injection. HPLC Analysis. A method was developed for separation of anthocyanins and polyphenols. Exact operating parameters for the HPLC are available upon request. A typical chromatogram can be seen below. Figure 1 - Typical chromatogram of polyphenolic content, detected at 280 nm Comparison between grape varieties. Gallic acid, Hydroxybenzoic acid, and total catechins (catechin + epicatechin) were measured for ten red and ten white grape varieties. The results were normalized and compared, as seen in Figure 2 below.
1.2 Normalized Co-factor Concentrations Normalized Concentration 1 0.8 0.6 0.4 0.2 0 Foch - St. Julian Foch - St. Julian Rougeon - St. Julian Merlot - St. Julian Merlot - St. Julian Cab Franc - Black Star Farms Cab Franc - Fenn Valley DeChanae - St. Julian Concord - St. Julian Unknown - St. Julian Catawba - St. Julian Seyval - St. Julian Seyval - St. Julian Seyval - Oxley Chardonnay - St. Julian Chardonnay - St. Julian Chardonnay - Fenn Valley Chardonnel - St. Julian Vidal - St. Julian Niagara - St. Julian Pinot Grigio - Fenn Valley Pinot Gris - St. Julian Pinot Gris - St. Julian Riesling - Tramonnette - St. Julian Gallic Hydroxybenzoic Total Catechins Figure 2 - Normalized concentrations of 3 major polyphenol co-pigmentation factors: Gallic acid, Hydroxybenzoic acid, and Catechin/Epicatechin The data show, as seen in Figure 2, that there is wide variation in co-pigmentation factors between grape varieties. Certain varieties, such as DeChanae and Chardonnel, show promise for blending due to their high cofactor concentrations. The data may also offer insight to varieties which suffer from color stability problems; many of these varieties have low concentrations of co-pigmentation factors. UV-Visible Absorption. Five different wine varieties were analyzed throughout the microoxygenation treatment. UV-Visible absorption spectra were taken from 280 to 890 nm for each sample. For each week of trials, a control sample of untreated wine was also tested. The spectra were then compared to assess the change in absorption caused by the micro-oxygenation treatment. The spectrophotometer used is miniaturized and potentially could be deployed in the field.
0.2 Change in Absorbance after 4 Weeks 0.1 Change in Absorbance (AU) 0-0.1-0.2 0 200 400 600 800 1000 MOX Treated Sample Control Sample -0.3-0.4 Wavelength (nm) Figure 3 - Effect of Micro-Oxygenation on Color in Pinot Noir (Chateau Chantal 2011) Figure 3 shows the results of a four-week micro-oxygenation treatment on a typical Pinot Noir wine. The untreated wine decreased in absorbance over the visible range of interest (400-700 nm), while the micro-oxygenated wine gained in absorbance. The data also show a shift in shape of the spectra, which indicate a change in hue visible in the wine. Overall, the data show that the micro-oxygenation treatment stabilized color compounds (preventing color loss), and enhanced their expression. Through this project we have gained the ability to monitor color attributes of wines via UV-VIS spectroscopy in real time. 5. Communications Activities, Accomplishments, and Impacts. i. Dave Miller presented on co-pigmentation at ASEV meeting, July 2012 ii) Paul Jenkins presented a poster on Micro-oxygenation at ASEV meeting, July 2012 iii) Communications with participating wineries is ongoing. 6. Industrial interactions An important element to the project is to ensure the results are of an applied nature. To this end, several participants were recruited to collect field samples. They are Jess Broadhurst and Nancie Corum-Oxley at St. Julian; Todd Robbins and Eric Heavlin at Fenn Valley; and Dave Miller at White Pine Winery.
ABSTRACT Color is a very important characteristic of red wine, and therefore it is important for winemakers to be able to control both the final color and the color stability of their wines. The color of red wine is due to a complex system of anthocyanin pigments and polyphenolic co-pigmentation factors. The relative concentrations of each type of anthocyanin and co-pigment factor control the final expression of color in the wine. This study aims to help Michigan wine makers better predict and control the color properties in their wines by measuring the anthocyanin and copigmentation factor content in the seeds, skins, and pulp of several Michigan grape varieties. Initial results show wide variation between grape varieties, and suggest that further research would be beneficial.