61B-28
Effect of glass shape and storage temperature on the concentration of polyphenolic compounds in Merlot
K. RUSSELL1, J. Weiss, L. Zivanovic, and W. Morris. (1) Department of Food Science and Technology, The University of Tennessee, 2605 River Drive, Room 115, Knoxville, TN 37996
The size and shape of glasses used to serve wine has been proposed by various authors as a factor that may influence chemical composition and sensory characteristics. Nevertheless, no systematic study has been conducted that investigated the influence of glass shape on oxidative degradation of polyphenolic compounds in wine.
The objective was to determine the effect of glass geometry and storage temperature of three different glasses on concentration of polyphenolics of Merlot as a function of time.
Concentration of polyphenolics in Merlot stored in three different glasses (Flute, Bordeaux, Martini) at 22/5°C was determined at 0, 5, 30 and 1500min using HPLC-DAD analysis. A C-18 reversed-phase column (4.6x250mm, 5µm) with a gradient mobile phase (flow rate 0.6ml/min) was used. Absorbance was monitored at 280, 250, 520nm. Polyphenolic standards (catechin, epicatechin, r-coumaric acid, quercetin, vanillin, caffeic acid, gallic acid) were used to compare and quantify the time-dependent oxidative products generated.
Oxidation of polyphenolic species occurred after an onset period of 30min. Degradation was observed in shifting of lmax, reduced peak area of original component and in appearance of new peaks. The figure shows the chromatogram of a reversed-phase HPLC-DAD of Merlot oxidized in Flute (1) and Bordeaux (2) glasses after 12 hours. Standards (i.e. vanillin and quercetin) by itself showed oxidative degradation producing secondary compounds as well with a similar onset period (30min.) and were highest for the martini glass. Results of polyphenolics degradation could be correlated with available surface area indicating that mass transport processes may play a dominant role in the oxidation process. Finally, oxidation of compounds was slightly reduced at 5°C.
Glass shape influenced kinetics of oxidation of polyphenolic species which may affect sensory characteristics. Results emphasize the importance of sample container geometry in wine degustation.
Session 61B, Food Chemistry: Flavor and aroma chemistry
2:00 PM - 5:30 PM, 2002-06-17