Ling Huang, Jingwen Li, Yanping Qian, Patty Skinkis, and Michael Qian*
*Oregon State University, 3051 NW Campus Way, Corvallis, OR 97331 (michael.qian@oregonstate.edu)

Cluster thinning is a traditional practice used in premium wine production to reduce yield, as it is thought to improve fruit quality. The impact of cluster thinning levels on Pinot noir wine quality was studied in this work. Total monomeric anthocyanin, total phenolic content, polyphenols, and volatile profile of Pinot noir wines from Oregon commercial wineries were analyzed over several vintages. Crop level was adjusted us- ing cluster thinning at the lag-phase of berry development using a cluster number per shoot regime or ton per hectare treatments, and many vineyards included a full-crop control (no thinning). Total monomeric anthocyanin was determined with a spectro- photometer based on the absorbance change of anthocyanin at different pH. Total phenolic content was analyzed using the Folin-Ciocalteu colorimetric method. Wine polyphenols were analyzed with high-performance liquid chromatography. Volatile aroma profile of wine was analyzed with solid-phase microextraction gas chromatography-mass spectrometry (SPME GC-MS) headspace-GC-Flame ionization detector and SPME-GC-PFPD according to properties of aroma compounds. Isotope internal standards were used to build standard calibration curves. In general, cluster thinning affected the monomeric anthocyanin, total phenolic content, and anthocyanin levels in wines compared to the no-thinning treatment. Volatile compound concentrations also were influenced by cluster thinning, but the effect was inconsistent among vine- yards and vintages.

Funding Support: USDA-ARS