Mitchell Davey, Danielle Fox, and James Harbertson*
*Washington State University, 2710 Crimson Way, Richland, WA, 99354-1671 (jfharbertson@wsu.edu)

A commercial freeze-dryer was used to emulate the effects of freeze-killed leaf material on Cabernet Sauvignon wines in 2023. Fresh leaves were collected from a vineyard in Sunnyside, WA one month prior to harvest, and freeze-killed leaves (FK) were collected at harvest. The fresh leaves were subjected to freeze-drying (FD). The FK and FD leaves were added directly to the must prior to fermentation at two rates (0.9 and 3.6 g/kg must) including a control (0 g/kg must). Basic wine chemistry was unaffected by the additions. Untargeted solid-phase microextraction gas chromatography-mass spectrometry was used to identify major aroma compounds present. Tentatively identified compounds were evaluated statistically. Twenty-three compounds were found to vary significantly based on the treatments. Alcohols were significantly reduced by both leaf treatments. Terpenoids and norisoprenoids significantly increased with increased leaf dosages. A previously-suggested frost taint marker, 6-methyl-5-hepten-2-ol, which smells like coriander was only found in the FK-treated wines. Esters significantly increased in both treatments, consistent with dosage. Phenolics were measured in the wines using the Adams-Harbertson assay. Counter to previous results, wines made with both FK and FD leaves had significantly more phenolics and anthocyanins were unaffected. With the exception of the single frost taint marker, the FD treatments emulated the FK-treated wines.

Funding Support: Washington Wine Commission