Laura Weissberg,* Greg Hirson, and Antonio Ferreira
*Tonnellerie O, 531 Stone Road, Benicia, CA 94510 (lweissberg@tonnellerieo.com)

Inconsistency in fire-toasted barrels has been problematic for winemakers throughout winemaking history. Variance in toast profiles from a single cooper can cause unanticipated variance in resulting flavor profiles. To address the cooper’s dilemma, near infrared (NIR) spectroscopy was investigated for use as a tool after toasting to measure the magnitude of heat treatment for common fire-toast profiles. NIR spectroscopy is frequently used in the wood and paper industries as a viable, rapid, and inexpensive means to quantify wood constituents and aroma and flavor precursors: cellulose, hemicellulose, lignin, and extractives. Spectra were collected on different convection-baked oak profiles: 225-L American oak barrels with 27-mm staves and 225-L French oak barrels with 22-mm or 27-mm staves. Principal component analysis (PCA) of the NIR spectra revealed distinguishing spectral features for convection-baked treatments and fire-toasts of blonde, medium, medium plus, and heavy. The first two principal components explained over 95% of the variance across toast profiles. Using PCA, barrel-to-barrel variation was quantifiable and was greatest for moderate-toast levels. Differences in raw wood composition and variance in production were likely contributors to spectral differences within toast levels. Analysis of toasting magnitude for traditionally toasted barrels by NIR was deemed feasible and reliable as a quality assurance method to assure winemakers of toasting uniformity.

Funding Support: Cork Supply USA