Adams-Harbertson protein precipitation-based wine tannin method found invalid

Area of Science:

• Analytical Chemistry
• Food Science
• Enology

Background:

• The Adams-Harbertson assay is a protein precipitation method for wine tannin analysis.
• Accurate tannin measurement is crucial for wine quality control and commercial winemaking.

Purpose of the Study:

• To document the poor precision and validity of the Adams-Harbertson wine tannin assay.
• To assess the assay's suitability for commercial winemaking quality control.

Main Methods:

• Five laboratories assayed three bottled wines (Pinot Noir, Merlot, Cabernet Sauvignon) using the Adams-Harbertson method.
• Results were compared against tannin concentrations determined by high-performance liquid chromatography (HPLC).
• Statistical analysis included reliability, coefficient of variation, and validity assessments.

Main Results:

• The assay demonstrated poor reliability, exceeding industry requirements by five times.
• Coefficients of variation were high (+/-27%), with significant standard deviation ranges for different wine varietals.
• Validity assessments showed substantial deviations from expected values, with interlaboratory and interwinery results varying widely.

Conclusions:

• The Adams-Harbertson assay is not sufficiently precise or valid for accurate tannin measurement in bottled wines.
• The assay's limitations pose a risk to wine quality control, potentially leading winemakers to misjudge tannin levels.
• Further research into tannin-protein analytical chemistry is needed to address inherent errors.