Since objective measures of appellations are needed for wine, California Vitis vinifera Var. Chardonnay wines (n = 48) were surveyed for several aroma compounds including esters, norisoprenoids, and terpenes. For the first time concentrations of volatile fragrances were directly correlated with descriptive analysis scores that statistical analysis of the sensory data showed were associated with regional uniqueness and distinctness. Sensory scores for 10 terms used by industry quality experts to describe wines from four regions were compared to the concentrations of over 30 wine chemical compounds. Frequency of use of individual grape-based aroma terms were significantly correlated (p < 0.05) with linalool, 1,1,6-trimethyldihydronaphthalene, 3-methylbutyl acetate, ethyl 2-hydroxypropanoate, and 2-phenylethanol. Linalool concentrations were also correlated with α-terpineol. Also, 4-terpineol, geraniol, nerol, and linalool oxide (furan) were found in Chardonnay wines from all of the regions of California. Keywords: Aroma; Chardonnay; descriptive analysis; flavorants; norisoprenoids; sensory analysis; terpenoids; terroir; Vitis vinifera; wine
Since producer based sensory analysis of wine appellations remains in widespread use worldwide by wineries, modern sensory methods were developed for industry judge panels. U.S. appellations were studied using modern sensory analysis processes which accommodated the industry professionals’ biases for perceived quality and provincial sensory language. A panel was assembled comprised of wine industry quality experts (n = 26). First, judge quality biases were determined using a multi‐wine preference‐testing method (n = 48) in which judges freely record their aroma terms. Subsequently QDA° type strategies were used to create the sensory language from analysis of 1100 wine X judge interactions in which free use of terms was used to describe the wines. Next, an experiment analyzed the wines using a new descriptive analysis scorecard which contained the ten most frequently used terms; and scores were computed from the number of times terms were selected by the judges (frequency of use). Groups of sixteen wines, for which the judges had no large negative bias, from the Carneras American Viticutural Areas (AVA), were compared to those from California wine growing regions (Central Coast, Napa and Sonoma). Replicate trials showed Carneras AVA and Central Coast wines clustered in the principal components (PCA) analysis of the sensory data. The detection of regional typicalness by professionals: (1) was linked to their perceived quality bias, (2) was easily detected in high quality wines linked to grape attributes more than to winemaking attributes, and (3) was not possible when judges had determined that perceived wine quality was low. ANOVA and polar spider plot analysis of the clusters indicated that the important aroma attributes of Carneros wines included Citrus and Green Apples/Pears. Lastly, the sensory analysis data was compared to chemical analysis of terpenes for several wines (n = 22). Chardonnay terpene (linalool) concentrations were highly correlated (p < 0.01) with the attribute scores for Citrus which was important in the PCA analysis of the sensory data. These sensory processes offer a descriptive analysis process that accommodates the wine industry professional. The method also offers several advantages over flavor profiling methods including the reduction of the potentially confounding problems of “quality” and “standard terms” among industry professionals as well as speed and correlation with chemical analyses.
The poor precision of the Adams-Harbertson wine tannin assay which was proposed for commercial winemaking, thereby creating the real possibility of quality control problems, is documented. The method is a version of the Hagerman and Butler protein precipitation-based tannin method. An extensive invalidation of the assay results with luxury wine data shows that the assay cannot distinguish bottled wine with reasonable accuracy. Five laboratories used Adams-Harbertson to assay 9 replicates each, of 3 bottled wines (n 135) found in California supermarkets, with tannin concentrations of nominally 500 and 1000 ppm by high-performance liquid chromatography (HPLC). Reliability exceeded the 5 industry requirement by nominally 5 times (z-score based on 5 distribution). Coefficient of variation was 27, making the standard deviation range 54 for Pinot Noir, 34 for Merlot, and 44 for Cabernet Sauvignon. Validity exceeded the 100 requirement. Intralaboratory validity recovery was 5563. Interwinery validity was 71178 of the mean for Pinot Noir, 81144 for Merlot, and 83164 for Cabernet Sauvignon. Range as a function of the mean was 89 for Pinot Noir, 55 for Merlot, and 67 for Cabernet Sauvignon. Expect intermethod validity to be nominally 50, i.e., percent recovery to HPLC. These statistically significant errors were predicted by the literature. First-order error is related to the tannin-protein equilibrium constant (Ka), as suggested by the original author, Hagerman, and the protein equivalence point error as suggested by Silber. This does not obviate second-order errors for tannin-protein analytical chemistry. Winemakers using the measurements risk making wines that are relatively more tannic than the measurements report.
The poor interoperability of anthocyanin glycosides measurements by two pH differential methods is documented. Adams-Harbertson, which was proposed for commercial winemaking, was compared to AOAC Official Method 2005.02 for wine. California bottled wines (Pinot Noir, Merlot, and Cabernet Sauvignon) were assayed in a collaborative study (n=105), which found mean precision of Adams-Harbertson winery versus reference measurements to be 77 +/- 20%. Maximum error is expected to be 48% for Pinot Noir, 42% for Merlot, and 34% for Cabernet Sauvignon from reproducibility RSD. Range of measurements was actually 30 to 91% for Pinot Noir. An interoperability study (n=30) found Adams-Harbertson produces measurements that are nominally 150% of the AOAC pH differential method. Large analytical chemistry differences are: AOAC method uses Beer-Lambert equation and measures absorbance at pH 1.0 and 4.5, proposed a priori by Flueki and Francis; whereas Adams-Harbertson uses "universal" standard curve and measures absorbance ad hoc at pH 1.8 and 4.9 to reduce the effects of so-called co-pigmentation. Errors relative to AOAC are produced by Adams-Harbertson standard curve over Beer-Lambert and pH 1.8 over pH 1.0. The study recommends using AOAC Official Method 2005.02 for analysis of wine anthocyanin glycosides.
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