Characterization of regional examples of New Zealand Pinot noir by means of sensory and chemical analysis

Abstract

There are four main Pinot noir wine regions in New Zealand: Central Otago, Marlborough, Martinborough and Waipara. These regions specialize in this variety as the soil, climate and other conditions are well suited to this grape. Beside being grown in these regions the wines are also marketed as regional products. Place of origin labelling implies that wines from one region will have different aroma and flavour characteristics from wines from other regions. This project determined the characteristics that best differentiate the regional styles of New Zealand Pinot noir. Marlborough Pinot noir was characterized by greater raspberry, red cherry, red fruit and red berry aromas, longer finish length and more harmonious balance. Martinborough Pinot noir was characterized by greater black cherry, chocolate, oak and spice aromas and oak tannin. Waipara Pinot noir was characterized by greater barnyard, herbal and violet aromas and in-mouth fruit density/concentration. Central Otago Pinot noir was characterized by fuller body. As regional wines were found to be stylistically different, the ability of tasters to discriminate regional wines was tested using paired comparison and sorting analysis. Tasters were not successful at discriminating regional wine examples using these techniques. This may be due to conceptual models that are not representative of the regional wines.

In order to determine the possible causes of these regional differences the chemical composition of the wines was also investigated. Three HS-SPME-GC-MS methods were developed specifically for Pinot noir wine to measure 34 different volatile organic compounds. One method measured compounds found at higher concentrations, namely esters and alcohols, the second method measured volatile fatty acids and the third measured trace compounds present at very low concentrations.

With the two sets of information, sensory and chemical, it was possible to find relationships using canonical correlation analysis. Results indicated four aroma compounds of particular importance: ethyl octanoate, ethyl decanoate, 2-phenyl ethanol and benzaldehyde. Addition/omission tests were used to determine the influence of each compound on Pinot noir aroma. The compounds were added in combination and at varying concentrations to a wine matrix, which consisted of a commerical Pinot noir that contained low levels of the compounds of interest. In 8 of 10 triangle tests panellists were able to successfully identify samples with different concentrations of the components.

Panellists also used descriptive analysis to determine the influence of these compounds. From the descriptive analysis results it was found the 2-phenyl ethanol influenced the perception of violet aroma, ethyl octanoate influenced red cherry aroma and the combination of ethyl octanoate and ethyl decanoate influenced black cherry aroma. The measurement of the effect of these aroma compounds is a first step to understanding some factors of regional style since red cherry, black cherry and violets were descriptors that characterize the regional styles of New Zealand Pinot noir.