22 July 2014

Which wine to take home? Sensory analyses of wine regions provides a clue


This blog post was written by postgraduate student Yunxuan Qin in the course, Research Methods in Ecology (Ecol608). Yunxuan revisits a Lincoln University research area that looks at how the region of origin affects wine traits from 2013.

Walking through wine aisles in a supermarket, different brands of wines fill the shelves. Besides all the appealing labels, there must be some inherent differences hidden within the bottles. Unless opened and tasted, the characteristics of the wine remain a secret. However, there is always a clue on the label, indicating where the grapevines were planted and the wine region of origin. Indeed, the expression of regionality is an important part of the philosophy of winemakers in all parts of the world.

Wine shelves in a French supermarket. Photo by christine592, CC BY-ND 2.0. 
That philosophy about regionality is based on a concept, "terroir", which has long been recognized but is difficult to interpret. Terroir itself includes many factors, such as climate, soil type, and topography. The common understanding of terroir is "a sense of place" that wines from specific geographic locations can be perceived as different. According to Patrick Iland's, past Senior Lecturer at The University of Adelaide, book The Grapevine: from the science to the practice of growing vines for wine, terroir modifies the flavor shape of wines from different sites within a region, sub-region and even within a vineyard block. Sometimes, the soil characteristics became the predominant factor impacting on vine growth, berry composition and wine style and quality, as indicated in the figure below.
A "vine to wine" web showing vine, berry and wine characteristics from terra rossa and deep black cracking clay soils. Adopted from The Grapevine: from the science to the practice of growing vines for wine, page 287. 
If we knew the differences in wine characteristics between regions, we could easily make the purchase decision by personal wine tasting preferences, instead of standing in front of wine shelves making a hopeful selection.

Another question is how to measure wine characteristics between regions? Wine characteristics are measured by sensory attributes, which are difficult to measure. Indeed, everything related to human sensation is hard to interpret. Variables such as personal odor threshold, physiological status (with perceived astringency by saliva as an example), psychological status (with emotional attributes and wine perception as an example) and descriptive vocabulary are examples. Thus, these variables are the reason why human perception of wines will vary from person to person, which makes it difficult and impossible to establish a standardized wine tasting note for every individual wine.

A recent study from Elizabeth Tomasino and co-workers aimed at measuring the differences in Pinot noir wine according to their sensory attributes (e.g. aroma, in-mouth flavor, mouthfeel) from four regions in New Zealand. Pinot noir, one of the noblest red grape varieties, is now the most widely planted red grape variety in New Zealand with these wines frequently compared to those from Burgundy. Several degrees of latitude were covered, including Central Otago, Marlborough, Martinborough, and Waipara. These regions were studied as Pinot noir is a locally important wine variety in these places.

How did they determine wine characteristics according to different regions? Elizabeth and co-workers did a preliminary tasting by six panelists who afterwards, listed wine aroma and palate descriptors for each of the wines. Combined with previous sensory work, a final list came out, including twenty-five attributes (fifteen for aroma, four for in-mouth flavor, six for mouth-feel). The formal tasting then conducted by asking twenty-one panelists to rank the intensity of each of the twenty-five attribute.

As customers, which Pinot noir wine shall we choose from the four regions? According to the results from Elizabeth and co-workers, you can have following options. If you want something red and fruity, you'd better choose Marlborough Pinot noir wine. It was characterized by greater raspberry and red cherry aromas, a red fruit in-mouth flavor, and longer finish length with a more harmonious balance. If you prefer a note of dark fruits and oak, Martinborough Pinot noir wine should be your first choice. Greater black cherry, oak, and spice aromas and oak tannin mouthfeel describe this wine. If you desire a herbal note in your "glass of wine", then the Waipara Pinot noir will be recommended for greater barnyard with violet aromas and a decent in-mouth fruit density/concentration. If you want something neutral, choosing Central Otago Pinot noir wine would be wise. It was the intermediate one and had fuller body.

The sensory table, filled with many of the aromas wine may possess.
Photo by H. C., CC BY-NC 2.0CC BY-NC 2.0
Based on the knowledge of wine characteristics upon corresponding regions and your own preference, followed by checking the region on the label, it won't be hard to make a decision. Indeed, you already establish an expectation before opening the bottle. Another choice is doing a blind selection, and having fun to discovery the secret hidden in the bottle.

Nevertheless, nature plays a magical role on wine sensory profiles/styles according to different regions. We often address "terroir" to roughly explain the cause, but which factor of the terrior contributes the most to the differentiation remains to be discovered by scientists. Actually, one of my colleague is currently working on it (check the wine research topics in Lincoln University).

How reliable is Elizabeth research results? You have to find out by yourself. Enjoy your wine. Cheers!

Reference
Elizabeth Tomasino, Roland Harrison, Richard Sedcole, and Andy Frost,(2013) Regional differentiation of New Zealand Pinot noir wine by wine professionals using canonical variate analysis. American Journal of Enology and Viticulture.64, 357–363.

Iland, P. and Promotions, P.I.W., (2011) The grapevine: from the science to the practice of growing vines for wine. Patrick Iland Wine Promotions.



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