Published in Analytical Chemistry Research, their study investigated how the same grape variety - Pinot Noir - creates different wines with different profiles. They say the variety of processing techniques used - and chemicals added during production - are responsible for this.
Alongside the alcohol content, labels should contain information on sugar, organic acid, and mineral content, they add.
The researchers from University of Helsinki took eight bottles of red wine, all made with Pinot Noir grapes. The wines came from the US, New Zealand, France, and Chile.
According to legislation, 75-85% of the grapes must be from the same district.
Wine portions were each analysed six times, with two replicates. Bottles were stored at 4°c and protected from sunlight and air.
The winemaking processes used were natural fermentation, fermentation (without details), biodynamic fermentation (from organic grapes), micro-oxygenation, yeast fermentation, wild fermentation and cold fermentation.
“The study describes profiling of eight Pinot Noir red wines,” wrote Heli Sirén, one of the authors, in the study.
“The purpose was to detect differences between them by quantifying both organic and inorganic compounds in the wines that were bottled in the years of 2007–2009. They were selected as representatives of “good vintage” of the young red wines, which have differences in the production. According to our knowledge, similar studies have not been carried out previously.”
Alcohol content and acidity
Winemakers can add sugars during processing. Researchers were able to determine what had been added by looking at the acids - organic compounds - in the wine, and also tell if sulphur dioxide had been added to stop the wine from oxidising.
One of the US wines used micro-oxygenation - one of the newer processes used by the wine industry - which was shown to reduce levels of anthocyanin (grape pigment). These wines had the highest sugar levels, because sugars were not broken down during manufacturing. Consequently, they did not have added sugar.
The New Zealand wine, processed by malolactic fermentation and yeast addition, had the highest amounts of acetic, malic and lactic acids, as well as acetaldehyde. This made it the most acidic and alcoholic of the eight samples.
“The study showed that the profiles of Pinot Noir wines vary with composition of organic and inorganic compounds,” continued Sirén. “The Pinot Noir red wines that were produced in normal winemaking contained higher concentrations of organics than those made with new process technologies. Micro-oxygenation seemed to reduce the quantities of anthocyanins.”
Source: Analytical Chemistry Research 3 (2015). doi:10.1016/j.ancr.2014.10.002
Title: “Evaluation of organic and inorganic compounds levels of red wines processed from Pinot Noir grapes”
H. Sirén; K. Sirén; J. Sirén.