When perusing the calendar of national and global awareness days, there was one we simply couldn’t ignore: National Wine Day. Observed annually in the United States, it even has a sister holiday in February, National Drink Wine Day. To mark the occasion, our BioLabTests scientists looked at the science behind one of our favourite alcoholic beverages (note: no alcohol was consumed during this research).

The concept of “terroir”

Wine experts will describe the various factors that contribute to the taste of a wine as “terroir”, a collection of the regionally distinctive characteristics of wine that have an effect on its composition. It is the environmental factors such as soil types, climate, topography and human management that are said to contribute to its character.

The concept of terroir originated in France due to the observable differences in wines from different regions, vineyards and even within of the same vineyard. Microbiologists have added to the picture by studying the microbiology of the wine-making process in fine detail. It appears wine terroir is largely dependent on the collection and diversity of microorganisms related to the grape and fermentation process, the so-called microbiome, which contributes to wine quality and style characteristics.

The impact of microbial activity

The grapevine phyllosphere, the part of the plant completely exposed to air that acts as habitat for microorganisms like yeasts, fungi and bacteria, is able to significantly modify the grapevine’s health, growth and grape production.

These microbes can come from the vineyard soil, air precipitation or be transported by animals, and when they are transferred to the wine must, which is freshly pressed grape juice, they have a substantial effect on the composition, quality and flavour. For instance, the presence of fermentative yeasts, such as Saccharomyces cerevisiae, and lactic acid bacteria modify the flavour and aroma of the wine.

Microbial geography

A recent study in Australia aimed to describe the importance of microbial geography on wine production, considering how the microbes’ interaction with environmental factors affect the distinctiveness of a wine.

As microorganisms adapt to their surroundings, different microbial populations are present in different regions, influencing how microbial ecology develops and diversifies and directly affecting the final wine’s quality and style. For example, climate is one of the most important affecting environmental factors; while cooler climates are better for producing light and delicate wines, heavy and rich ones are better grown in warmer climates, shaping the variety of microorganisms present in a specific region.

However, human management practices can be included in the process to modify the microbiome of the wine, maximising microbial diversity and being able to dictate the flavour of the wine by techniques like cold soaking, used to favour wine colour by increasing yeast populations.

So when opening your next bottle of wine, tune into these different flavours and raise your glass to all the hardworking microorganisms and winegrowers that made it possible.
#NationalWineDay