Winemaking under the electron microscope

While most of us enjoy a glass of wine or three, we are blissfully unaware of the science of winemaking or oenology. While winemakers or vintners themselves may not be scientists as we know them, there is no doubt they have an in-depth understanding of their craft, and a whole lot of patience.

According to data released by the Australian Bureau of Statistics, our wine consumption has been relatively consistent over the last 15 years. While wine is our second favourite alcoholic beverage behind beer (based on pure alcohol volume), wine accounts for 38.3% of the alcohol consumed, trailing beer by less than 1%. Beer consumption, however, has been in steady decline since the heady days of mid-70s. In fact, the steady decline in beer consumption has resulted in Australia’s lowest alcohol consumption in 50 years.

The growing of grapes specifically for winemaking or viniculture is obviously a key part of the winemaking process. While winemakers no doubt have a good understanding of what makes their crops grow the best, it is unlikely they have ever used a scanning electron microscope (SEM) to look at their valuable produce.

Consequently, TESCAN, a leading manufacturer of SEMs based in the Czech Republic, and the National Wine Centre collaborated and undertook such a study looking at grape vines and winemaking at high magnifications. TESCAN is located in the city of Brno, in the region often referred to as the cradle of electron microscopy in Europe. Brno is also the capital of Moravia, responsible for 95% of the national wine production. The samples used in this study were provided by the Department of Viticulture and Viniculture at Mendel University, also located in Brno.

The resulting electron micrographs provide a highly detailed view of structures relating to winemaking, revealing features that are largely invisible to winemakers and wine lovers alike. The images were blown up and put on display last year in a public exhibition in the cellars of Valtice Castle, home of the National Wine Centre and part of a UNESCO World Heritage Site.

Detail of a stoma — a respiration pore on the bottom side of a grape leaf. Used for nutrient exchange (CO₂ and O₂ in particular) between the plant and surroundings.

Starch grains (proteins) deposited in the vascular tissues.

Brettanomyces yeast cells that are responsible for the ‘brett’ character of wines.

Potassium bitartrate of potassium hydrogen tartrate crystal with yeast cells. Its crystallisation produces turbidity in the form of fine white or yellowish sediment. While it does not affect the taste or smell of the wine, it has a negative effect on the aesthetics of the wine.

Wine clarification filter used to purify wine before bottling with pores in the range 0.45 to 1.2 µm. These membrane filters are used to remove certain yeast cells and bacteria.

Pavel Krška, Director of the National Wine Centre, commented, “As far as we know, this exhibition is the first of its type and the feedback from visitors has been extremely positive. They are in awe of the images and visitors appreciate the fact that they are being given access to highly scientific content presented in such a way that it appeals to wine aficionados and the broader community.”

Images by TESCAN.