At first glance, a vineyard might seem like a peaceful stretch of vines basking in the sun. But beneath the surface – on the leaves, the grape skins, and even in the juice before fermentation – there’s a bustling community of microscopic life that plays a crucial role in shaping the quality and character of wine.
Recent groundbreaking research from Stellenbosch University and the University of the Western Cape has shed light on the fascinating microbial diversity found on two of South Africa’s most beloved grape varieties: Chardonnay and Pinot Noir. This study focused on vineyards in the Elgin and Hemel-en-Aarde wine districts, exploring how fungi and bacteria colonise grapevine leaves (the phyllosphere), grape berries (the carposphere), and the grape must (the freshly crushed grape juice before fermentation).
Why Microbes Matter in Winemaking
Microorganisms like yeasts, bacteria and fungi aren’t just passive passengers on grapevines. They influence grape health, growth and, ultimately, the flavour and aroma profiles of the wine. Indigenous microbes present on grape berries kickstart spontaneous fermentations, contributing unique and complex characteristics that are impossible to replicate with commercial yeast strains alone.
What Did the Study Find?
- Key Players: The most abundant bacteria found on leaves and berries belonged to the genus Pseudomonas, while the dominant fungi were from the genus Filobasidium.
- Microbial Differences by Sample Type: There were clear differences in microbial communities between leaves, berries and grape must, but, surprisingly, the type of grape (Chardonnay vs. Pinot Noir) and vineyard location didn’t significantly change which microbes were present.
- Influence of Grape Skin: The integrity and characteristics of the grape skin, such as thickness and micro-fissures, appear to influence microbial diversity. Thin-skinned varieties like Chardonnay tend to harbour more diverse microbial populations because their skins allow easier access to nutrients.
- Stable Fungal Communities: Fungal diversity remained relatively consistent across different stages of grape development, suggesting a stable fungal ecosystem on the grapevine.
What This Means for Wine Lovers and Winemakers
Understanding the microbial landscape of vineyards offers exciting opportunities to enhance wine quality naturally. By appreciating how microbes interact with grapevines, winemakers can:
- Harness indigenous microbial communities to produce wines with distinctive regional character.
- Develop vineyard management practices that support beneficial microbes, potentially reducing reliance on chemical treatments.
- Tailor fermentation strategies to preserve or highlight unique microbial contributions, especially in premium and sparkling wines like South Africa’s famous Méthode Cap Classique.
The South African Context
Chardonnay and Pinot Noir together make up nearly 9% of South Africa’s wine grape production, with many vineyards dedicated to crafting world-class still and sparkling wines. This study fills an important knowledge gap by profiling the microbiomes of these cultivars in South Africa’s cool-climate regions, helping local producers maintain and elevate their wine quality.
In Conclusion
Next time you savour a glass of South African Chardonnay or Pinot Noir, remember the invisible microbial allies that helped shape its flavour. This research not only deepens our understanding of vineyard ecosystems but also opens doors to innovative, sustainable winemaking that celebrates the natural complexity of the grapevine microbiome.
Stay tuned for more insights into how science is unlocking the secrets of terroir, one microbe at a time.