Yeast doesn’t just make alcohol — it makes flavour.

Yeast is often treated like just the engine of fermentation. But what it does in the wash shapes everything that follows.

From fruity esters to spicy alcohols… from creamy texture to savoury depth — fermentation is where flavour begins to take shape.

Here’s what yeast contributes during fermentation:
🍐 Esters – fruity and floral notes like pear, banana, and apple. These come from reactions between alcohols and acids inside the fermenter.
🔥 Fusel alcohols – heavier, spicier alcohols that add oily weight and structure. Think warmth, body, and (when balanced) depth.
🧈 Fatty acids – waxy or creamy on their own, but essential for creating fruity esters. They also affect mouthfeel.
🌿 Sulphur compounds – tricky to manage, but capable of bringing meaty, savoury layers. Some evolve into brighter, fruitier esters during distillation and ageing.
🌾 Aldehydes – grassy or nutty notes in young spirit, and key building blocks for acids and esters later in ageing.
🧪 Ethanol – not just alcohol, but the solvent that extracts oak flavour during maturation. It carries aroma compounds, shapes mouthfeel, and helps everything else shine.

Yeast strain, fermentation time, temperature, nutrients — all of it influences the final profile before the spirit even reaches the still.

📌 Infographic attached – Check it out

Over the next few posts, I’ll break these down one by one — starting with esters and the fruity backbone they give to so many spirits.

What’s your take — is fermentation the unsung hero of flavour? Or does the cask still deserve all the glory?