Fermenting with stone – Novum’s experimental approach to winemaking for Chardonnay
The inspiration
Our Chardonnay vineyard in the central Wairau Plains of Marlborough is full of old greywacke stones, which came from a riverbed many hundreds of years ago. This greywacke rock makes up most of the soil matrix (with brown soil contributing less than 10% of the soil profile).
As these stones have eroded over time, they have slowly released minerals into the soil, with our old vines having gradually absorbed them. It is these minerals that give our Chardonnay fruit its extraordinary oyster shell, citrus and mineral flavour profile and tight acid structure that we love so much. In winemaking language, we call this ‘a sense of place’.
Last summer, after walking through the vineyard, Will wondered what would happen if we added the stones to our Chardonnay during ferment. He saw the possibility for the stones to have many positive impacts on the wine. Much of his earlier years of wine training focused on biodynamics, which talks in part about the movement of energy. Could the energy from the stones move into our wine and add that elusive 1% improvement to our vineyard’s signature flavour profile?
Our first experiment using stone started with the 2024 vintage juice: we removed the barrel head from 5% of the barrels and placed one large stone selected from the Wairau River inside each barrel before replacing the head again and filling the barrel with juice ready for wild fermentation.
The transfer of energy
Where does this ‘energy’ come from? There is a biodynamics principle that says energy is never lost, only transferred from one form to another. Hence it is possible for inanimate objects such as stones to absorb energy from the environment around them. In our case, these stones originate from the Wairau River – its pristine water has flowed from the snowcapped Southern Alps down here, to the west of Marlborough.
With this provenance in mind, Will and Knox (our fantastic and first-ever official harvest worker) spent some hours down by the Wairau River picking up boulders and seeing how they felt about them. In a hard-to-describe way, they said some rocks just felt better. It’s similar to how some places feel more welcoming than others but you can’t quite articulate why.
The science perspective
The winemaker in me sees the stones with two potential impacts once they’re in a barrel.
First, they could influence fermentation by being both a cold and heat sink. We hoped the stone would initially act like an ice block, keeping the juice cooler for a longer period prior to ferment. Then, once ferment had started, the stone could act as a natural heat conductor by absorbing heat generated during the fermentation, and gradually radiating it back into the juice. This heat transfer would have the greatest impact at the end of the fermentation, when the increasingly alcoholic juice (by then almost wine) becomes more toxic to the yeast – the additional heat from the stone could help the yeast to cope and complete the fermentation successfully. The heat from the stones could also aid in the breakdown of the yeast (yeast autolysis) helping to produce a richer, rounder palate.
Secondly, the influence of the oak barrel changes with the addition of the stones. The stones take up roughly 10% of the volume inside the barrel, which leaves the remainder of the juice/wine in greater contact with the oak barrel, potentially intensifying the oak flavours in the wine.
The results
Clearly, this is an experimental approach we hope will teach us more about the impact of the vineyard on our wine style. In six months’ time, we will start to analyze the results – it is perhaps only after we have completed this experiment for three years that we will really see if it has enhanced the site-specific character the stones bring to our wine.