Yeast on the rise

(L-R): Neudorf Pinot Noir, Cottage Block chardonnay, and Cloudy Bay. Photos/ Babiche Martens, Supplied

Little has been known about the mysterious world of wild yeasts, despite the fact they've been helping humans transform simple grape juice into more flavoursome and aromatic wines since the dawn of civilisation. However, groundbreaking research conducted by Auckland University's Dr Mat Goddard has started unravelling their secrets and discovered that New Zealand has a unique selection that could be harnessed by our winemakers to make the country's wines even more distinctive.

"The contribution that yeast makes to wine has been significantly underestimated," says Goddard, whose fascination with these fungi has brought him to the forefront of international research in the area.

"Many of the compounds in wines are produced by yeast, so they don't just use sugar to create ethanol, but are responsible for much more."

In fact, it's been estimated that close to half of a wine's volatile flavour compounds are produced by yeasts.

While it was once assumed yeasts lurked in the winery, leaping into action on the arrival of crates of juicy grapes each harvest, more recently winemakers had a hunch that they came in from the vineyard. However, now Goddard's research has proved they're out there in the soils, flowers and barks around the vineyard, often carried into the winery by insects such as bees.

One of his most exciting findings is that it seems the strains of yeast at large in New Zealand are genetically distinct from those found elsewhere. This suggests that if local yeasts are employed they could play a part in the regional character of a wine, as well as the combination of grape variety, soil, site and climate that's at the root of the French concept of "terroir".

"Terroir was mostly thought of in terms of the geography and climatic conditions in which a variety is grown, but I'm suggesting that there's another component of terroir: the diversity of microbes that reside in a particular region," explains Goddard. "If there are unique communities of microbial species specific to places, these would further differentiate wines that come from that area."

Goddard's preliminary studies also indicate yeasts may even differ between regions.

Our wines may be picking up a little bit of French terroir as well, as Goddard also noted the barrels we widely import from France contain yeast strains likely to be theirs, which play their part in the wines with which they come into contact. So it's not just insects spreading those yeasts around, humans unwittingly do as well.

Nature has provided a diverse array of yeasts that add different characters and complexity to the wines they make, with the so-called wild ferments that allow them to work their wonders used to make most of world's greatest wines.

Despite this, many winemakers today - especially those working with large batches of wine - choose to use packets of single-strain industrial yeasts originating from overseas, due to the risk of feral flavours when wine is left to ferment spontaneously.

Aware of the fear winemakers have of taking a walk on the wild side when thousands of dollars worth of wine is at stake, Goddard has also been isolating less wayward New Zealand yeast strains. They'll be able to use these reliably like the current cultured yeasts, while adding regional colour and complexity to their wines without encountering the side effects of feral ferments.

For a single cell microbe, yeast certainly punches well above its weight when it comes its impact on wine - a bit like our tiny wine industry, which gained an international reputation through its regional styles, which may well become even more individual thanks to our indigenous yeasts.

WILD WINES

TALKING TEXTURE
Neudorf Tom's Block Pinot Noir 2007 $28-$32
Textural complexity is a major element introduced by natural ferments, which is why they're used in many pinot noirs, a variety for which texture is extremely important. This is a seductively supple example with savoury gamey layers interleaved with fresh plums, hints of licorice and wafts of lavender. (From Caro's, Glengarry and Scenic Cellars.)

CHAMPION CHARDONNAY
Cottage Block Chardonnay 2007 $35.95
This multi-award winning chardonnay is proof that wild ferments can give wine a real X factor. Creamy textured, with rich ripe white peach fruit and toasty notes, which are juxtaposed with its juicy line of citrus and mineral. (From selected fine wine retailers.)

NATURAL SELECTION
Cloudy Bay Te Koko 2006 $58.30
Cultured yeasts are widely used with aromatic varieties such as sauvignon blanc as spontaneous ferments can subdue aromas. But it's 100 per cent wild with Te Koko, which, with its rich barrel-fermented butterscotch and nut character infused with subtle notes of sappy herbs and bite of lemon zest, has never been your typical sauvignon. (From Caro's, Glengarry and Scenic Cellars.)