Wine bacteria. More important than yeast?

Last week I nipped over to London for the day to attend the latest in a series of talks from Yeast developers Lallemand at the Institute of Masters of Wine. The on-going discussions over Sulphur Dioxide (SO2) in winemaking and general misunderstanding surrounding some winemaking practices drives me to learn more whenever I can. Bacteria in wine, there’s only one beneficial form and that’s oenococcus oeni right? Wrong.

For those of you out there looking for some geek induced information; there are four main genera associated with winemaking, these are:

  • lactobacillus
  • leuconstoc
  • oenococcus
  • pediococcus

Oenococcus oeni gets nearly all of the attention, mostly due to its high resistance to ethanol.

Bacteria is like the kitchen worker in a busy restaurant. Out of sight, forgotten even, but a vital part of the workings in the business. The first to be blamed if something goes array… think acetyl acetate (nail varnish), this is a direct result of the acetobacter in a vulnerable must. A fatal smell that immediately flags the negative activities of this particular strain, taking from the silent, beneficial work that other bacteria are practicing.

So yeast is bigger? True about 10 times the size. Better? This is open to question. Yeast can do more? Nope, bacteria have a myriad of capabilities, malolactic fermentation (MLF) is just the beginning. Unlike yeast and certain strains associated with vineyard location, bacteria is linked to environmental conditions. Trials at Lallemand have shown that different strains of bacteria favour different conditions, the strain prevalent in wines with low pH is different to the one inhabiting wines with high alcohols. Resistance to the elements in wine determines which bacteria exist there. Food companies have a firm grip on the benefits of Lactobacillus using it to inhibit spoilage bacteria with its production of lactic acid. Wine producers are starting to follow.

The complexities of bacteria are greater than yeast

Like with yeast, Lallemand work through a selection process to find the best Bacteria (sounds like a joke right). They screen the different strains for suitability in certain conditions – high acid environments, alcohol and temperature extremes and different SO2 concentrations are referenced. It takes a minimum of five years for a commercial bacteria to reach the market. Modern winemaking is under far greater scrutiny for faults than in the past. The trend for lower sulphur wines has opened the gates to far more ‘funky’ odours caused by oxidative or bacterial interference in the wines, prevented in the past by the antioxidasic and antiseptic properties of SO2. We are seeing increased occurrences of:

  • Mousy taint (100% due to bacteria)
  • Sensory cinnamyl issues (not just from Brett, bacteria also play a part)
  • Increasing levels of biogenic amines

The impact of these sensorial factors not only takes away from the translation of terroir in the glass, but also the enjoyment of the drinker. This is why research is on-going to harness the potential of beneficial bacteria, using it in an educated way to help maintain the purity of wines and lower SO2 levels in the long-term.

Hello ‘Super strains’ or ‘Barry’, the berocca of bacteria. These isolated super strains of bacteria can:

  • Survive 50mg/L total SO2
  • Conduct MLF at low temperatures
  • Survive alcohol levels up to 16% abv
  • Live in musts with pH as low as 2.8 and as high as 4.5

And here’s the really interesting bit… these microscopic bacteria can actually:

  • Enhance an aroma profile
  • Keep volatile acidity levels (VA) close to zero
  • Produce no off flavours whatsoever
  • AND cease the production of biogenic amines

In case you didn’t know BIOGENIC AMINES are toxic to humans. Alcohol slows the degradation of these in our system. Research shows that these are contributors to the ill effects felt after a heavy drinking session. Are you listening now?

Bacteria only produce biogenic amines when they’re stressed. Lallemand’s selected strain LAB produces less than 1 mg/l of histamine and tyramine (biogenic amines). Indigenous flora coming in from the vineyard on grapes produced Histamine levels of 13.8mg/l. The differences seen below are self explanatory.

Co-innoculation is key. The beginning of fermentation ensures greater nutritive resources for the bacteria, reducing stress and more importantly a quick and efficient fermentation and MLF prevents extended access to destructive bacteria which could add complexing factors that take from the expression of the vineyard and degrade over time into off flavours.

What I found particularly interesting was that there is a misconception that when fermentation is finished there are no sugars to feed other microbial activities in the wine. WRONG. The infamous strain of yeast Brettanomyces feeds from unfermentable sugars still in the wine post fermentation. (This is why brett infested wines taste so dried out.) Brett grows even at low temperatures in a wine innocently open to this invasion. In Burgundy two weeks ago, I heard many producers talk about their natural ferments and natural MLF occurring in the spring post fermentation. The cool temperatures ‘protecting’ the wines till both had occurred. This teamed with lower SO2 levels allows massive bacterial interference. Perhaps this is why Kitosan (a very effective tool for killing Brett) enjoys very successful sales in Burgundy.

Beating brett through prevention rather than cure. Lallemand have launched a biocontrol offensive in the form of a specially selected bacteria that actually removes brett strains from the must. Trials have shown that when a fermenting must was innoculated with this strain the levels of Brett went down to almost zero. There is no definite explanation but this super strain seems to expel toxins that inhibit brett, whilst using up the nutrition that it relies on, literally starving it to extinction in the wine. Following these studies the OIV is advising co-innoculation in all fermentations.

This piece takes just a small slice of some of the discussions from last week. I think the resounding message from the panel was the dangers of not knowing.

As Sam Harrop MW pointed out:

“Characteristics of spontaneity mask place”
and “having this toolkit [bacteria] enhances diversity”

Take home message? Bacteria can be harnessed to reduce the use of SO2, highlight the aromatic profile of a region, reduce the toxic biogenic amines and channel terroir into the glass without interference from microbes that disguise this expression with their own off aromas and flavours.

“These products are not additives, they can be used to reduce the level of additives.”

Sam Harrop MW

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