In Malolactic Fermentation and Bacteria
This morning I was looking at some results from MLF trials done in Italy during the 2009 harvest season and once again the benefit was overwhelmingly on the side of co-inoculation of the bacteria with the fermenting yeast. Over the past few years I have seen various research reports, published articles and powerpoint presentations at conferences on the topic of co-inoculation. Every time the co-inoculated MLF result is better than inoculation after alcoholic fermentation and certainly streets ahead of the spontaneous fermentation results. Why is everybody not doing it? Well the answer to that question in my humble opinion is two-fold:
1. "Fear” because people think that inoculating for MLF before alcoholic fermentation is completed, can have the bacteria grow on sugar instead of malic acid, and as a result form volatile acidity. This is after all what happens in the case of a stuck fermentation. So the fear is justified, but in the case of stuck fermentations it is the natural lactic acid bacteria present on the grapes that cause the havoc. The specific commercial bacteria trialled and tested in the case of co-inoculation do not produce VA. There exists enough evidence for this now.
“2. "Cost” because MLF can happen automatically and it won’t cost you a sent. In these economic times many winemakers go for this option. Some people buy a small amount of commercial cultures and then “mother tank” them. However, to ensure a successful MLF, just like a successful alcoholic fermentation, one needs to inoculate a certain population size. By inoculating less, you could run into a stuck MLF which will cost you more to resolve than what inoculating adequate amounts of the starter culture would have cost you in the first place.  There are various other advantages of using specific bacterial starter cultures versus spontaneous – biogenic amines and sensory attributes to name but two.
Inoculating after alcoholic fermentation means you inoculate bacteria into very harsh conditions of high alcohol concentrations and possible non-optimal temperatures, since red wine production is towards the end of summer / autumn and cellar temperatures can drop quite substantially. So, you take your chances with a low inoculum due to “mother tanking” into harsh conditions and you expect it to work perfectly every time? These types of practices make me very nervous. I like things to work. My personal view on this is that if you are into quality winemaking you should not be taking any unnecessary chances. Companies selling bacterial starter cultures can only guarantee a successful outcome to some extend if you follow their instructions and use the bacteria under the conditions they are suitable for.
Personally I would go for co-inoculation. Why? Well you inoculate the bacteria into juice with no or very little alcohol. How nice is that for the bacteria??? The temperature is also very optimal for the bacteria since yeast produces a significant amount of heat during fermentation. The only thing is that one should ideally keep the temperature in the mid 20’s (degrees Celsius) since that is what will be optimal for the yeast / bacterial combination. It is anyway a good idea in the case of the yeast as well, since high fermentation temperatures increase ethanol toxicity. In most of the trial results I have seen, MLF is completed when AF is completed. The time saving and energy saving (no heating up of tanks) can have a profound effect on your bottom line. Generally one has to inoculate the bacteria 24 hours after the yeast inoculation. The reason for this is to give the SO2 that was added at crushing time to bind since free SO2 can have an inhibitory effect on lactic acid bacteria. With co-inoculation there are no short cuts. You have to use the inoculum size specified by the supplier as well as use only bacteria proven suitable for co-inoculation. Suppliers also specify the yeasts that are best suited for the co-inoculation.
So, it will cost you, but you will get what you pay for: a more predictable and reliable outcome and latest research shows there is a sensory advantage as well!!! Sounds like a good deal to me. The company that I am forced to work for since I did not marry into money employs an American marketing consultant who would have ended off this blog with the following words:
Can you afford NOT to be part of this REVOLUTION???!!!
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