Which factors influence MLF? Several well-known factors such as pH, alcohol, temperature and SO2 must be well adjusted in order to favour the development selected malolactic bacteria. Those factors function synergistically and a favourable level of one factor may compensate for an unfavourable one. Assigning a precise value to each factor is difficult, but it is crucial to abide by the parameters defined by the producers of the malolactic bacteria (MLB) cultures. This is perhaps the most important consideration to ensure a successful MLF. Some of the lesser-known factors that can influence the course of MLF have been recently studied. Such factors as tannins, yeast strain compatibility, nutrient deficiencies, lees compaction, residual lysozyme activity, excessive amount of oxygen, fungicide residues, initial malic acid concentration, fatty acids and certain peptides can have an impact on MLF. Because they are lesser-known does not mean that their impact is less significant. For example, grape tannins of certain varietals such as Merlot can cause great difficulty to MLB. Also, some MLB strains are more sensitive to phenolic acids, such as ferulic acid and p-coumaric acid. A support in specific nutrients can limit those inhibitions or help to overcome them. Certain fungicides and pesticides are also detrimental. For example, systemic compounds used in humid years to control botrytis fungus can harm the course of MLF. Special care must be taken in high botrytis contamination years and prescribed withholding periods must be respected for each product. A successful MLF means that the starter culture is able to reach and maintain high cell viability. Sufficient levels of the fatty acid, oleic acid, have been shown to be essential for this event. High must clarification can deplete the medium of this fatty acid and negatively influence the MLF. It can be counteracted by inoculating with very high cell numbers. Medium-chain fatty acids (C6 to C12) and peptides between 5 and 10 kDal derived from yeast metabolism on the other hand can have a negative impact on the course of MLF.

If you wish to know more about MLF conditions that could affect MLB, please consult or request the Malolactic fermentation in wine reference book written by bacteria specialists in collaboration with Lallemand or consult your Lallemand representative.

In order to succeed in your malolactic fermentation, different factors are important. To determine the ease of your malolactic fermentation, you can have a look at the following table.