As previously explained (see section regarding which factors influence malolactic fermentation), the vat's environment can be more or less fermentable depending on various criteria, the most important being the pH, ethanol and temperature. An easily fermentable environment does not require inoculation.
If organoleptic deviations described in the previous chapter have been previously encountered, this often indicates that the indigenous flora in the winery tends to produce deviations. In such cases, special attention to hygiene should be implemented as well as inoculation.
When the malolactic fermentation is sluggish or very late, the environment is favourable to B. bruxellensis development, which produces phenols with animal-like odours. They can develop at the same time as lactic bacteria. A slow fermentation should therefore be avoided for wines that may favour the development of this yeast.
In the case where the environment is easily fermentable and where there is no history of deviations due to lactic bacteria, indigenous MLF can be considered without any concerns, as long as the monitoring and temperature controls are carried out rigorously.
Similarly, for highly selective environments containing few phenolic acids, the risks for MLF are reduced. This is regularly the case with Pinot Noir where MLF sometimes takes place after the first winter of ageing and very often without any organoleptic deviations.