Timing of LAB Addition

Winemaker s opinions vary as to the timing of starter inoculation. In the survey of Fugelsang and Zoecklein (1993), 41% of red wine producers added starters during the course of alcoholic fermentation, 17% at the end, and 17% after pressing at the end of extended maceration. The situation was quite different for white wine producers 25% inoculate at the same time as yeasts, 15% early in alcoholic fermentation, 48% at some stage of later fermentation, 9% upon completion (but before first racking) and 3% after first racking. 

Much of the concern with LAB inoculation at the start of fermentation stems from reports of rapid bacterial utilization of sugars before onset of alcoholic fermentation. In the case of heterofermenters delay in the onset of alcoholic fermentation may stimulate bacterial production of acetic acid resulting in inhibition of wine yeasts and thereby increasing the potential for stuck alcoholic fermentations. 

One commercial LAB starter (Vinflora LP, available through Chris Hansen Laboratory) is marketed as a freeze-dried culture for prefermentation addition to juice/must. In this case, MLF is initiated and partially carried out in advance of alcoholic fermentation by the addition of a high-titer inoculum of the homofermenter Lactobacillus plantarum. Being homofermentative, any utilization of glucose at this stage yields lactic acid solely. However, the strain is relatively susceptible to alcohol thus, activity 

It is not uncommon to find winemakers utilizing wines and/or lees of ongoing, or recently completed MLF, as inocula for lots needing to undergo MLF. Assuming that the blend does not create problems in terms of varietal and appellation requirements, this technique reduces both the amount of commercial starter needed and the time involved in rehydration, expansion, and acclimation. 

It should be noted, however, that compared with properly prepared starters where population densities may exceed 10 CFU/mL, cell density in wine undergoing MLF is considerably less. Thus, much larger inoculation volumes (10-25% v/v) may be required to reach levels of 10 CFU/mL (Firme et al., 1994). 

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