Malolactic fermentation inhibition

Gerbaux, V., VUla, A., Monamy, C. Bertrand, A. (1997). Use of lysozyme to inhibit malo-lactic fermentation and to stabilize wine after malolactic fermentation. Am. J. Enol. Vitic.,48, 49-54. 

Microbial interactions that occur in wine may be beneficial or detrimental to wine quality depending on the species involved. Examples of detrimental interactions are the inhibition of S. cerevisiae by Lactobacillus species and the inhibition of O. oeni by S. cerevisiae when MLF is desired. However, the inhibition of O. oeni may also be beneficial to wine quality if MLF is undesirable. Additional beneficial interactions include the stimulation of LAB growth due to yeast lysis and the inhibition of Pediococcus species by O. oeni. A better understanding of the complex interactions between LAB and S. cerevisiae will lead to the selection of compatible yeast and bacterial strains for the induction of alcoholic and malolactic fermentations. 

Caridi, A. and Corte, V. 1997. Inhibition of malolactic fermentation by cryotolerant yeasts. Biotech. Lett. 19, 723-726. 

Lonvaud-Funel, A., Joyeux, A., and Desens, C. 1988. Inhibition of malolactic fermentation of wines by products of yeast metabolism. J. Sci. Food Agric. 44, 183-191. 

Henick-Kling, T., T.H. Lee, and D.J.D. Nicholas. 1986a. Inhibition of bacterial growth and malolactic fermentation in wine by bacteriophage, f. Appl. Bacteriol. 61 287-293. 

Hood, A.V. 1984. Possible factors affecting sulfur dioxide inhibition of lactic acid bacteria in newly-fermented wines. Malolactic Fermentation. Aust. Soc. for Viticulture and Oenology, Inc. 

PiLONE, G.J., B.C. Rankine, and A.D. Pilone. 1974. Inhibiting malolactic fermentations in Australian dry red wines by adding fumaric acid. Am. J. Enol Vitic. 25(2) 99-107. 

Osborne, J.P. 2005. Inhibition of the malolactic fermentation by Saccharomyces cere-visiae during the alcoholic fermentation. Ph.D. Dissertation. Washington State University, Pullman, WA. 

In spite of all precautions, a stuck fermentation may still occur. In this case, white wines must be treated differently from reds which undergo malolactic fermentation. At the time of the stuck fermentation, the red wine tank contains must and pomace rich in bacteria. The wine should be drained rapidly, even if the skin and seed maceration is not complete. Draining eliminates part of the bacterial contamination and introduces oxygen, which favors the restarting of fermentation and decreases the temperature. The wine can be sulfited at the same time, to inhibit bacterial development. In some cases, the fermentation restarts spontaneously. 

The ideal temperature for lactic acid bacteria growth (notably O. oeni) and for malic add degradation in wine is around 20°C. An excessive temperature of 25°C or above always slows malolactic fermentation—principally by inhibiting the bacterial biomass. Additionally, an excessive temperature increases the risk of bacterial spoilage and increased volatile acidity. In practice, therefore, maintaining a wine at 20°C is recommended. It should not be allowed to cool too much after alcoholic fermentation. If the temperature of the winery decreases, the wine should be warmed. 

In white winemaking and for wines in which malolactic fermentation is not songht, snlfiting can be adopted to inhibit bacteria completely. Incidentally, the light sulfiting of white mnsts nndergoing malolactic fermentation can be insnfficient to protect effectively against oxidation. 

At the end of alcoholic fermentation, malic acid concentrations should be determined and monitored if necessary. Malolactic fermentation (MLF) normally occurs after the complete depletion of sugars. An early initiation of MLF is generally linked to alcoholic fermentation difficulties and insufficient sulfiting. In certain cases, the two fermentations take place simultaneously, even though the antagonistic phenomena between yeasts and bacteria tend to inhibit alcoholic fermentation. 

As acidity inaeases, a growing number of bacterial species is inhibited. Malolactic fermentation becomes increasingly difficult but, simultaneously, it is increasingly pure. Malic acid is predominantly degraded. The degradation of other wine... 

Adding sulfur dioxide when the must is put into vat also has an impact on malolactic fermentation. The fermentation may be delayed to a variable extent, depending on the concentration of sulfur dioxide used and the way it is mixed into the must (Section 8.8.1) and may, in extreme cases, even be permanently inhibited. The concentration chosen must be sufficient to retard malolactic fermentation, to avoid its interference with alcoholic fermentation and the associated risks, but not so excessive that the malolactic fermentation cannot be completed within a reasonable time period. 

As soon as fermentation is nearly complete, the barrels are topped off with juice from the same lot. Sluggish fermentations can often be reactivated by topping off the barrel with a wine lot that has recently completed a successful fermentation. This technique is equivalent to using a starter (10%) composed of a population in the stationary phase—resistant to inhibition factors. At the end of alcoholic fermentation, the barrels are stirred daily until sulfiting (Section 13.7.6). Wines undergoing malolactic fermentation are not sulfited until its completion. 

Patynowski et al. (2002) showed that yeasts produce an unidentified inhibitory factor (maybe a toxic metabolite) that could be responsible for the inhibition of bacterial growth. These results could explain the antagonism between yeasts and malolactic bacteria, since yeasts are known to produce compounds during alcoholic fermentation such as ethanol, SO2, medium-chain fatty acids and antibacterial proteins/peptides (Weeks et al. 1969 De Oliva et al. 2004 Comitini et al. 2005 Osborne and Edwards 2007). The nature and quantity of peptides and other molecules released by yeasts are different depending on winemaking techniques and the yeast strain. 

In addition to S02 and antibacterial proteins/peptides, medium-chain fatty acids produced by yeast during alcoholic fermentation have also been implicated in the inhibition of malolactic bacteria (Carrete et al, 2002 Edwards and Beelman, 1987 Lonvaud-Funel et al, 1985). Inhibition of Saccharomyces species and some LAB by medium-chain fatty acids has been reported in grape juice and silage (Pederson et al, 1961 Woolford, 1975). Although this hypothesis has not been conclusively shown, Lonvaud-Funel et al (1985) and... 

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