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Malolactic fermentation (MLF) is the bioconversion of the L-malic acid in wine in to L-lactic acid and carbon dioxide. It can be caused by various lactic acid bacteria although it is generally associated with three genera: Oenococcus, Lactobacillus and Pediococcus. MLF can be suppressed by adding lysozyme. This versatile egg-white enzyme fights bacteria ; controls MLF and can reduce reliance on sulfites. Besides deacidifying the wine, MLF improves the biological stability of wines by preventing the malic acid utilization by other non-desirable species. Moreover, during MLF the bacteria also can affect the final aroma balance by modifying fruity aromas and maybe producing aroma active compounds by themselves. A major disadvantage of MLF is the unpredictability of its occurrences and control during vinification. MLF and evolution of lactic acid was registered using TLC. Volatile compounds were analyzed by static headspace sampler coupled with gas chromatography with FID. In wine with lysozyme (0.5g/L) (lallyzime lyso ; Lallemand) MLF started after cca 100 days. Natural wine microflora started MLF after twenty days and finished after forty days. pH was changed from 3, 82 to 4, 02. Wines, which had undergone the MLF, showed a significant increase in ethyl acetate, diacetyl and ethyl lactate that are important for the sensory properties and quality of wine. Acetaldehyde during the MLF decreased on level of 1 mg/L. In wine which didn’ t undergo MLF, acetaldehyde increased up to 10 mg/L. Diacetyl started to fall during the end of the MLF. In wine with MLF suppression compounds did not change until there was not bacterial activity. Lysozym suppressed the MLF successfully, but it had lost its activity after cca 100 days. The wines which had undergone the MLF, showed an increment of aroma compounds. |
