w i n e M A K IN G
Monitoring methods: Sensory cues, microscopic exam, PCR
Most commercial freeze-dried cultures are produced following extensive quality assurance procedures to be sure they are
free from contaminants. Once they are put into must or wine,
however, the resident bacterial flora may grow along with, or
instead of, the inoculated strain(s).
Check wines during MLF for spoilage bacteria, at least microscopically and also by PCR methods, if possible. This is especially important if the culture is propagated before adding it,
allowing unwanted lactic acid bacteria more opportunity to
grow as well (or instead), and also giving aerobic yeasts and
acetic bacteria a chance to spoil the starter. Acetobacter growth is
particularly unfortunate in ML starters and during MLF. Microscopically, it is sometimes confused with Oenococcus.
If Lactobacillus and/or Pediococcus are a significant part of the
wine's bacterial flora, it may be best to kill them with lysozyme
and reinoculate with a resistant Oenococcus strain. However, if
the wine is dry, the winemaker may decide to accept the presence of some Lactobacilli during MLF, despite a tendency to
introduce "pickle" or "sauerkraut" aromas.
Pediococci can make lactic acid but not acetic acid from sugar.
They are considered undesirable mainly because some can continue growing after wine is dry and has finished MLF, and
because of biogenic amine production, though off-flavors
("dirty socks") have been ascribed to some strains.
In cellars heavily infected with Brettanomyces, culturing once
each week or testing with PCR during MLF is recommended.
PWV
Lisa Van de Water, known as "the bad wine lady," can be reached at
www.vinotecnapa.com or badwinelady@aol.com.
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64 p r acti c al w i ne ry & v i ne yard JANUARY 20 14
