60 P R A C T I C A L W I N E R Y & V I N E YA R D April 2015
R E S E A R C H F O C U S
different wineries and compared five treat-
ments: sulfur dioxide, peroxyacetic acid,
steam, chlorine dioxide and ozone.
Each treatment was applied at varying
concentrations (peroxyacetic acid, chlorine
dioxide) or varying lengths of time (sulfur
dioxide, steam, ozone). Each barrel was evalu-
ated before and after treatment, and the total
yeast populations —Zygosaccharomyces bailii
(a re-fermentation risk) and Brettanomyces
yeasts (see above) — were compared.
Wood core samples were taken before
and after treatment to count cells below the
surface.
Sulfur dioxide (SO
2
) is the preferred pro-
tective additive used in wine because of its
dual antioxidant/antimicrobial abilities. In
this case, sulfur discs are burned in clean,
dry, empty barrels. These discs create gas-
eous SO
2
, which prevents the growth of
microorganisms over a long period of time.
In this study, barrels were evaluated after
three and six weeks. The longer treatment
time was found to be statistically just as
good as the shorter one, indicating that
effective sanitation can maintain spoilage-
free conditions for long periods of time pro-
vided there is no re-contamination.
Peroxyacetic acid (PAA) is a mixture of
peracetic acid and hydrogen peroxide, which
is an effective sanitizer over a wide range
