Wellness for Wine. H 2 S-Preventing Wine Yeast. PHYTERRA YEAST Now from Pacific Rim Oenology Services. Why use Phyterra Yeast? Scientific slides by Dr. John Husnik , Phyterra. H 2 S prevention “Preventative” instead of remedial Same features as yeasts already being used
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The difference between UCD 932 and other S. cerevisieaestrains is a single amino acid change: threonine to lysine.
Threonine to Lysine
Threonine is a neutral amino acid, while lysine is charged. The charge apparently prevents H2S from exiting the cell.
Saccharomyces yeasts mating
MET10 allele can be completed
on BiGGYagar, where white
colonies indicate strains not
producing H2S and tan, brown
and black colonies indicate
various levels of H2S production.
Lead acetate strips (black in the presence of H2S) and quantitative analysis confirm no H2S production by a Phyterra strain.
completed on about 50 individual
yeast clones from each breeding
step. Interestingly, each yeast
colony produces different levels of
Total SO2. By selecting low Total
SO2 producers, we can also insure
that not only are these strains H2S-
negative, but also retain similar
Total SO2levels as the Parent Strain.
Aerobic growth, by means of which yeast is produced commercially, is normal for all the crosses.
Common Treatment and Control Methods for H2S
1) Addition of sulphitesto the grapes/must
2) Temperature control especially during cold-soak (not over 10° C)
3) Timely inoculation of must when warmed after soaking
4) Nitrogen supplementation if necessary; winemakers using Phyterra cannot use production of H2S to indicate the need for nitrogen supplementation
Some of these yeasts have the classic round or “egg” shape of Saccharomyces and thus may be Phyterra yeasts, but many have elongated or other odd shapes, so they are different species of yeasts from grapes or cellar sources. These “volunteers” produced H2S.
Products available for 2013 HARVEST
See Page 9 in 2013 PROS catalogue for more details