Zinc
in Wort prior to Pitching
General Considerations
• Zinc is an essential trace element required for
yeast growth and therefore insufficient zinc will lead to slow or
sticking fermentations.
• There is no general correlation between the zinc content of the
malt and that of wort because of variable losses in spent grains
and trub.
Range of Values
• It appears that the normal range is 0·05 - 0·1
mg per litre but up to 0·25 mg per litre may be necessary. The amount
needed depends on yeast strain used, process conditions and the
concentration of chelators. Too high a level can, in some cases,
lead to yeast autolysis and, therefore, produce sulphury off-flavours.
Operational Protocols
• Normally sufficient zinc is extracted during
wort production but where deficiencies occur, or as a precaution,
zinc can be added as a constituent of yeast food or as zinc sulphate
or chloride. It is therefore desirable to check the zinc content
of the wort at regular intervals and particularly in cases of fermentation
difficulties.
Measurement Protocols
• The concentration of zinc is measured using an
Atomic Absorption spectrophotometer.
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