Agriculture Reference
In-Depth Information
this, we'll need to remove the free sulfite from the solution.
The 3% hydrogen peroxide solution is way too strong for a
sample this small, so make some 0.012% solution by adding
1ml of hydrogen peroxide solution to 250ml volumetric flask
and adding enough distilled water to meet the 250ml mark.
Clean all equipment with distilled water. Put a 20ml sample
of wine in the 50 ml beaker. Add an amount of your prepared
hydrogen peroxide solution equal to 0.14 ml for every ppm
detected in the earlier procedure. So if the first procedure
gave a result of 57ppm, add 0.14 x 57 or 8 ml of hydrogen
peroxide solution. Swirl to mix and wait a few minutes. Add
5ml of starch solution and 5ml of sulfuric acid solution to the
sample. Fill the 3ml syringe with iodine solution. Add iodine
solution a little at a time, swirling after each addition, until a
distinct color change (it will be dark blue) that remains for
several seconds occurs. The measured amount of error in ppm
is:
(3ml−reading on syringe) × 32
The corrected amount of sulfite in the wine is: (measured
sulfite)−(measured error) ppm.
Malolactic Fermentation
Most wine musts will contain some lactic bacteria. These are
inhibited by sulfite levels greater than 20 mg/L, by alcohol
concentrations of greater than 14%, low temperatures, and
active yeast. If you have ever been quite certain that
secondary fermentation has completed but later found your
bottled wine to be slightly carbonated, it is likely that
malolactic fermentation occurred spontaneously. Sometimes
