Winegrowers Supplies  -  Sterilising bottles or equipment

Using Sulphur dioxide (SO2) or Peracetic acid as sterilant?

Sulphurous acid is a colourless solution of sulphur dioxide in water, with the formula H2SO3, characterized by a suffocating sulphurous odour. It is different from sulphuric acid H2SO4.

Bryce Rankine states Sulphurous acid strength (in % SO2) against Contact time in seconds to sterilise an empty bottle:-
                                              0.5                                                                  60
                                              1.0                                                                  45
                                              1.5                                                                  30
                                              2.0                                                                   5

Typically, 2% Free SO2 solution would be used as the bottle sterilising solution.

Peracetic acid, typically as a 1% solution, needs much longer reaction time in the bottle (at least 10 seconds), so the operation would have to run at one fifth of the speed (2 seconds contact time with SO2 is enough); a larger machine would hence be required for a particular throughput.

Peracetic acid is a very powerful cleanser and disinfectant; it's oxidation potential outranges that of chlorine and chlorine dioxide. In concentrated form it must be handled with great care; rubber or Neoprene gloves must be worn.
When peracetic acid dissolves in water it disintegrates to hydrogen peroxide and acetic acid, which will fall apart to water, oxygen and CO2, these degradation products are non-toxic and can easily dissolve in water.

SO2 is much more corrosive, so a stainless steel tank holding an SO2 solution for a long time would need to be made in AISI-316 rather than AISI-304, more likely it will be made in plastic.
A vapour aspiration system is necessary to remove fumes, a good extractor fan in the room can be sufficient.