Sanitizing Counterflow Wort Chillers
Q: Some time back you discussed the proper care and cleaning of counterflow wort chillers (1). I followed your recommended procedure — which included a hot caustic flush, a water flush, and then filling with iodophor until next use — but in about two weeks I nonetheless had “things” growing inside the plastic tube connected to the stainless steel part of the wort chiller. My iodophor solution was 25 ppm and was fresh. I can only see what was in the clear plastic tube and don’t know if the stainless steel is infected or not. I will reflush with caustic before use, but my question is, what on earth could grow in iodophor? I thought I was safe “storing” my wort chiller that way. Is there a better way to store between brews? I thought of perhaps flushing with Everclear (grain alcohol) to absorb the residual water, then air drying. Any suggestions?
A: First, a little reassurance. It’s unlikely that anything was growing in the coil itself. Plastic is much harder to clean than stainless steel. Nonetheless, you are right to reclean and resanitize your wort cooler before using it again. Also, throw out the old plastic hose and get a new one.
As to why something grew in the hose: It can only be because even after your caustic cleaning, some residue remained. Either lengthen your cleaning time, increase the concentration and temperature of the caustic (40 min at 140–160 °F [60–70 °C], with a 2.5% solution recommended), or if you are already following these guidelines increase the pressure you apply during circulation; in other words, get a stronger pump.
How could the iodophor fail? Like any other widely used chemical sanitizer, iodophor is not stable. They all break down with time. Diluted iodophor solutions lose their killing power in three or four days. The loss of power is observable as the solution loses its amber color and turns clear. Once that happens, some organisms can actually feed off the surfactants that are part of the formulation. I have seen mold growing on the surface of a bucket of old iodophor. If your equipment were truly clean, of course, the breakdown of the iodophor would not matter. As it is, if new hoses and a better cleaning regimen do not help, then you will either have to replace your iodophor solution every three or four days, or go to alcohol as a long-term storage solution.
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