Staphylococcus biofilm. Image courtesy Wikimedia Commons
Cleanliness is next to goodliness in home winemaking. I’m not sure who said this, but the crashing bore was completely correct: nothing can spoil a batch faster than bacteria or wild yeast living on the remains of a previous effort. That’s why winemakers are always vigilant with rinsing bottles after they’re empty, and slosh sulphite around their equipment with great abandon. Keep your equipment and bottles free of debris and treated with a bacterial suppressor like sulphite solution and it will always be ready to go, right?
Sadly, not always—in fact this regimen can leave your equipment a cause of failure, rather than a source of success. Simple rinsing may remove visible residues from surfaces, but after repeated exposures to batch after batch of wine even the ultra-smooth surfaces of glass carboys will develop an invisible layer of colloids and proteins, sometimes described as a bio-film.
This film is analogous to the film that develops on your teeth. And, just as in keeping carboys clean, if you only rinsed your mouth after eating, and perhaps took a swish of mouthwash, you would, in a very short period, find yourself with a serious oral hygiene issue.
Even soaking equipment in quite powerful oxidising cleansers (chlorine-based powders, peroxides or bleach) or powerful reductive agents (sodium hydroxide/caustic soda) won’t completely remove biofilms. This requires the mechanical action of scrubbing to remove the film. Again, we can go back to teeth: even if you rinsed with very strong mouthwash, you still need the mechanical action of brushing to remove the debris from tooth surfaces to be kissing fresh....