The elimination of contamination is the most important factor in brewing; the one a brewer cannot afford to get wrong.
No matter how good the recipe, how efficient the mashing, how high the quality of ingredients, if the brew is contaminated it’s all for nothing. Poor sterile technique is the one factor that can undermine all the others and ruin a lot of hard work. The only microorganism in your beer should be the fermenting yeast. If only this were always so.
WHAT IS CONTAMINATION?
May sound obvious, after all, we know when a pint is off, but I believe that contamination can be quite insidious. What about lower levels of contaminants that, while not sufficient to be seen as such, are manifested as a taste that lacks the ‘usual flavour’, or is an ‘average pint’, or ‘nothing special?’ Its easy to put it down to a poor mash or recipe, but it might also be that some contamination got in between sterilising and using the fermenter bin, or before a vigorous fermentation got going – especially if there was a long cooling period, and was the wort boiled soon after mashing? Boiling may destroy any contaminants, but even dead bacteria and the compounds they produced while the wort was sitting at cool temperatures, might still taint the brew.