The single most important aspect of mead brewing: more important than your choice of honey varietal or adjunct, more important that fermentation or racking intervals, more important than bottling or aging methods, more important, even, than the oft debated choice of boiled honey versus natural honey, are the methods used in sterilization. While a poor combination of spices can make a mead slightly less than perfect, inadequate sterilization can corrupt a batch to the point of unpalatability.
Saccharomyces cerevisiae and Saccharomyces uvarum, the two most common forms of brewing yeasts are jealous fungi. They are generally intolerant of the presence of other forms of fungus in their habitat and will force competing yeasts out. A number of other microorganisms, mostly bacteria, can survive easily in the presence of brewing yeast and will contaminate the product and some can even make us humans that consume it quite ill. Preventing the propagation of these invaders is even more important when one remembers that most mead is made with entirely organic, unpasturized ingredients.
Generally, the home brewer has three means of sterilization available to them. Many brewers choose to chemically sterilize with a solution of potassium metabisulfite. This common anti-bacterial and anti-fungal agent is available for a few dollars at any brew store.* It is easy to use and performs its function quite well.
Similar to this, although more mundane, one can sterilize chemically with hospital grade isopropyl alcohol. Be sure to read the label carefully, most first aid quality rubbing alcohol is 70 or 80 percent alcohol, while the hospital quality I'm referring to is 90 percent or better. Pour it liberally into and onto all brewing gear being sure to cover every surface and then rinse thoroughly with very hot water. If you have sensitive skin you might want to wear gloves. Be sure to do this with the windows open or the fan on or you run the risk of having your kitchen smell like a hospital for days afterwards.
Finally, the most traditional, and probably the best means of sterilization is the good old fashioned hot kill. Boil all of your equipment for three minutes or longer. Mind you, some gear, like plastic tubing and rubber stoppers may melt at these temperatures so be careful. This should kill all but the heartiest microorganisms. Carboys may be too large to boil, in which case, rinse them completely several times with boiling water being careful to heat the glass evenly lest it shatter.
I use a combination of these two techniques. I clean all of my tools and containers with rubbing alcohol and then rinse them with boiling water.
More important than the means of sterilization is the thoroughness of sterilization. You must sterilize absolutely everything involved in the brewing and bottling process, carboys, airlocks, hoses, dump buckets, mixing devices, funnels and hand tools. Clean your work area and then wipe it down with some kind of sterilizing solvent, bleach based home cleaners like Fantastik work well. Sterilize your bottles when you package your product. If you are bottling your mead in 750ml wine bottles, like I do, always buy brand new corks in the sealed plastic bag. If you reuse bottles, be sure they are adequately cleaned and sterilized exactly as you would sterilize your other gear. And, for the sake of all that is holy, wash your hands. Wash them in the hottest water you can tolerate; wash them up to the elbow and wash with a heavy antibacterial soap.
I cannot stress the importance of this enough. While most of the little beasties that inhabit both your home and the natural products that go into your brewing are harmless, some are not. Some can halt fermentation or produce foul flavors. Some will infuse sulfides and other nasty chemicals into your product. The vast minority are infectious and can make you and the people that drink your mead extremely ill. Be fastidious, even anal, about your sterilization methods and you will be saved a lot of headache.
Remember this and everything else is just technique.
* Personally, I do not use this method. When I stabilize my mead, something I will discuss in detail in a later post, I do so with the same chemical, albeit in a much more dilute form. I am concerned about breeding resistance to the chemical into my yeast strains. Understand, I do not dis-advocate it's use, I simply choose a different method.