I just started home brewing, have studied up on the issues associated with methanol/fusel alcohols, and I'm wondering if there are certain practices that can be used to minimize non-ethanol alcohols, or other harmful things in home brews?
I've heard that the first ferment of wine should be anoxic, but then I hear in other places that it needs oxygen, or might produce more fusel alcohols.
What about nutrients? agitating the brew? other factors?
Yeast needs nutrients and oxygen mainly for their growth phase. This can be substituted by pitching a massive amount of yeast. For example pitching wort on top of a yeast cake from a beer that just finished primary.
Methanol is formed when fermenting beverages high in pectins - eg grapes and berries. The methanol comes from the pectin, which mainly composed of methyl esters of galactose. When pectin breaks down, by enzymes introduced by micro organisms, or deliberately introduced, the methyl esters combine with water to produce methanol, so the aim should be to leave the pectin well alone if you can. Age clarify instead of pectic enzyme. Trying for an abv higher than 12% will also increase the risk of methanol being produced.
Various sources of yeast stress can cause fusel production during fermentation, but excessive must heat is by far the most common cause. Methanol may also be produced, especially if your must temp is above 72F. I'd recommend trying a high heat tolerant yeast strain like EC 1118.
In my experience, fusel production with EC 1118 is nonexistent, and you'll end up with one of the cleanest tasting meads that you've ever tried. Try to keep your mead at or below 70F and remember you have to feed it properly for the yeast to preform the magic act it does.
Fermaid K at the rate of 1 gram per gallon at must start, when rapid initial start slows, and every other day up untill the 1/3 sugar break is good for tradional style meads. Meads with fruit will have nitrogen etc. available to the yeast so 1/2 that rate will suffice.
I airate my must at the start with a fish tank pump and airstone for 15-20 minutes. I do this once more after the initial slows down too. Musts with fruit should have the fruit cap punched down twice a day for 7 days, introducing as much oxygen into the must as possible.
These are two different questions. I'll add some new information on Methanol since this question was asked a couple of years ago. Generally in western countries where we have access to cultured yeasts, methanol is not a problem. But in many less advanced countries, methanol production is a problem and this new paper suggests that it's do to some wild yeasts that are used.
Incidences of methanol contamination in traditional beverages are increasing globally and have caused death in many counties including Nigeria, India and Indonesia. It is generally believed that unscrupulous vendors deliberately spike the beverages with methanol in order to increase the alcohol content. This review observed that methanol production in traditional fermented beverages can be linked to the activities of pectinase producing yeast, fungi and bacteria. Microbes producing pectin methyl esterase are able to produce methanol from fruits/juices containing pectin. Under traditional/informal fermentation, alcoholic beverages produced by mixed microbial consortium could probably lead to the production of mixed alcohols containing methanol and other volatile congeners. The study concluded by suggesting that contaminated alcoholic beverages be converted for fuel use rather than out rightly banning the age—long traditional alcohol fermentation. Regulatory limits for methanol in fermented beverages should be strictly enforced. It is also suggested that pure cultures should be used for alcohol fermentation under aseptic conditions as opposed to spontaneous fermentation by mixed contaminating microbes.
Here is a link to the paper "Methanol contamination in traditionally fermented alcoholic beverages: the microbial dimension"
