Granted molecular sieves do not necessarily remove alcohol fractions.
Molecular sieve, a porous solid, usually a
synthetic or a natural
zeolite, that separates particles of molecular dimension. Zeolites are hydrated metal aluminosilicate
compounds with well-defined crystalline structures. The silicate and aluminate groupings form three-dimensional crystal lattices surrounding cavities in which the metal ions and the water molecules are loosely held. Channels run through the entire crystal, interconnecting the cavities and terminating at the crystal surface. Upon heating, the zeolites lose their water content with little or no change in their
crystal structure. The dehydrated zeolite can reversibly absorb water or other molecules that are small enough to pass through the channels or pores. The metal ions are also readily replaceable by other ionic units of similar charge and size.
Molecular sieves are used for drying gases and liquids and for separating molecules on the basis of their sizes and shapes. When two molecules are equally small and can enter the pores, separation is based on the
polarity (charge separation) of the
molecule, the more polar molecule being preferentially adsorbed.
Water is a "polar" molecule, meaning that there is an uneven distribution of electron density.
Water has a partial negative charge ( ) near the oxygen atom due the unshared pairs of electrons, and partial positive charges ( ) near the hydrogen atoms. Furthermore, An
ethanol molecule is about 4 × 10-8 m across, while a
water molecule is only 1.7 × 10-8 m across.
Yes Fusel's are a problem I have yet to rectify completely. However, in regard to the thread I had mentioned addressing freeze distillation/reducing/concentrating to produce a higher ABV, the Fusel's are there even without distillation. Fusel alcohols are higher order (more than two carbons)
alcohols formed by
fermentation and present in
cider,
mead,
beer,
wine, and
spirits to varying degrees. Excessive concentrations of these fractions can cause off flavors, sometimes described as "spicy," "hot," or "solvent-like." Some beverages, such as
whiskey,
Siwucha and traditional
ales and
ciders, are expected to have relatively high concentrations of fusel alcohols as
part of the flavor profile. Here we can see that fusel's are not always the bad guy. But in other beverages, such as
vodka and
lagers, notable presence of fusel alcohols is considered a fault. Very high concentrations - usually caused by incompetent distillation or improper fermentation - can cause illness, including headaches, nausea, vomiting, clinical depression, or coma. Such a liquor may be referred to as rot-gut or rotgut. Fusel alcohols are formed when fermentation occurs: at higher temperatures ( when ethanol combines with esters,
fusel alcohols in beer are formed. These are the longer chain alcohols that get produced when fermenting at higher temperatures, therefore fermenting at a lower temperature for a longer period of time will form less Fusel Oils), at lower
pH, and when
yeast activity is limited by low nitrogen content. There are ways to address this: ferment at the lower end of the temperature range for the yeast selected, switch yeast if lower temperatures still produce unacceptable levels of “hot” fusel alcohols, examine your nutrient additions and oxygenation procedures to make sure the yeast are happy and health, sometimes it is best to
introduce some extra sugar later on in the fermentation. This is called Chaptalization. When adding Belgian Candi sugar to your stronger Belgian ales, some homebrewers recommend adding it a few days into the fermentation so the yeast are past the lag phase and hard at work. Too much sugar in the wort can stress the yeast and make it difficult for them to uptake the nutrients they need to multiply and form strong cell walls. It is always best to baby your high alcohol beers through the fermentation with plenty of attention to temperature, nutrients, and oxygen. The actual makeup of fusel oil depends principally on the ingredients of the fermentation, the fermentation temperature, and to a lesser extent the Fermentation variables like pH and Nutrients. The addition of ammonium salts to a Fermentation reduces the formation of fusel oil. Although, Fusel oil is the aroma of the mash. As opposed to the fermentation process, during
distillation, fusel alcohols are concentrated in the "
tails" at the end of the distillation run. They have an oily consistency, which is noticeable to the distiller, hence the other name fusel oil. A high percentage of Fusel oils can lead to
Chill Haze or louching. This is typical of several styles of spirits, including
Ouzo and
Absinthe. Here I am not suggesting this as an alternative to a quest for
the perfect "neutral" , but more an alternative to breaking the law to obtain a fortified solution.
As for the head fractions, this is very simple. After fermentation heat the wort to 169 F/77 C, hold it at temp for 10-15 minutes and the heads will remove themselves. Then cut the heat and cool quickly if possible. You will be surprised at the clarity your flavors will retain, and the removal of methanol/heads seriously benefits your outcome.