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SIDEBAR 2 coarse dispersed solids such as crystalline Two Flocs in Whisky:
on WHISKIES, precipitates, metallic turbidity, and the
COLLOIDS, charcoal particulates from the barrel char “Reversible” and “Non-
(Discher, 2016). In the next (“cosmetic”, Reversible Floc”
FATTY ACIDS, optional) filtration step, ethereal, oily Aylott (2014), in a discussion regarding
STEROIDS and fatty compounds are separated out at whisky analysis, cogently covers whisky
and CHILL- low temperature — chill haze component stability in a mere one-page sub-headed
PROOFING removal! [See SIDEBAR 2.] topic. “Filtered whisky is normally a clear
product, but two forms of flocculation may
Visible hazes or turbidities are also, as
Whiskies and other aged spirits are, as implied earlier, caused by mineral-laden occasionally be experienced in Scotch
discussed in the main text, subject to the dilution water. In practice dilution water whisky.” (Aylott, 2014). The first described
physical and chemical principles related should be as pure and free of calcium, is known as “reversible floc” and may form on
to colloidal stability and the production of magnesium, silicates and iron as possible. long term storage at very cold temperatures.
colloidal particles (see also SIDEBAR 1: on It is suggested than bourbon whiskey [There is a tendency in the US for consumers
COLLOIDAL STABILITY and HAZES).
Grain based spirits may see the contribution containing as little as 1 part per million of to store spirits in the freezer and this is one
of lipids via extraction from the barley or calcium will show some precipitation given reason we are seeing more samples with
other cereals and these carry through all the sufficient time (personal communication precipitation-related issues.] The whisky
processes and to the maturation phases. Other from a Kentucky bourbon distiller). When develops a haze which disappears upon
lipid class molecules – the sterols are derived warming and shaking of the spirit; the haze
from the wood and are related to the largest choosing, or using, filtration media the
class of plant derived chemicals known as distiller must be sure these too are low in or clouding here was referred to as “greying”
the terpenoids. More on the structure and calcium, magnesium and iron, otherwise in the earlier literature. When such hazes are
chemistry of these constituents is presented these very filtration systems will impact the examined the culprits are found to be ethyl
below, following a general discussion on stability of the filtrate and precipitation and esters of long chain fatty acids and larger
colloids, lipids and cold or chill-proofing of alkyl esters. [See SIDEBAR 2]
spirits. turbidities will arise later. The application
The Scottish whisky industry is known for of filtration processes should, therefore, The “reversible floc” formation can be
the use of the chill filtration process to reduce not be considered lightly nor essential minimized via chill filtration. Some craft
the propensity for chill haze formation. This to a particular operation without careful distillers say categorically no to filtration
will apply to bourbon whiskey production thought. Issues arising from filtration of and as such may have to live with the
also and the method is proposed for rums “problem” or state “this product may show
too as detailed within the main text. When spirits was dealt with in the early literature,
whiskies are above 46% ABV - at around and processes implemented to otherwise a precipitation upon cooling” and that it is
20-25 °C - no hazes or major effects on clarity ensure clarity and stability of product when harmless enough in nature. However, we
will usually be evident. However, and for filtration itself indeed caused issues beyond are seeing cases where the entire bottle
example when reducing aged spirit to bottling its desired intent. shows these floating masses that have been
strength the spirit may become cloudy (hazy),
reducing its visual appeal to the consumer. called “snow globes” by some brewers and
Based on the actual composition different Key papers from the 1960’s distillers based on their distinct appearance.
whiskies will also have different levels of lipids As stated earlier, very little has been Aylott states, “This process (chill filtering)
and so some will show the issue of chill-haze published (at least in English) on the topic reduces the concentration of “reversible
or clouding more intensely and/or more often floc” forming material and has no effect
than others. of turbidity and sediments. The reader
The chemical explanation for the should, therefore, be aware of three key on product character.” Refer to the details
appearance and disappearance of cloudiness papers from the 1960’s (Warwicker, 1960; cited from Discher (2016) under Causes of
in spirits such as whisky is related to hydrogen 1963 a, b). While not easy reading, many Turbidity and Filtration above for more on
bonding and to so called hydrophilic (water this.
loving) and hydrophobic (water hating) points, also presented and summarized here The second form of flocculation is known
properties of water, ethanol and lipids. Lipids in this article, can be uncovered from the
(from the “fat” class of molecules) consist of description of the extensive experimental as “irreversible floc” and presents as hair-
a portion known as the head and a portion work carried out under the direction of like crystals of calcium oxalate (see also
known as the tail. The head portion, which Warwicker. Some summary details are under TEQUILA, below). These crystals form
is hydrophilic – meaning it prefers to be in slowly and settle when the normally low parts
contact with like-minded molecules (those presented below. But first a little digression per million (ppm) concentrations of oxalic
that are water or water-like or loving) is — to floc or not to floc and what types of floc
characterized by an electrically charged — those are the questions now addressed. acid in the whisky react with also quite low
hydroxyl (OH) group. The tail group which See below and both SIDEBARS 1 and 2 for concentrations of calcium ions. Hence the
hates water (water fearing = hydrophobic) extended details. need to keep calcium to zero (or absolute
is composed of one to three variable length minimum) levels in dilution water. Some
hydrocarbon chains. See Figure 1 for typical distillers will also remove some of the oxalate
structures of phospholipids and steroids.
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