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SIDEBAR 1
the end of the day, careful attention to detail on COLLOIDAL
in producing spirits can prevent the occurrence STABILITY and HAZES
of particulate issues in the first place, and keep
customers and the distiller happy. A colloid is a homogeneous, non-crystalline substance consisting of large molecules or ultrami-
croscopic finely divided particles (1 to 1000 millimicrons [10-9 meter or nanometers] in size) of
Causes of Turbidity, one substance dispersed within a continuous medium in a manner that prevents them from being
filtered easily or settled rapidly. Colloids include gels, sols, and emulsions; the particles do not
and Filtration settle and cannot be separated out by ordinary filtering or centrifuging like those in a true suspen-
Discher, (2016) presents us with a sion. The term colloid also refers to the particulate matter so dispersed.
Colloids may be thought of as a mixture with properties between those of a solution and a fine
comprehensive listing of the causes of turbidity suspension (finely “floating” matter).
(hazes or colloidal suspensions) in whiskies
(See SIDEBAR 1: on COLLOIDAL STABILITY A colloidal gel is a colloid in a more solid form Much more is known or published on the col-
than a sol (liquid).
loidal stability of beer and, in this case, usually
and HAZE for general details and definitions on refers to the propensity of beer to form non-bi-
the topic of hazes and colloidal stability. Note: A sol is a colloidal suspension of very small ological hazes due to interactions between beer
solid particles in a continuous liquid medium.
the present article uses the terms hazes and Sols are quite stable and show a unique light components – principally polyphenols and
turbidity interchangeably as both are seen in the scattering pattern known as the Tyndall Effect. proteins leading to the formation of visible
literature). (The reader will find neat descriptions/demon- precipitates; colloids in beer can take the form
of gelatinous (jelly-like) masses. Sometimes the
The major causes of turbidity, accounting for strations on the web.) unidentified masses in spirits are opaque and
rankings of between 20-25% each, are: minerals A hydrogel is a colloidal gel in which water is gel-like in nature and maybe metal hydroxides
— calcium, magnesium and silicates; iron; and the dispersion medium. or other materials and are not usually based
polysaccharides — pectins (e.g., from wine- An emulsion is a colloid consisting of a mix- on proteins or polyphenols nor on associated
based spirits such as brandies, etc.) and dextrins ture of two liquids such as those of oil in water. protein-polyphenol complexes (Spedding, Lin-
ske and Weygandt, 2017). Though polyphenols
(short chain carbohydrates). Microorganisms and It refers to microscopic particles of liquid dis- and tannins are abundant in wood-aged wines
persed in another liquid. Milk is an example
higher fatty acids and fatty acid esters account whereby lipophilic (fat loving or hydrophobic and spirits! Further research work might be
for turbidity with rankings of around 15% each = water hating) particles are dispersed in a needed in regard to potential haze formation
(see SIDEBAR 2: on WHISKIES, COLLOIDS, water based (aqueous) medium (see SIDE- in certain distilled spirits even considering that
the rankings for polyphenols and proteins as
FATTY ACIDS, STEROIDS and CHILL-PROOFING BAR 2: on WHISKIES, COLLOIDS, FATTY causes of turbidity were illustrated as being
for more on fatty acids and sterol hazes). Less ACIDS, STEROIDS and CHILL-PROOF- low in the case of whiskies (Discher, 2016).
ING).
than 10% rankings for causes of turbidity then
Hazes are the result of light scattering by colloidal or larger particles suspended in the spirit
go to copper and polyphenols with other causes solution. Such hazes are usually visually unappealing and often signal to the consumer that some-
of lesser rank including; proteins, mechanical thing is wrong with the product. Most of the time these issues are caused by harmless materials
impurities, charcoal dust, dirt/debris — perhaps in the product arising from raw materials or from situations that arise during processing and or
from cardboard or other packaging materials and bottling (see main text). Given sufficient time most products will have a propensity to form some
filter fibers etc., the plant class of compounds form of haze or precipitates regardless as to the steps taken to ensure a long and stable shelf-life.
Particles of greater than colloidal size settle out if there is no agitation to suspend them or keep
known as terpenes, cork and, finally, higher them suspended. True colloids are indefinitely stable suspensions. They arise when the size of the
volatile sulfur compounds (Discher, 2016). particles is both sufficiently small and they are of density similar to that of the spirit – this keeps
The distiller has thus a clear need to them suspended (“floaties”) by Brownian motion (Siebert, 2006). [Brownian motion refers to
understand these many causes and the potential erratic random movements of microscopic particles in a disperse phase - particles in suspension.
remedies! A chart illustrating these causes and The movement is caused by continuous irregular bombardment of the particles by the molecules of
origin points might be drawn up by the distiller the surrounding medium.]
When a system is cooled, the withdrawal of energy can result in the settling of larger colloidal
as part of their quality assurance and quality particles and may cause solubility reduction and the formation of additional matter. Interestingly
control program. This list of causes appeared in the consumer often initiates this haze formation or precipitation by chilling the spirit in a very
a review dealing primarily with whiskies but, as cold fridge or the freezer. When the spirit is warmed up again or agitated the suspension disap-
will be seen, many apply to other spirit types as pears upon re-solubilization of the matter. A simple statement on the bottle to the effect of this
well. issue potentially happening might reduce the number of complaints over these visually unappeal-
ing though harmless “unidentified objects.”
The driving force behind the Discher paper is In addition to temperature, alcohol content and the solution pH exert strong influences on
to promote filtration to distillers but he covers precipitation and haze formation; this is discussed further in the text. The process of haze produc-
important concepts and origins of materials to tion is said to be reversible if no deposits have been produced and if the haze disappears when the
be removed by appropriate filtration. In dealing temperature is raised. If a deposit occurs the term “thick” may be applied and complete revers-
with whiskies, following dilution to bottling ibility is unlikely in such instances (Warwicker, 1960). Though as mentioned earlier, this topic is
quite complex based upon the number of components at play in distilled spirits production and
strength or blending, multiple and consecutive the spirit itself. This reversibility or irreversibility can easily be tested by the distiller with a few
filtration steps may be employed. Distillate simple experiments. Forced aging of bottled spirits could also be entertained to establish the shelf-
may be clarified via removal of fine colloidal to life stability of product. Simple visual inspections often sufficient evidence to show potential for
turbidity problems with product in the marketplace or consumer liquor cabinet.

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