GOOD GUY DISTILLERS W RITTEN A N D P H OTOGRA P H E D B Y D AV I D L E T T E N E Y
THERMAL OIL DISTILLATION VS STEAM DISTILLATION T
here are many factors that influence the character of single malt whiskey. Barley varietal and malting style, mashing and fermentation factors, water, still type, cut points, and maturation are just a few. One often overlooked and critical factor is the heating and temperature of the still when distilling. Beginning in the early 1500s, distilled spirits made in Scotland were traditionally produced on stills heated by open fire. This method of heating was used for hundreds of years until the late 20th century, when many of the Scotch distilleries converted their heat sources to steam. There are many advantages to using steam for heating distillation. The efficiency of heat recovery and regeneration is maximized, and the explosive concerns of using open fire to heat ethanol is mitigated. The majority of steam boilers being used have a maximum temperature of 135 degrees Celsius. This temperature is more than sufficient to boil wort for distilling, making it an obvious draw, but there is much more to distillation than merely boiling wort. There are many complex reactions that occur simultaneously with distillation. For the first distillation, wort containing significant W W W . ARTISANSPIRITMAG . C O M
amounts of unfermented sugars is heated in a pot still. When sugars are heated, caramelization and Maillard reactions take place. Maillard reactions happen when an amino acid and a reducing sugar combine in the presence of heat to form a wide variety of non-enzymatic browning reaction products. These reactions are responsible for non-enzymatic browning, which is why a seared steak is brown, or a cookie fresh out of the oven is darker. Some of the classes of compounds that are created from Maillard reactions are pyrazines, pyrans, and furans. These compounds have nutty, coffee, roasted, and caramel aromas and flavors associated with them. Maillard reactions require a minimum temperature of 140 degrees Celsius. Caramelization reactions produce similar compounds (furans) via the oxidation of sugars that are present in the wort. Different sugars undergo caramelization reactions at different temperatures. Above 110 degrees Celsius, fructose begins to caramelize, while glucose and galactose require 160 degrees Celsius and maltose not until 180 degrees Celsius. The products of Maillard and caramelization reactions are a sign of quality and complexity
In a thermal oil system, thermal oil is heated and run through an external calandria heat exchanger to heat the wash for distillation. in the single malt market. If Maillard reactions don’t begin until 140 degrees, and most of the caramelization happens above 160 degrees Celsius, does this mean the future of Scotch whisky is going to be devoid of these complex and delicious characters? To combat this problem, a thermal oil heating system was designed and built, by Briggs of Burton Engineering Firm, for Bently Heritage. Instead of using steam or direct fire for the heating of the stills, a thermal oil system was implemented. In this system, thermal oil is heated and run through an external 31