Steam, direct fire, bain-marie: the Grappa distillation techniques
The alphabet was invented in 1800 BC, while ancient mortar came one millennium earlier: these two elements mark the dawn of civilization. The alembic still? It was known in Central Europe 6,000 years ago and was already used in Mesopotamia in 3500 BC.
In 2015, archaeologist John Bartholomew reconstructed a still by imitating the one found in Central Europe, which dates back to 4000 BC. He even used it, obtaining good results: humanity had not yet developed phonetic writing nor created an essential building material, but was already well-versed with spirits.
Read our entry on the ancestral history of distillation
Distillation is not equivalent to boiling (which can be done with just any container). Distillation is an extractive process: the heated liquid gradually releases different substances through evaporation. By controlling the temperature, these substances can be separated and then collected. The key to distillation lies in the correct distribution of heat because the various components contained in the raw materials (the pomace, for grappa) evaporate in different conditions.
Industrial grappa vs artisanal grappa
Technology has evolved over time. Since the 19th century, innovation has paved the way to industrial continuous distillation which allows the extraction of large quantities of alcohol in a short time. The resulting distillates are very clean but characterized by standard aromas. Today, some machineries can “disalcolate” (which means separating the pomace from its volatile components such as alcohol and aromatic substances) 5,000 quintals of pomace in 24 hours. The process allows to considerably reduce costs, but the quality of the resulting grappa cannot match with those obtained through slower and more delicate methods.
Some artisanal distilleries like Marolo propose traditional distillation methods. By combining modern technologies and pre-industrial techniques, they have contributed to the renaissance of an expertly handmade distillate. These techniques may be slower and less “productive”, but they highly respect the raw material.
STEAM, DIRECT FIRE AND BAIN-MARIE
Artisanal distilleries mainly use three methods for heating alembic stills.
1. Direct fire
This is the most ancient method: heat is distributed directly under the combustion chamber where the pomace is placed. This is a simple yet highly effective method, but it must be carried out with utmost attention. Fire could excessively “burn” the pomace, just like a pot that was left unattended over fire. Great experience and knowledge are therefore required for the distillation process to only capture the «heart» of the grappa, which is made up of alcohol and noble components.
Read our entry What’s in grappa?
This is the most common technique, also used by industrial grappa producers: at present, more than 90% of Italian grappa is made using steam distillation. The process makes use of hot steam created in a separate boiler: steam passes through the pomace (contained in the combustion chamber) and enables the evaporation of alcohol and aromatic components. This technique allows to easily manage each step of the process and respect the raw material, since steam reduces the boiling point of the pomace’s components.
is Bain-marie distillation is an ancient technique which provides that the combustion chamber does not come in direct contact with the source of heat. The boiler has two walls divided by a gap where steam or boiling water circulates. This method ensures that the pomace inside the boiler heats up and allows the evaporation of alcohol, fatty components and aromatic substances, which will make up the future grappa. Bain-marie distillation is definitely a much slower, progressive and delicate method compared to the previous ones: since the pomace does not come in direct contact with heat nor is it permeated by steam, the raw material completely respected, and its characteristics are maintained in the final grappa.
Grappa produced through bain-marie distillation is distinguished by a round, subtle and well-balanced aromatic profile. The final product presents delicate fruity and floral aromas, which are unstable when heated and are therefore usually lost due to the high temperatures of the boiler.
Marolo makes use of bain-marie distillation to produce its grappas, obtaining high-quality distillates that aim to preserve the identity of the pomace of origin.