Evaporating Boundaries: The Role of Rotary Evaporators in Gastronomy and Mixology

Welcome back to the evaporation corner of the ‘Colorful Researchers’ blog. So far, this blog has focused on the physical aspects of the rotary evaporator and how to integrate and maintain them in your lab. However, today, I would like to discuss how the rotary evaporator is used with a focus on more modern applications in gastronomy and mixology settings. Many of the top bars and restaurants worldwide have turned to science to elevate their craft, and the rotary evaporator has found a home in a number of these establishments. So, prepare to tickle your tastebuds and evaporate your expectations as we discover how chefs can make pasta transparent and how mixologists can clarify a cloudy cocktail.

What features make rotary evaporation special?

The rotary evaporator has two special tricks that enable a gentle yet efficient distillation, which other methods cannot achieve.

First, it places the mixture under a vacuum, lowering the boiling point. This eliminates the need for high temperatures that could alter or damage the product.

Second, the evaporating flask rotates while being immersed in a water bath. This rotation increases the sample’s surface area, accelerating the distillation process through forced convection. The mixture is evenly heated and mixed, promoting stable and even evaporation.

What are the common uses of rotary evaporators?

These unique features have found numerous applications over the years, making the Rotavapor^® a staple in chemistry labs worldwide. They are commonly used for:

Solvent Removal
Purification
Extraction
Synthesis
Solvent Recycling
Sample Preparation
Handling Heat-Sensitive Compounds

It was only a matter of time before chefs and bartenders realized how the rotary evaporator could assist their professions. Recently, I had the pleasure of visiting the Jerry Thomas speakeasy in Rome, where a group of passionate bartenders have been pushing the boundaries of mixology. The bar seamlessly blends the past and present by bringing back forgotten flavors and reimagining timeless classics. Many of their signature cocktails rely on using Buchi Rotavapors^® to achieve the uniqueness that has led to the speakeasy making it onto the list of the “50 world’s best bars”. I highly recommend paying a visit if you ever find yourself in Rome; you’ll be hard-pressed to find a cocktail containing Genever, Doragrossa, Caffè, Beer EDV, Ponzu, Shitake, and Koji Coffee anywhere else!

How are rotary evaporators used for gastronomy and mixology?

Chefs and mixologists are obsessed with the senses, how things look, smell, and taste. The rotary evaporator helps in all these areas by concentrating flavors, extracting volatile aromas, and preserving delicate flavors. This is where the vacuum and rotation come to the rescue. Take mint, for example; if you were to extract the flavor of mint using traditional boiling methods, the mint would turn black and taste bitter. This happens because the high temperatures break down the delicate compounds responsible for the mint’s fresh flavor and aroma, leading to oxidation and degradation. Using a rotary evaporator reduces the boiling point and prevents thermal degradation, allowing you to extract the essential oils and flavor compounds, preserving the mint’s natural flavor.

What are you extracting to obtain flavor when using a rotary evaporator?

Numerous aromatic compounds influence the taste and aroma of your final product, including:

Esters – formed during alcoholic fermentation via yeast metabolism, these aromatic compounds are the main class of flavour compounds in distillates. Specific examples include ethyl acetate (fruit), phenethyl acetate (flower), benzaldehyde (almond), ethyl lactate (butter-dairy-malolactic fermentation)
Terpenes – primary constituents of essential oils and many types of plants and flowers. Essential oils are widely used as fragrances in perfumery and traditional medicine; these produce limonene (orange) and nerol (sweet rose) odors
Alcohols – for aroma; examples include benzyl alcohol (almond), ethyl maltol (cooked fruit), furaneol (strawberry), menthol (peppermint), etc.
Aldehydes – such as acetaldehyde (pungent), benzaldehyde (marzipan, almond), hexanal (green, grassy), cinnamaldehyde (cinnamon, citral (lemongrass, lemon oil), hexenal (green tomatoes), neral (citrus, lemongrass), vanillin (vanilla).
Amines – such as cadaverine (rotting flesh), Indole (jasmine flowery), putrescine (rotting flesh), pyridine (very unpleasant), trimethylamine (fish)
Ketones – such as octenone for a blood, metallic, mushroom-like aroma effect, acetyl pyrroline for bread and jasmine odor, and acetyl tetrahydropyridine for fresh bread, popcorn odor.
Lactones – for a sweet coconut odor

What are the key considerations for chefs and mixologists using rotary evaporators?

Safety:

The primary concern for chefs and mixologists is safety. Humans will consume the products of your distillations; therefore, safety is paramount. As mentioned, Rotavapors^® are generally used in chemistry labs, so if you have acquired a second-hand rotavapor, you need to know if it has been used with potentially lethal chemicals. If you are unsure, you should replace the glassware immediately.
The process of distillation will change the properties of the product being distilled and could pose health risks. For example, distilling absinthe is not recommended as it is traditionally made with wormwood (Artemisia absinthium), which contains the ketone thujone, a compound that can be toxic in high concentrations. It is important to understand the properties of any ingredients you intend to distill.

Tips:

For culinary and mixology processes, using a beaker flask may be advantageous. A beaker flask has a much wider opening than an evaporating flask, which makes it easier to add and remove your product and helps when cleaning the accessory.
Natural products tend to foam during distillation. This causes bubbles to travel through the system and into the condenser, where they will be difficult to clean. A foam sensor is recommended. It senses when the foam is created, automatically breaks the vacuum, and aerates the system, preventing formation.

System Settings:

A certain amount of trial and error will be involved to perfect your processes, but a great place to start would be the ‘Solvent Library.’ In the interface settings of BUCHI Rotavapors^®, you can find the solvent library that lists the common solvents used. Many of these are for chemistry applications and would not apply to gastronomy and mixology. For these applications, the most important are water and ethanol. Once you have chosen the desired solvent, the system automatically sets the temperature and pressure settings for an efficient distillation. These serve as a great starting point for further optimization.

Now you know the basics, I’d like to leave you with a mixology application from our friends at Jerry Thomas. Be sure to check out our webinar with one of their master mixologists, who discusses how they use our Rotavapors for their daily distillations.

The following application shows how they reimagined the classic ‘Old Fashioned’ cocktail by clarifying the ingredients using a rotavapor, creating a crystal-clear liquid that maintains the heady taste of the original cocktail, making it a feast for the eyes, nose, and mouth!

Old Fashioned Clarified:

Set your rotary evaporator as follows:
Thermal bath: 52 °C
Chiller: 5 °C
Vacuum: 80 mbar
Pour 1.308 g of bourbon whiskey into an evaporation flask.
Evaporate the solution for 40 minutes at 80 mbar.
Lower the pressure to 60 mbar and evaporate the solution for 10 minutes.
Lower the pressure to 55 mbar and continue the distillation process until a solution with an alcoholic strength of 72 abv is obtained.
Stabilize the solution with demineralized water until it has an ethanol content of 45%.
Store in an airtight container for 24 hours before use.
Settings may have to be adapted to account for the specific bourbon/ whisky you use.
Zero Waste: Once the clarified bourbon has been made, the remaining sample can be used to create a non-alcoholic bourbon by adding sugar (it can be used for drink or food applications).

Uf Widerluägä,
Peter