University of São Paulo: New barrel makes good cachaça: USP researchers study the aging of spirits

FORscholars from USP’s Luiz de Queiroz School of Agriculture (Esalq), in Piracicaba, studied the chemical and sensory aspects that influence the quality of cachaça aging in wooden barrels, a process that gives flavor to alcoholic spirits. The research shows that time is not a document when it comes to flavor: cachaças aged for five years in new barrels have a quality similar to those aged for 20 years in reused barrels. In other words, producers can save time and resources in the manufacture of a “young” product, which will provide a caipirinha as good to the consumer as if it were four times as “old”. “Everything is a matter of finding the sensorial balance”, says to Jornal da USP biotechnologist Mariana Costa de Castro, author of the study.

Aguardente, pinga, branquinha, marvada, catia are some of the Brazilian synonyms of the popular “cachaça”, which is nothing more than the result of the fermentation of garapa (sugar cane juice) – a time when sugar is mainly transformed in carbon dioxide and ethanol – and the distillation of this fermented, when it separates and concentrates what is of interest for consumption. According to data from the study, cachaça is second only to beer in the ranking of the Brazilian beverage market and ranks fourth in the list of most consumed alcoholic beverages in the world. But before reaching consumers, the product usually goes through the aging process.

Image courtesy of the researcher
Wooden barrels, or vats, have been used since the Middle Ages to store alcoholic beverages – and to age them and improve their flavor. The compounds called phenolics, extracted from the wood of the barrels in which the liquid is reserved, are responsible for chemically changing the composition of whiskey, rum or cachaça and modifying the alcoholic, aggressive, bitter and harsh flavor to something sweeter, smoother and private. This is a generally slow process, taking anywhere from three to more than 50 years – according to the survey.

Ethyl vanilate and ethyl syringe are examples of aromatic molecules that arise when the drink “rests”: they are the result of the interaction between wood macromolecules with alcohol and give the distillate a pepper, vanilla, floral, cherry, almond and spice flavor – this depends on the species of wood, the weather and the construction of the barrel.

Among the most common tree species in production, the oak ( Quercus genus ) is the most used, due to its favorable mechanical properties for cooperage. According to the study, the heartwood, the inner part of the trunk, is used, due to its ideal hardness and porosity. It undergoes drying, assembly and toasting, which gives the shape of the barrel, improves its aromatic properties and can be weak, medium or strong, depending on the burning time and flame intensity.

“Who wants to taste cachaça?”
To observe the influence of different factors on the cachaça aging process, the researchers studied, at Esalq’s Laboratory of Technology and Chemical Quality of Beverage (LTQB), cachaça aged for up to 60 months in new and reused oak barrels with medium toast and strong. The samples underwent physicochemical analysis, which assess the presence of aromatic compounds in the distillate, and sensory tests, which relate to flavor. For these tests, tasting sessions were necessary, but beforehand, it was necessary to find volunteers for the experiment.

“I had no difficulty finding volunteers,” jokes Mariana. The researcher went to an emporium, where various types of spirits were sold, and recruited 36 consumers to participate in the analysis. Some exclusion criteria were taken, such as being under 18 years old and not liking the product or consuming in excess. The tasting sessions also featured 12 subject matter experts; all took small doses and described on a qualitative and dot scale.

It could even look like a bar game, but in one of the stages, the tasters took doses from left to right and placed the glasses on a sheet of paper, bringing those they judged to be similar together and distancing those that were different. Then, they were instructed to write the characteristics of the cachaça on paper, according to their positions. The bad news for the volunteers was the advice not to ingest the samples. Data were tabulated by measuring the dose distances between each other and their descriptors by X and Y coordinates.

The coordinates of the positioning of the samples of each taster tabulated – Illustration by the researcher, adapted
“The 48 tasters had to judge the aged cachaça samples as similar or different. Statistical analysis was a way to compile all this information and transform them into easy-to-interpret graphs”, he explains.

A shot of science: “new” cachaça can have sensory complexity
The results showed that the strong toast favored the extraction and consequent evolution of aging compounds. According to the researcher, cachaça aged in oak barrels with greater toasting intensity or maturation time had a better sensory response. “The work allowed us to observe that factors such as wood species and degree of toasting can be worked on to more quickly increase the presence of chemical compounds found in more mature beverages, which allows us to compare the chemical quality of cachaça aged for five years with other aged spirits for 20 years”, he adds.

“The research resulted in a new methodology to determine the degree of aging in cachaça, no longer based on time [years] , but on the concentration of compounds extracted from the wood by cachaça and on the relationships between them”, says professor at Esalq André Ricardo Alcarde, research supervisor.

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