The chemical allure of vanilla

Vanilla is a popular flavour but can be one of the most labour-intensive spices to produce, which can lead to shortcuts in the process resulting in a less tasty product.

Now, scientists have reported a profile of 20 key chemicals found in vanilla bean extracts, including several previously unknown ones, that together create vanilla’s complex and enjoyable flavour. The work could help manufacturers and farmers develop better-tasting vanilla and improve quick-curing methods.

The research findings were presented at the fall meeting of the American Chemical Society (ACS).

“Vanilla is the second-most expensive spice in the world,” said Diana Paola Forero-Arcila, PhD, who presented the work at the meeting. “One of the reasons it’s so expensive is because its flavour is developed during a curing process that takes up to nine months.”

Two shortcuts are currently used to get around this long, drawn-out curing process. One is to speed it up with quick-curing methods that attempt to recreate the natural vanilla flavour in a fraction of the time. Another is to make artificial vanilla as an alternative to the real thing.

These alternatives can fall flat in terms of flavour because they both focus on vanillin, Forero-Arcila explained. Quick curing attempts to maximise the amount of vanillin in the cured bean, whereas artificial vanilla contains only one flavouring agent — lab-made vanillin.

Although vanillin is an important part of a vanilla bean’s flavour, the alternative products can be missing the complexity of flavour. To capture that complexity, Forero-Arcila, who is a postdoc at The Ohio State University, used an approach called untargeted flavouromics to pinpoint which chemicals in vanilla bean extracts are the most important for the overall aroma and taste.

The researchers first made extracts from 15 beans they sourced from various countries and that were cured differently. They then constructed a chemical profile of each type of bean and identified which compounds were present. To find out how people reacted to the extracts, the team asked more than 100 individuals to taste the samples and rate whether they liked or disliked the flavours.

By connecting the dots between the chemical profiles and the taste ratings, the researchers identified 20 compounds that are the main drivers behind whether a person likes the flavour of a vanilla extract. Of these compounds, some, like vanillin, were expected. However, several compounds important for the flavour were completely unknown, said Devin Peterson, PhD, the project’s principal investigator.

The researchers are still analysing these novel vanilla compounds to determine the final structures, but they have observed that the compounds have phenolic and aglycone parts. They also identified some compounds present in the extracts that made people dislike the flavour. One example is anisaldehyde, which has a floral aroma. Forero-Arcila found that anisaldehyde is produced during the curing process from a previously unknown precursor.

Image credit: iStock.com/mesut zengin