Why A Strawberry Smells Like A Strawberry

Michael Harper for redOrbit.com — Your Universe Online

It´s easy enough to simply recognize that something smells like a strawberry, but it´s much more difficult to understand why something smells that way. Scientists from the Technische Universität München (TUM) set out to get to the bottom of the strawberry smell in order to understand a little more about scents and how our brains understand which scent and taste belong to which foods.

Though many people might describe a strawberry as smelling sweet or fruity, the TUM scientists have deduced that a strawberry´s aroma is actually the product of around one dozen different aroma compounds. One of these compounds is particularly important to the smell of a strawberry; it´s labeled with the brand name “Furaneol.” but it´s more scientifically known as HDMF (4-hydroxy-2,5-dimethyl-3(2H)-furanone).

Prof. Wilfried Schwab, head of Biotechnology of Natural Products at TUM has spent many hours researching the smell of strawberries to understand the biology of the HDMF compound.

“A ripe strawberry has a particularly high concentration of this compound — up to 50 milligrams per kilo — which lies far above the odor threshold. This compound gives the ripe fruit its characteristic caramel-like aroma,” explained Schwab in a statement.

HDMF isn´t only found in strawberries, of course. It can also be found in tomatoes and pineapples. According to Schwab´s research, HDMF can also be found in plants, though here the aroma develops in a different way as it moves away from the sweet sugar of the fructose.

The TUM team was more interested in understanding how HDMF converted in fruits, however, noting the process occurs when a molecule binds to the FaEO enzyme before turning into HDMF.

To understand this process and map it out in detail, the TUM aroma scientists turned to X-ray structural analysis of the molecules at play in this transformation. With these X-rays complete, Schwab and team compiled a 3D model which allowed them to see the specific structure of these molecules.

“For the strawberry aroma, we investigated altogether six different enzyme-molecule combinations — and ended up understanding how FaEO produces the HDMF flavor compound,” said Dr. André Schiefner from the Chair of Biological Chemistry.

As they were uncovering the source of the strawberry smell, the scientists uncovered a mechanism in the catalytic reaction which had yet to be observed. During this process, the compound is reduced then transferred to another part of the molecule. This, says the TUM scientists, means the FaEO is the first of a new class of biocatalysts. This strawberry-flavored research could lead to other applications and advancements in industrial biotechnology. Furthermore, Prof. Arne Skerra from the TUM Chair of Biological Chemistry says this research could help future scientists understand why some plants have a distinctive flavor.

“Unlike coffee or vanilla, the biochemical processes that produce the strawberry aroma are very complex. But now our TUM research team has shed light on an important step in its biosynthesis,” said Skerra.

In real world terms, this study could one day make it possible to recreate the true flavor of strawberries in cakes, ice cream, soda or yogurt. Though this research deals with the aroma of a strawberry, humans use scent to get a full picture of the taste of a food. With this process understood, scientists could one day make more realistic tasting food.

Results are published in The Journal of Biological Chemistry.