Flavors

Process flavors. When sugar is cooked it turns brown to generate a pleasant caramel odor, but if it is overheated it becomes black. For the industrial production of flavorants this raises questions such as

• how to improve the concentration of caramel odor?
• How can we match a kitchen heating profile in a 1 ton industrial reactor?
• How can we keep the flavors in powder forms?

I addressed these questions while studying the chemistry of commercially important food odorants. Most of this information was not published in the open literature but is proprietary. Flavors studied include: chicken, chocolate, caramel, roasted cereals and fried pork fat.

Screening natural products to find taste active compounds

The human mouth is similar to a bioreactor in which food is chewed in presence of enzymes and bacteria. Our mouth is also equipped with many sensors. Some are located in the nose, and these olfactory receptors are able to identify many odors, some a located directly in the mouth like the taste receptors, indicate if the food is sweet, salty, bitter, umami or even cooling or hot. Through my research, I explained for the first time that the particular taste of scallop, not sweet, not salty but not also truly umami. A world-wide field trip was undertaken to sample natural products in order to screen for active taste compounds. As a result of this investigation many spices were analyzed in the laboratoryand over 400 botanicals screened. We demonstrated the pungency differences in term of time intensity between different active compounds in spices.

Olfactory Perception of Sulfur Compound from Cysteine-S-conjugates

In my quest to determine the olfactory perception of sulfur compound from cysteine-S-conjugates my first major discovery was that enzymes from mouth bacteria release odorant molecules. this explained the retro-aromatic effect (odor released delay) in Sauvignon grapes, in onions and in bell peppers. The onion for example contains more than 90% of the cysteine conjugates with a sulfur atom bearing oxygen. These molecules are transformed in few seconds by plant enzymes when cells are broken, but non oxygenated cysteine conjugate remains and these compounds are transformed only by mouth bacteria enzymes. This explains why onion odor is persistent in the mouth. Nature exploits this strategy for example to keep animals scent markings. If for example cats only excreted the volatile sulfur compound, the odor will disappear rapidly, however excreting a cysteine conjugate named the felinine, makes the odor very persistent due its slow release. Many other examples exist, like glucuronides in human urine, glucosides in plants and glutamine conjugates in human body odors.