Abstract / Synopsis:
Cannabis analysis over the past decade has progressed from non-existent idea to an evolving daily practice. The initial targets for analysis were the cannabinoids in order to determine the psychoactive compound concentrations in the cannabis products. Now, the field is expanding to encompass other important target compounds and elements. Certainly, compounds like pesticides and elements such as heavy metals are of particular importance to health and safety of consumer products. But, there are thousands of other potential analytical targets in cannabis which are still relatively unexplored. These compounds contribute to the health, nutritional, and more esoteric aspects of cannabis such as flavor, scent and overall composition.
Many chemical compounds can be responsible for scent and flavor in botanicals. Taste and smell are two of our primary sensory systems in which humans perceive the world. Both taste and smell are chemoreceptive senses meaning that there are specialized sensory receptor cells that convert a chemical substance to a signal such as neurotransmitter or an action potential in a nerve cell. There are two types of chemoreceptors: distance and direct. Distance chemoreceptors are present in the olfactory system (smell) and allow the detection of chemicals in a vapor or gaseous state. These receptors allow for the detection of odors and pheromones. Direct chemoreceptors are present in the gustatory system (taste).
Chemical compounds interact with chemoreceptors in the mouth or nose and create a response. In human beings, the tongue is the most important sensory organ for taste but there are chemoreceptors all over the mouth. Salivary glands in the mouth produce saliva, which is a chemical cocktail of water, electrolytes, cells and enzymes. The saliva is also a liquid or aqueous matrix for the food to interact with the taste buds as well as begin digestion of starches and fats. Without the assistance of saliva, the taste buds would not be able to chemically interact fully with the various flavors of food.
The chemoreceptors of the tongue and nose are primarily G protein-coupled receptors (GPCR). In addition to the GPCRs, the tongue also contains channels. GPCRs in the mouth are proteins that bind to ligands and begin signaling action potentials within the brain to differential between the three of the five basic tastes: sweet, bitter, and umami (savory). The taste of sour and salty are perceived through ion channels which are pores in membrane proteins that allow ions to pass into cells and through membranes. These chemoreceptors are located in taste buds around the mouth and on the tongue.
Each taste is triggered by different groups of compounds and different mechanisms of action. (See Table I above). Sweet tastes are triggered by compounds such as carbohydrates and carbonyls activating GPCRs on the front section of the tongue, while salty tastes are triggered by alkali metals via ion channels set just behind the sweet areas of the tongue. These chemical reactions are transformed into neural impulses and travel along the various facial and major nerves to centers in the brain which then interpret the impulses and create taste perception. Impulses sent to the somatosensory and frontal cortex of the brain are perceived as a conscious understanding of taste, while impulses sent to the amygdala and hypothalamus perceive an emotional context of taste. Finally, the hippocampus gives us the memories of taste. These perceptions of taste along with the mouth feel of food or texture, the olfactory impulses associated with smell and the sensation associated with temperature, pain and pressure (chemesthesis) combine to create the impressions of flavor.
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Patricia Atkins is a Senior Applications Scientist with SPEX CertiPrep and a member of both the AOAC and ASTM committees for cannabis.
How to Cite This Article
P. Atkins, Cannabis Science and Technology 2(3), 22-27 (2019)