Is calcium involved in taste transfer?

New research into the mysterious domain of taste by a US
neuroscientist suggests that calcium plays a key role in the
detection of tastes by taste cells in the tongue.

University of southern California (USC) researcher Emily Liman opted to investigate taste buds - made up of bundles of 50 to 100 taste cells - to better understand how animals detect sweet, bitter and umami flavours.

Her findings, published in the 1 December issue of Proceedings of the National Academy of Sciences​.

Until recently, scientists have known little about how taste works on a cellular or molecular level. Just four years ago, scientists officially added the taste umami to the list of the better known: sweet, bitter, salty and sour.

Umami receptors are sensitive to the amino acid glutamate, used in the commonly used flavour additive monosodium glutamate, which scientists believe serves as a marker for protein-rich foods.

Food and drug industry scientists also are interested in understanding the molecular details of taste, especially bitter and sweet, Liman said.

"It's important to know how taste works and to identify the molecules involved,"​ she added. "These molecules can be targets for designing chemicals that activate taste - for example, a better artificial sweetener - or that block taste, such as an additive that could be used to block bitter tastes."

In the study, Liman and collegue Dan Liu looked closely at a protein necessary for detecting sweet, bitter and umami tastes. Without the protein, called TRPM5, mice can not discern between the flavours.

Once activated, the protein appears to play a key role in the taste-signaling pathway, somehow sending a message to the brain about what's been tasted.

Liman, who has investigated similar issues relating to the sense of smell and pheromone detection, studied how this protein worked in an experimental cell system.

She found that the protein acts like a gated bridge on the cell's membrane, connecting the inside and outside of the cell. The gate opened when the researchers added calcium ions.

The researchers further found that the TRPM5 protein gate opens up again through an interaction with another cellular molecule called PIP2. Liman cautioned that her team has yet to show conclusively that calcium is responsible for the initiation of the signal to the brain.

In order to prove this, she will have to see whether her laboratory studies apply to taste cells in living animals, experiments she hopes to start soon.

Related topics Dairy-based ingredients

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