COVER STORY

There was a time when we hap­pily thought the tongue could de­tect four more. MATT PRE­STON

Sunday Herald Sun - Stellar - - Contents - Ver­dict: proven – al­most.

The hunt is on for the elu­sive “sixth taste”. We look at the con­tenders.

Our per­cep­tion of taste has changed dra­mat­i­cally since the first ma­jor book about food was writ­ten in 1825. Jean An­thelme Bril­latSavarin, a man with the rare hon­our of hav­ing a cheese named af­ter him, en­dorsed the idea of four tastes – sweet, salty, sour and bit­ter – in The Phys­i­ol­ogy Of Taste. To­day, we are dis­cov­er­ing this may be just the tip of the taste ice­berg.

Umami, first iden­ti­fied by Ja­panese sci­en­tist Kiku­nae Ikeda in 1908, is now widely ac­cepted as the fifth of the pri­mary tastes. It is the savouri­ness you de­tect in parme­san, toma­toes, Vegemite and fish sauce. But sci­en­tists aren’t stop­ping at five. A spate of con­tenders are vy­ing for the sixth taste spot. Es­sen­tial cri­te­ria: There are nu­mer­ous cri­te­ria sci­en­tists use to iden­tify when some­thing is a taste. Many con­tenders fail three of these check­points.

Firstly, the new taste must be uniquely dif­fer­ent from the other pri­mary tastes. Sec­ondly, it should trig­ger a bio­chem­i­cal re­ac­tion. Lastly, spe­cific re­cep­tors must be found to iden­tify the taste. So let’s as­sess each claimant’s case for the ti­tle…

Chilli heat or minty cool­ness: We cer­tainly know about these when they are in our mouths, but our abil­ity to dis­cern the tem­per­a­ture of food is ac­tu­ally a mat­ter of touch rather than taste – it’s a nerve re­ac­tion. The heat of chill­ies or pep­per, and the per­cep­tion of cool­ness with mint and men­thol, are chem­i­cals fool­ing our tem­per­a­ture sen­sors. Ver­dict: dis­missed. Astrin­gency: The mouth-puck­er­ing dry­ness you get from drink­ing stewed tea, sip­ping tan­nic red wine or eat­ing an un­ripe banana is astrin­gency. But that isn’t any­thing to do with your taste­buds. What’s hap­pen­ing is that the tan­nins cause the mu­cus mem­branes to con­tract, mak­ing this an­other me­chan­i­cal re­ac­tion. Ver­dict: dis­missed. Numb­ing: Both Sichuan and some In­done­sian cuisines use prickly ash berries, aka Sichuan pep­per, to give food a numb­ing qual­ity. Rather than a taste, this is an­other ex­am­ple of chemes­the­sis, in which the chem­i­cals in foods im­pact touch rather than taste. Ver­dict: dis­missed. Metal­lic: Some­times you get a metal­lic taste in your mouth, but this is caused by a re­ac­tion sim­i­lar to the way a bat­tery works. Elec­tri­cal im­pulses are picked up by the mouth as a taste, even though it isn’t one. Ver­dict: dis­missed. Cal­cium: There is a far bet­ter case to be made for the chalky or slightly bit­ter taste of cal­cium as the sixth sense. Sci­en­tists have found that mice have two taste re­cep­tors to de­tect cal­cium and one of those is found in hu­mans.

Fur­ther­ing the case for cal­cium is the sur­vival of the species. As taste de­vel­oped for hu­man preser­va­tion, bit­ter­ness and sour­ness were signs of harm­ful foods while sweet, salty and umami prom­ise some­thing we should eat for the car­bo­hy­drates, min­er­als or proteins. So the fact that cal­cium is es­sen­tial for hu­man life means the body had a good rea­son for de­vel­op­ing a way to iden­tify it. Ver­dict: jury is still out. Oleo­gus­tus: That’s fat to you and me. In 2015, sci­en­tists at Pur­due Uni­ver­sity, In­di­ana, claimed to have proved that fat is a pri­mary taste. The tricky part is that the rich creami­ness we taste and love is ac­tu­ally the feel of the fat, and when the taste can be iden­ti­fied it is a bit icky.

The fact that the ac­tual taste of fat was recorded as be­ing like ran­cid but­ter may mean our abil­ity to taste it is also a preser­va­tion tool sim­i­lar to pick­ing up bit­ter­ness. Ver­dict: proven – al­most. Starch­i­ness: Last year, a re­search team at the Uni­ver­sity of Ore­gon found that hu­man test sub­jects could taste the starch­i­ness that makes bread, rice and other carbs, which might ex­plain why we find pizza and pasta so de­sir­able.

The abil­ity to taste “glu­cose oligomers” was shown to be in­de­pen­dent of our abil­ity to taste “sweet” and now the re­searchers are try­ing to iden­tify the re­cep­tors on our tongues that pick up this floury flavour. Kokumi: Sci­en­tists who cham­pi­oned umami’s ac­cep­tance as the fifth taste are also keen to make kokumi the sixth.

They’ve been claim­ing since the ’80s that kokumi is that sen­sa­tion of rich­ness you taste with braised, aged or slow-cooked meats, scal­lops, onions and gar­lic. Oh, and with milt, but as you are un­likely to be a reg­u­lar con­sumer of fish sperm we can leave that one out.

But kokumi may just be part of umami and thus fail the “dis­tinct taste” cri­te­ria. Ver­dict: in­con­clu­sive. Car­bon diox­ide: This might be the most bizarre claim for the sixth taste, but the ev­i­dence is com­pelling. That zingy fizz when drink­ing car­bon­ated bev­er­ages was orig­i­nally thought to be a func­tion of touch – the feel of the bub­bles pop­ping on your tongue.

Back in 2009, re­search was pre­sented that mice could taste an en­zyme in CO₂. A sim­i­lar find came in hu­mans with a drug for al­ti­tude sick­ness which blocks the en­zyme. Climbers who have taken the drug re­port that once they pop a bot­tle of bub­bly to cel­e­brate reach­ing a sum­mit, the cham­pagne tastes flat. Ver­dict: proven, your hon­our.

As sci­en­tists con­tinue to un­ravel the com­plex se­crets of flavour, cal­cium, starch­i­ness and oleo­gus­tus are strong can­di­dates to be de­clared pri­mary tastes.

Prov­ing this be­comes in­creas­ingly com­plex as neu­ro­science asks ques­tions about the im­pact of mem­ory on taste, and the role of neu­rons that line our gut.

Un­til then, keep savour­ing food.

PASTA CRAVINGS If starch­i­ness is the so much. Net­tle spaghetti ca­cio e pepe. Recipe at de­li­cious.com. au.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.