Bet­ter wine through chem­istry

Cosmos - - Special Feature -

Tas­ma­nian re­searchers are dig­ging down to the molec­u­lar level in search of ways to make bet­ter sparkling wine, faster. FIONA MCMIL­LAN reports.

Ev­ery time you open a bot­tle of sparkling wine, you are un­cork­ing a bit of mys­tery. There is still a lot we don’t know about the chem­istry of sparkling wine and how that chem­istry is achieved, ac­cord­ing to Fiona Ker­slake at the Univer­sity of Tas­ma­nia.

In a joint ven­ture funded by Wine Aus­tralia, she and her col­leagues at the Tas­ma­nian In­sti­tute of Agri­cul­ture have teamed up with wine­mak­ers to de­velop a way to an­a­lyse the chem­i­cal com­po­si­tion of sparkling wine more rapidly, and per­haps even to speed up pro­duc­tion.

The com­plex puz­zle be­gins on the vine, she ex­plains. Soil, cli­mate, ir­ri­ga­tion, fer­til­i­sa­tion and prun­ing each in­flu­ence the out­come, as do wine­mak­ing prac­tices from juice-ex­trac­tion tech­niques through to stor­age tem­per­a­ture.

How­ever, Ker­slake says: “Knowl­edge of the chem­istry of sparkling wines is quite limited, and so are the ways we can po­ten­tially an­a­lyse sparkling wines.”

In red wine, many im­por­tant chem­i­cal com­pounds are large and have colour, so they can be stud­ied by mea­sur­ing how the wine ab­sorbs vis­i­ble light. How­ever, many com­pounds in white and sparkling wines are smaller and colour­less, mak­ing them dif­fi­cult to ex­am­ine, Ker­slake says.

To ad­dress this, Ker­slake has been analysing juice des­tined for sparkling wine with vis­i­ble, in­frared and ul­tra­vi­o­let light. This process, done as the grapes are pressed, is let­ting wine mak­ers un­der­stand their wine at the molec­u­lar level.

Long mat­u­ra­tion times are also a chal­lenge for winer­ies rac­ing to keep up with high de­mand, says Ker­slake: “You have to be pretty pa­tient if you’re into sparkling wine.”

First, juice is fer­mented to cre­ate a still wine. Then yeast and sugar are added. As yeast con­sumes sugar, al­co­hol is pro­duced along with bub­ble-mak­ing car­bon diox­ide. But some­thing else is go­ing on, too.

Around three months af­ter this sec­ondary fer­men­ta­tion be­gins, the yeast cells be­gin to re­lease com­pounds as­so­ci­ated with de­sir­able flavours, such as toasty, nutty or sweet notes. This process usu­ally takes around 18 months.

Ker­slake won­dered if pre­emp­tively dam­ag­ing some of the yeast would trig­ger early re­lease of de­sir­able com­pounds.

To find out, she and PHD stu­dent Gail Gnoin­ski added dam­aged yeast to still wine, and pre­lim­i­nary re­sults sug­gest it is gain­ing the char­ac­ter­is­tics of slightly older wine.

Mean­while, they are also try­ing to fig­ure out ex­actly what hap­pens to yeast dur­ing fer­men­ta­tion.

“There’s a bit of a ques­tion around whether the yeast cells ac­tu­ally die or whether they just go to sleep or… leak,” says Ker­slake.

So Gnoin­ski is open­ing wine at dif­fer­ent stages and ex­am­in­ing the yeast un­der the mi­cro­scope. Her find­ings could re­veal which cel­lu­lar mech­a­nisms are ac­tive, and help to iden­tify the molec­u­lar path­ways re­spon­si­ble for a nice glass of bub­bly.

Science is help­ing wine mak­ers (and drinkers).

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