Thermal Amplitude

We've written about thermal amplitude in the past.  It's basically the same thing as the diurnal shift, the difference in temperature between daytime and nighttime.  The greater the temperature difference, the better the fruit.  Today's post was prompted by seeing the thermal amplitude wording on the back label of Puramun's Co-Fermented Malbec/Petite Verdot blend.  

Puramun is a prestigious label from Pepe Gallante of the Valle de Uco of Mendoza, Argentina.  For this wine the two grape types are hand harvested and then fermented together, a process they think brings out more of the great Malbec character.  The wine then sees twelve months in oak.

Valle de Uco is a special place within the larger special place of Mendoza, one of the truly great wine venues of the world.  Mendoza is the huge plateau in the middle of Argentina that has received financial investment from many of the greatest international wine companies.  It is a high altitude, sandy soil environment that has never seen the phylloxera problem other wine regions have been plagued with because of those conditions.  Apparently the plant louse behind the problem doesn't care for high altitude sandy soils.

The subject of thermal amplitude was clearly explained in a blogpost by APU Winery: Daytime photosynthesis creates energy and stores carbohydrates (glucose) while at the same time plant respiration converts nutrients from the soil into energy for internal cellular activities.  At nighttime when less energy is needed respiration slows with the colder temperatures.  The leftover energy from the daytime activities is then directed to the fruit which develops rich intense flavors, color and acidity.  If the daytime heat is sufficient, the grapes ripen faster, developing darker fruit flavors and thicker skins for desirable tannins. 

And there you have it.