Thermal Treatment of Wine Grapes:

Laccase Denaturation and

Sensory Defect RemovalFlavor 101A-Recognizing Off Flavors

UC Davis09 December 2011

Rick JonesConsulting Winemaker

Della Toffola USA

The Goal is Simple:

Permanently deactivate laccase by heat denaturation of the protein.

But there’s a catch…you must heat to very high temperature (greater than 150 F) RAPIDLY or you can make things worse!

Why?

Enzyme Activity Increases with Temperature

Effect of Temperature

0

50

100

150

200

250

10 20 30 40 50 60 70 80 90

Temperature (degree C)

Re

l. A

cti

vit

y

3 General Methods1. Classic Thermovinification

Heat to 140 F, hold for 2-12 hours, chill, press and ferment+ good color + inexpensive capital requirements- poor tannin extraction- energy intensive (need to heat and cool)- heating usually not fast enough for denaturation

2. Hot Maceration (MPC)Heat to 140 F, hold for 2-24 hours, chill, ferment on skins

+ For higher quality grapes - On Skins ferment can cause reintroduction of moldy character

3. ThermoFlash or Flash DetenteHeat quickly to 180F followed by immediate cooling in a vacuum chamber

+ good color AND tannin extraction+ ability to press off a balanced must immediately

to discard moldy skins+ complete laccase denaturation+ entrainment of moldy character in flash water

that can be discarded- expensive

The COOLER UNIT