REDUCTION, SULFATES & LIGHTSTRIKE

BY TIFFANEY AND MACKENZIE

GWS 410 ~ FALL

REDUCTIONAn oxidized compound that gains an oxygen atom and loses an electron because it to becomes reduced when it gains another electron.

REDUCTION

Oxidation-Reduction (Redox Potential)

• The potential of the wine to hold its oxygen atoms

• Is an exchange of electrons and oxygen between the atoms

• Process happens in stages • How smelly sulfur compounds get in the wine

REDUCTIVE ENVIRONMENT

Low Redox Potential

• Allows reduced sulfur compounds to develop

• Is effected by (HIGH) pH levels

• Leads to stinky wines

High Redox Potential

• Will precipitate out and has a better hold on oxygen

• pH levels are low

SULFUR

Important for the fermentation process while also being byproduct

Non-mental Element in 2 amino acids created when yeast cells absorb sulfur:

Cysteine and Methionine

Yeast utilize it in the juice (and fermentation) to produce Hydrogen Sulfide (H2S)

SULFUR

LIGHT

• Low perception threshold

• Happens during fermentation and/or aging

• Use of aeration, sparging, and copper can be used

• Usually >1ppm

HEAVY

• High perception threshold

• Happens during yeast metabolism during fermentation not after

• Big problem: cant use aeration or copper

• 50-1200ppm

SO2

Sulfur Dioxide (Sulfites)

• Used by winemakers

Binds with aldehydes to “stable” and preserve the wine

Smells: Matchstick

Sensory: 66ppm in white wine

100ppm burns the nose

150ppm is undrinkable

SO22 Primary actions:

• anti microbial agent

• anti oxidant

-For white wines added before fermentation and added after to stop malolactic fermentation

-For reds to stabilize color before fermentation

Also capable of taking on another oxygen atom to become S03

S02 has the capability when combined with H20 to become

Sulfuric Acid

S02 + H20 = H2S04

S04Byproduct of plant and animal decay

H2S

Hydrogen Sulfide

• Needs yeast cells that are nitrogen starved to increase

• Light sulfur compound

If in the wine it is not noticeable early on, but can be fixed with SO2 or splash racking if caught early on.

Smells: Rotten Egg

Sensory: 1ppb

MERCAPTANS

Also known as: Thiols

Result from the reaction of H2S with alcohol or amino acid sulfurs

• Do not aerate

• Cure with copper sulfate

Smell: Cabbage, Rubber, Garlic, (at worst) sewer gas.

Wines that have had excessive exposure to ultraviolet light.

- Delicate varietal wines like Champagne are especially perceptive to lightstrike.

- Red wines are rarely affected due to the phenolic compounds present within wine that protect it.

Caused by sulfur containing amino acids that react with naturally occurring vitamins that are destroyed by UV light. This reaction creates smells and tastes.

LIGHTSTRIKE

Fault causes: aromas and tastes of wet cardboard, wet wool, rotten egg and vegetal smells.

Prevented by:

• -Bottling in dark bottles• -Storing wine in dark places

In France lightstrike is known as "goût de lumière", which translates to a taste of light.

LIGHTSTRIKE

Blocks 90% of UV Rays

LIGHTSTRIKE

Blocks 50% of UV Rays

Blocks 10% of UV Rays

* Can differ depending on thickness of glass, label placement and intensity and angle of light source.

Where does lightstrike happen most?

- Stores that use florescent lighting

- Display Cases- Refrigerators

How to avoid it:

- Look for dark glass bottles- Don’t pick bottles from top shelves

- Avoid window and refrigerator displays.

LIGHTSTRIKE

3 THINGS TO REMEMBER

1. What wines does Lightstrike affect and how can you prevent it?

Lightstrike affects white wines and rarely red wines. It is prevented by using dark glass for wine bottles and storing bottles in dark places.

2. What are the two amino acids produced when yeast cells absorb sulfates?

cysteine and methionine

3. What are three identifying smells for reduction?

ie: rotten eggs, rubber, burnt matchstick

ANY QUESTIONS?