Chapter 13 - General Winemaking Options Flashcards
Bad effects of O2
- Breaks down aroma compounds
- Turns white wines darker –> brown (phenolics in red wine have anti-oxidative effect)
- Creates unwanted products (acetaldehyde is the oxidation of ethanol that causes nutty apple aromas)
- Growth of spoilage organisms (brett, acetic acid bacteria)
How to avoid O2
- Ullage
- Cool constant temp
- Adding SO2
- Using impermeable vessels
- Using inert gases to flush O2 out of equipment
Good effects of O2 (6 things)
- Adds complexity
- Changes aromas and flavors for greater range and diversity
- Exposure to some O2 for white wine must increases oxidation stability
- Prevents reduction faults
- Needed to grow initial yeast population
- Required for reaction between anthocyanins and tannins for color stability
How to increase O2 exposure
- Racking
- Pump overs (cap management)
- Limiting SO2
- Using permeable vessels (barrels)
- Allowing ullage
- Using techniques that pump oxygen into the must (ie micro-oxygenation)
When are the best times to add SO2?
- Right after grapes are harvest
- Right when they arrive at the winery
- When grapes are crushed
- After malo
- Right before bottling
2 main purposes of SO2
Anti-microbial
anti-oxidant
Bound SO2 vs Free SO2
Bound SO2 - the portion that reacts with compounds in the liquid and are ineffective against oxidation and microbes
Free SO2 - unbound portion. Most exist in an inactive form. Some exist as molecular SO2 that is the most effective against oxidation and microbes
Why is adding too much sulfur bad?
- Reductive faults can occur (rotten eggs)
2. Can dull aromas and cause the wine to taste harsh
Threats to grapes when they first get to the winery
- Ambient yeast
- Oxidation
- Bacteria (ie acetic acid bacteria)
- Warm temp
How to minimize threat of oxidation & microbial infection during transport to winery?
- Pick at night or at cool temps
- Put grapes in smaller crates so they dont get crushed
- Spray crates w/ So2 or upon arrival
- Storing grapes in cool storage upon arrival
- Sanitizing all equipment used
Order of processes once grapes arrive at the winery:
- Chill
- Sort
- Destem (optional)
- Crush (optional)
Ways to sort grapes
- Hand harvest
- Sorting by hand on a table or vibrating belt
- Optical sorting (only for premium/super premium wines)
When would you not destem your grapes?
- Whole Cluster/Bunch Fermentation (some whites like for high quality sparkling will also be whole cluster)
- Carbonic Maceration
Whata is Must?
The mixture of grape juice, pulp, skins, and seeds. AKA substance being fermented
Types of Batch Presses
- Pneumatic Press
- Basket Press
- Horizontal Screw Press
Pros of Pneumatic Presses
- Can adjust pressure depending on desired extraction
2. Can be flushed with inert gas to prevent oxidation
Pros of Basket Press
- Most gentle press method
Cheapest Press Method
Continuous Press - quicker, less gentle than pneumatic and basket, used for high volume inexpensive wines