Winery Considerations Flashcards
What is cryoextraction?
Freezing harvested grape and pressing to separate solids and frozen water; grape must may also be freezed
What are measures of grape sugar concentration?
Baume (relative density of fermenting must)
Brix/ Balling (hydrometer measurement used in sugar industry; popular in new World)
Oechsle (hydrometer scale used in Germany, Switzerland)
What substance is formed if ascorbic acid is added to a wine that does not have adequate levels of SO2?
Hydrogen peroxide
What does acetic acid bacteria do?
Converts alcohol into acetic acid (vinegar); acetic acid + alcohol = ethyl ethanoate (acetone)
After how long is it considered that new barrels no longer impart much flavour on the wine?
3-4 years
What is the advantage of using pectolytic enzymes in wine making?
They help extract more clear juice from the grape flesh
What are types of presses?
Vertical screw press (basket press) Horizontal screw press (Vaslin) Pneumatic press (Willmes) Tank press Continuous screw press
What can cause a wine to smell of geraniums?
Lactic acid bacteria metabolising sorbic acid in wine
What is the most likely cause of a wine having a very unpleasant smell similar to bad eggs or drains?
Using highly anaerobic wine making techniques: Reduction causes formation of hydrogen sulfide which smells of rotten eggs
Hydrogen sulfide may be removed by aerating or adding small quantities of copper sulfate
Diacetyl is a by-product of wines that have undergone MLF, how does this impact on the wine?
It adds a buttery richness to the wine
Why are nitrogen levels important in grape fermentations?
- When there is a lack of nitrogen hydrogen sulphide (H2S) can be produced
- If it is lacking it can contribute to a stuck or sluggish fermentation–kick-start by adding nitrogen-rich products (DAP or vit B)
What are by-products of fermentation?
Glycerol (glycerine), acetaldehyde, ethyl acetate, aromas esters, fusel oils
What is and how does isoamyl isotate form?
Fermentation at low temperature causes retention of isoamyl acetate (banana/ pear drop)
What is considered an average extraction rate, as a percentage of total weight, for still wine?
70%
What types of wines is destemming not appropriate for?
Sparking and red wines that undergo carbonic maceration
What are clarification methods?
Sedimentation and racking Fining Filtration Centrifugation Floatation
What are clarification methods for whites?
Cold settling (sedimentation and racking: 5-10 degrees; can use stainless steel and rack every two months to remove lees and prevent reduction)
Centrifugation
Diatomaceous earth filtration (good for aromatic varieties)
Flotation
What are the general conditions for skin contact in aromatic white wine production?
Temperature between 5 -10°C up to 24 hours
When can hydrogen sulphide develop?
Stuck fermentation: Hydrogen sulphide formation: No nitrogen > yeast breaks down amino acids > hydrogen sulfide releases > smells like rotting eggs
Unstired lees: Unstirred > hydrogen sulphide, mercaptan odours (cabbage-like)
Bottle maturation: Extended storage > reduction (hydrogen sulphide aroma—rotten eggs)
What are must enrichment techniques?
Chaptilization (add sucrose) Add RCGM Vacuum evaporation Reverse osmosis Cryoextraction
Which of the following can eliminate hydrogen sulphide in wine?
Lees stirring
Racking
Passing through a copper pipe
Add copper sulphate
What is the impact of hyperoxidation on aromatic varieties?
Effect sometimes favourable or neutral for Alsatian and German varieties, Chardonnay, Chasselas, Garganega and Trebbiano
Considered detrimental for SB
What are cap management methods?
Pumping-over (remontage) Punching down (pigeage) Rack and return (delestage) Submerged cap Rotovinification Autovinification (extended version of pumping over)
What is thermovinification?
heating grape must to 60-80 degrees Celsius for 20-30 minutes then cooling to fermentation temperature; encourages maximum colour extraction; time-saver
What is flash expansion (flash detente)?
Fermentation technique: Place pre-heated grapes (65-90 degrees Celsius) in intense vacuum > grapes cool to 30-35 degrees > cells desrupted, rapid release of anthocyanins, tannins
Why would a vineyard manager use “plastic mulching” in a newly-planted site?
To reduce the risk of water stress damaging the young vines.
To encourage microbiological activity in the soil.
Which one of the following produces a buttery smell in wine that has undergone malolactic fermentation?
Diacetyl
Pre-fermentation cold soaking, requires which of the following?
Higher levels of SO2 to prevent spontaneous fermentation taking place
What does pH influence in wine?
Colour, taste, quantities of molecular sulfur dioxide > overall stability
What are types of oak used to make barrels?
Quercus alba: American; low phenols; high aromatics (oak lactone (coconut))
Quercus petraea: less extractable tannin; high aromatic potential (lactone, volatile phenols like eugenol (clove), phenol aldehyde like vanillin)
Quercus robur: low odoriferous compounds; high extractable polyphenol content
