stability decisions Flashcards
What defines wine stability?
Resistance to unwanted chemical changes; stable wines show little/no unexpected changes, unlike unstable wines.
How is stability different from taints/spoilage?
Stability refers to chemical resistance; taints are exogenous contaminants (e.g., smoke, plastics), spoilage is microbial.
What are common crystalline deposits in wine?
Potassium hydrogen tartrate (boat-shaped), calcium tartrate (prism), calcium oxalate (needle), ellagic acid (needle).
How is potassium bitartrate (KHT) instability treated?
Cold stabilization (low temps), seeding with cream of tartar, metatartaric acid (short-term), or electrodialysis.
What are preventative treatments for KHT?
Mannoproteins (MP40), carboxymethyl cellulose (CMC), gum arabic—all inhibit nucleation persistently.
What causes copper instability?
Copper + sulfur + protein under reductive conditions forms red-brown precipitates; treated with blue fining (ferrocyanide).
How is iron instability identified/managed?
Iron + phosphate/protein or polyphenols forms white/blue-black precipitates (>6 mg/L); use phytate, citric acid, or chitosan.
What are amorphous deposits?
Irregular, grainy particles: proteins, metal complexes, polysaccharides, tannins—hard to resolve visually.
What consumer expectations exist for wine stability?
Whites: clear, no haze/deposits. Reds: haze/deposits tolerated in aged wines; varies by market.
What analytical tests detect KHT instability?
Cold tests (freeze-thaw), conductivity tests (Stabilab), or theoretical calculations (Mextar software).
Why avoid calcium in wine?
Forms calcium tartrate (less soluble than KHT); cold treatment is ineffective; use Enocrystal Ca or limit calcium additions.
What is electrodialysis?
Removes potassium/calcium via ion-selective membranes; alternative to cold stabilization for tartrate stability.
How does oxidative/phenolic instability manifest?
Haze/color changes after air exposure; managed with sulfites, fining, or avoiding laccase (enzyme).
What are non-instability foreign materials?
Cork dust, bentonite, DE—externally introduced but not chemical instabilities.
What organoleptic impacts do instabilities have?
Appearance (haze), color shifts, aroma/flavor changes, mouthfeel alterations—critical for consumer acceptance.
