Stability Flashcards
What is the definition of stability in the context of wine?
Resistance to unwanted chemical change in wine
Stability is distinct from maturation, taints, and spoilage.
What characterizes unstable wines?
Wines that may undergo noticeable unwanted chemical change in the future
What is wine style defined as?
A sub-set of wine requirements which align with consumer expectation
Define quality in relation to wine.
The ability to meet wine style requirements
What are taints in wine?
Trace of something bad, offensive, or harmful introduced from additives, processes, packaging
Name examples of taints in wine.
- Vine protection products
- Smoke from bushfire
- Hydraulic oil or lubricants
- Chemicals from plastics and wood products
What is microbiological stability?
Minimising microbiological spoilage to prevent chemical changes
Describe crystalline instability in wine.
Large, regular, geometrical shaped crystals, easily visible
List examples of crystalline instability.
- Potassium hydrogen tartrate
- Calcium tartrate
- Phenolic compounds
What is amorphous instability?
Irregular, different sizes, grainy materials in wine
Provide examples of amorphous instability.
- Protein
- Metal/protein
- Pigments
- Polysaccharides
- Polyphenolics
What are common consumer expectations for white wine appearance?
Clear, light colour, no deposits/haze
What are common consumer expectations for red wine appearance?
Dark colour, haze and deposits acceptable in older wine
What is Potassium Hydrogen Tartrate (KHT) classified as?
A ‘Cold’ instability influenced by temperature and alcohol
List treatments for Potassium Hydrogen Tartrate.
- Encouragement (low temperature storage, seeding)
- Preventative (additions like metatartaric acid, mannoproteins)
What is the analysis method for KHT?
Cold tests, theoretical calculations, conductivity tests
What is the primary cause of copper instability?
Reaction of copper, sulphur, and protein under reductive conditions in white wine
List strategies to manage copper instability.
- Minimisation of copper contact
- Blue fining
- Protein removal
- Gum arabic
- Chitosan
What is iron instability caused by?
Reaction of iron with phosphate or polyphenol under oxidative conditions
List treatments for iron instability.
- Minimisation of iron contact
- Blue fining
- Calcium phytate
- Citric and ascorbic acid treatments
What are common manifestations of oxidative/phenolic instability?
Haze, deposit, colour changes after air exposure
What framework is suggested for evaluating stability decisions?
- Understanding consumer expectations
- Defining stability
- Identifying sources of instability
- Knowing treatments
- Using analytical methods
What shape is Potassium Hydrogen Tartrate (KHT) typically?
Boat or lens shaped
What shape is Calcium Tartrate (CaT) typically?
Rhomboid or prism shaped
