The crystal-like deposits sometimes observed in bottled wines (often called “wine diamonds”) are best characterized by which statement?

Introduction / Context:
Occasional glassy crystals in wine bottles alarm consumers, but they are typically harmless potassium bitartrate crystals (“wine diamonds”). Understanding their origin and prevention is useful in wine quality control and customer education.

Given Data / Assumptions:

• We address visibly crystalline precipitates, not haze or microbial films.
• Cold stabilization is a common winery practice.

Concept / Approach:
Potassium bitartrate (KHT) can precipitate when wine is chilled, forming clear, shard-like crystals. Cold stabilization holds wine at low temperatures to force precipitation in the tank rather than in the bottle. These crystals are not diatomaceous earth, tannin, or necessarily linked to high malic acid; they are a tartrate stability issue.

Step-by-Step Solution:

Verification / Alternative check:
Winery SOPs include cold stabilization or alternative tartrate stabilization methods (contact seeding, electrodialysis) specifically to prevent in-bottle crystal formation.

Why Other Options Are Wrong:

• Diatomaceous earth: a filtrant; residual DE is filtered out and is not crystalline tartrate.
• Tannin precipitates: look different; not glassy crystals.
• Excess malic acid: unrelated; tartrate crystals derive from tartaric acid salts.
• Always spoilage: false; tartrate crystals are benign.

Common Pitfalls:
Assuming any solid in the bottle equals spoilage; misunderstanding that tartrate crystals are natural and harmless.

Final Answer:
They are prevented by cold stabilization of the wine