Young wines are supersaturated in potassium bitartrate, which induces rather uncontrolled crystallization processes. Delayed crystallization may occur even after bottling of the young wines, which is undesirable because it gives rise to a visual defect in the wine. Colloids such as mannoproteins, metatartaric acid, and carboxymethylcellulose are available on the market and may be added to delay crystallization. It has been a matter of debate whether such hydrocolloids prevent nucleation, growth of crystals, or both. It was the objective of this investigation to study the crystallization event by a new approach using dynamic light scattering and to clarify the mode of action of these hydrocolloids. To achieve this, model solutions and standardized wines were enriched with potassium bitartrate (KHT) to trigger crystallization. In this way, it was possible to distinguish between the influence of the hydrocolloids on nucleation and on crystal growth. It was found that the hydrocolloids do not prevent KHT nucleation. Instead, these compounds delay or even arrest the outgrowth of the crystals to a macroscopic, visual size.
Keywords: DLS; KHT nucleation; carboxymethylcellulose; colloids; crystallization; mannoproteins; metatartaric acid; potassium bitartrate; potassium hydrogen tartrate; tartrate crystals; wine; yeast polysaccharides.