Vinegar is an aqueous solution primarily composed of acetic acid, which provides its characteristic sour taste. Standard household vinegar, typically white distilled vinegar, contains about 5% acetic acid by volume, with the rest being mostly water. Vinegar does not freeze at the temperature pure water does, remaining liquid well below 32°F (0°C).
Why Vinegar Resists Freezing
The reason vinegar resists freezing at the common freezing point of water is due to freezing point depression. Pure water molecules form a highly organized, crystalline lattice structure when they solidify into ice at 32°F (0°C).
The acetic acid acts as a solute dissolved in the water solvent. These dissolved acetic acid molecules interfere with the ability of water molecules to align into that crystalline ice structure. This disruption requires a lower temperature to overcome the interference and force the water to freeze.
The magnitude of the depression depends directly on the concentration of the dissolved particles. Since the acetic acid is evenly dispersed, it lowers the temperature threshold for the liquid to transition into a solid state. This is the same principle used when road salt melts ice or antifreeze protects a car engine.
Determining the True Freezing Temperature
For standard distilled white vinegar (approximately 5% acetic acid), the freezing point is around 28°F (-2°C). This is the temperature where the solution begins to solidify.
Calculations for a 5% acetic acid solution often yield a freezing point between -1.5°C and -2.0°C. Vinegars with higher concentrations, such as cleaning vinegars containing 10% or more acetic acid, will have an even lower freezing point because a greater concentration means more solute particles are present.
Practical Differences Between Vinegar Types
The freezing temperature can vary slightly across different types of commercial vinegars due to their unique compositions. Vinegars like apple cider vinegar, balsamic vinegar, or wine vinegar contain trace amounts of other organic compounds, including residual sugars, tannins, and various solids.
These additional dissolved components act as supplementary solutes, slightly altering the overall concentration and affecting the freezing behavior. While acetic acid remains the primary factor, the presence of these solids can cause minor variations in the precise freezing point. Unpasteurized vinegars, such as those containing the “mother,” may also show a different consistency upon freezing due to bacterial cellulose.
What Happens If Vinegar Freezes
When vinegar is exposed to temperatures below its freezing point, consequences involve both the container and the liquid. As the water component freezes, it expands, which can cause glass bottles to crack or shatter.
Inside the bottle, freezing can lead to a separation of components called fractional freezing. The water freezes first, leaving behind a liquid with a higher concentration of acetic acid and other dissolved solids. The resulting ice is mostly frozen water, while the remaining liquid becomes a stronger, more acidic solution.
Freezing does not typically make the vinegar unsafe, but it can affect its appearance, texture, and flavor profile. After thawing, the product may appear cloudy or contain sediment, requiring a thorough shaking to reintegrate the separated components before use.