Should grapes be frozen before making wine?
As a sommelier and brewer, I have encountered the technique of freezing grapes in winemaking, known as cryoextraction. This method aims to modify the composition of the final wines by utilizing the changes that occur in the frozen grapes. The process of freezing grapes facilitates the transfer of certain compounds from the grape skins into the musts, primarily due to the grape's unstructured tissues.
One of the main advantages of freezing grapes is the enhanced extraction of flavor compounds. When grapes are frozen, the water inside the cells expands, causing the cell walls to rupture. This rupture allows the release of various compounds, including phenolic compounds responsible for the flavors and aromas found in wine. The increased extraction of these compounds can contribute to a more intense and complex flavor profile in the resulting wine.
Furthermore, freezing grapes can also lead to an increase in sugar concentration. As water freezes, it forms ice crystals, leaving behind a more concentrated juice. This concentration of sugars can result in a higher alcohol content in the finished wine. However, it is important to note that the degree of sugar concentration will depend on the freezing technique used and the duration of freezing.
In addition to flavor and sugar concentration, freezing grapes can also affect the acidity of the resulting wine. During freezing, tartaric acid, one of the primary acids found in grapes, can precipitate out of the juice. This can result in a reduction of acidity in the final wine. Winemakers may choose to freeze grapes to achieve a specific acid balance in their wines, particularly in regions where grapes tend to have higher levels of acidity.
It is worth mentioning that the technique of freezing grapes is not commonly used in all winemaking regions or for all grape varieties. It is more prevalent in cooler climates where grapes may not fully ripen before the onset of frost. In such cases, freezing the grapes can help to concentrate flavors and sugars, compensating for the shorter growing season.
However, freezing grapes is not without its challenges. The process requires careful temperature control to avoid over-freezing or damaging the grapes. Additionally, the frozen grapes need to be thawed gently to prevent excessive oxidation or loss of flavor. The winemaker must also consider the potential loss of volume during the freezing and thawing process.
The decision to freeze grapes before making wine depends on the desired outcome and the specific characteristics of the grapes and the winemaking region. Freezing grapes can enhance flavor extraction, increase sugar concentration, and potentially impact acidity in the resulting wine. However, it is a technique that requires careful handling and consideration of potential drawbacks. Ultimately, it is up to the winemaker to determine whether freezing grapes aligns with their winemaking philosophy and desired style of wine.