Sodium Hydroxide (NaOH)

Definition - What does Sodium Hydroxide (NaOH) mean?

Sodium Hydroxide (NaOH) is an inorganic compound utilized to calculate grapes' acidity levels prior to harvest in order for the winemaker to determine the fruits' maturity level, balance of sugars and various acids.

In the laboratory, samples of grapes are brought in where the juice is then tested for its Titratable Acidity (TA). Sodium Hydroxide has the ability to change in color due to a special indicator called phenolphthalein. As the titration is performed, the amount of Sodium Hydroxide added upon the color change of solution is recorded, and the level of acidity in the juice of the grapes is determined.

WineFrog explains Sodium Hydroxide (NaOH)

Sodium Hydroxide (NaOH) is a useful compound in a winery's laboratory to identify the acid content of grapes. Throughout the last month of the growing season, samples of grapes are taken from the vineyard, with an even selection from sometimes each vineyard row or separate varietal and then brought to the lab. The grapes are then mashed together to mix the grapes' juices in order to obtain a more exact read on current acidity levels.

The grape juice is then added to a beaker with a stirring rod where it sits below a burette to allow a slow and measurable drip of NaOH to the juice. A pH meter is placed in the juice while the Sodium Hydroxide is slowly dripped in. When the solution of the grape juice and NaOH changes color, the titration is stopped and the acidity can then be calculated.

The 3 natural acids found in grapes are:

  • Malic acid
  • Citric acid
  • Tartaric acid


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