This document gives a brief summary of the procedures and equipment requirements for some commonly used techniques for determination of pH of grapes and wines. Although the pH can be determined colourimetrically using organic dyes (suitable only for light coloured musts), the most frequently used technique is the potentiometric method (Amerine and Ough 1980).
Potentiometric (electrode)
Description: The pH of grape juice or wine is determined using a pH meter and electrode. This measures the amount of hydrogen ions in the wine dissociated from the acids that are present, in effect, a measure of the active acidity. Wine samples are degassed prior to measurement to remove dissolved carbon dioxide. The measurement is subject to temperature effects, arising from both sample and instrument, and must be corrected. Most meters and electrodes have automatic temperature compensation. Otherwise, it is important to ensure that the sample being measured is at the same temperature as the calibration solutions were when calibrating.
Equipment: pH meter, pH electrode, flasks and vacuum for degassing (or nitrogen gas for sparging)
Reagents: Buffer solutions for calibration
Calibration: Use standard buffer solutions, recommended daily or as per manufacturers instructions
Services: Electricity, wash up area
Space required: Small bench area
References and further reading
- Amerine, M.A.; Ough, C.S. (1980) Methods for analysis of musts and wines. New York Wiley-Interscience.
- Iland, P.; Ewart, A.; Sitters, J.; Markides, A.; Bruer, N. (2000) Techniques for chemical analysis and quality monitoring during winemaking. Campbelltown, SA Patrick Iland Wine Promotions.