Guide to pH Analysis for Winemakers

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Why pH Matters?

pH is one of the most important analytical tests in winemaking. pH measurements start with harvest and conclude once the wine has been bottled. The accuracy of a pH measurement will impact many winemaking operations such as fermentation, aging, fining, stabilization, and bottling. Improper calibration, storage, or cleaning of the pH electrode may cause inaccurate readings which will impact the chemistry and sensory perception of the wine.

What is the desired pH range?

A pH between 3.0 and 4.0 is optimal for most wines. Although some winemakers will craft a wine outside this range, the risks must be considered. Wines in the higher end of this range run the risk of spoilage.
What pH range should you aim for?
Must/Juice pH Finished pH
White wines
< 3.3 pH
3.0 to 3.3 pH
Red wines
< 3.4 pH
3.3 to 3.5 pH

How does pH affect the chemistry of your wine?

● Microbial stability

Prevents spoilage by inhibiting microbial growth

● Sulfur dioxide (SO2)

Increases the effectiveness of SO2 to protect wine and juice against spoilage; required for proper calculation of SO2 addition

● Malolactic fermentation

Affects performance of malolactic bacteria to convert malic acid to lactic acid.

● Protein stability

Plays a role in haze formation and its treatment.

● Sensory attributes

Influences the appearance, aroma, and taste.

What You Need for correct pH measurment?

● pH meter

Must have – 2 point calibration, temperature compensation, 0.01 pH resolution. Good to have – Calibration check, GLP, logging.

● pH electrode

Must have — PTFE junction, glass body, combination. Good to have — Built-in temperature sensor.

● Labware

100 mL sample beakers (2), lab wash bottle with deionized or distilled water (1).

● Calibration buffers

Calibration ensures the electrode is synced to the meter. Use pH 3.00 and pH 7.01 buffers for optimal results.

● Cleaning solutions

Clogged junctions are the number one reason for poor performance in pH measurement. In wine this is particularly important because wine samples (must, juice etc) leave residues on the junction of the pH electrode that will clog it.

● Calibration buffers

Calibration ensures the electrode is synced to the meter. Use pH 3.00 and pH 7.01 buffers for optimal results.

● Cleaning solutions

Clogged junctions are the number one reason for poor performance in pH measurement. In wine this is particularly important because wine samples (must, juice etc) leave residues on the junction of the pH electrode that will clog it.

● Storage solution

A dry pH electrode is the second most common reason for poor performance in pH measurement. A dry pH bulb slows the exchange of ions (pH reading), creating false readings (you record the pH value because you think it is stable, but it is still drifting), or worse prevents the electrode from working.

● Refilling solution for electrodes

● Refilling solution for    electrodes

The filling solution of a pH electrode becomes contaminated through the testing process. Emptying out the filling solution and replacing it with fresh solution will help rejuvenate the electrode making it faster, and more responsive.
How to Measure?

1. Calibration

a. Prepare the electrode

  • Remove the protective/storage cap from the electrode.
  • If the pH bulb is dehydrated, store in storage solution overnight.
  • Remove the fill hole screw cap.

b. Prepare the calibration buffers

b. Prepare the      calibration buffers

  • Fill 2 beakers with enough pH buffer solution 7.01 to cover the pH electrode junction (approximately 75 mL in a small beaker). Use one of the beakers to rinse the pH electrode and the second for the actual calibration.
  • Repeat for pH 3.00 buffer.

c. Perform a calibration

  • Rinse the pH electrode in the pH 7.01 rinse beaker and stir gently for 4 to 6 seconds.
  • Place the electrode in the pH 7.01 calibration beaker and stir gently for 4 to 6 seconds. Wait for the reading to stabilize (digits on the LCD stop changing for at least 5 seconds) and confirm the calibration.
  • Rinse the pH electrode in the pH 3.00 rinse beaker. Stir gently for 8 to 10 seconds.
  • Place the electrode in the pH 3.00 beaker and stir gently for 4 to 6 seconds. Wait for the reading pH reading to stabilize and confirm the calibration.

HANNA NOTE

  • Calibrate the electrode after extended storage, cleaning, and before use.
  • If readings are slow to stabilize (more than 30 seconds) the electrode may need to be cleaned or the electrolyte may need to be changed.

2. Measure

  • Do not start taking measurements unless the pH electrode has been properly hydrated and calibrated.

  • Fill 2 beakers with enough sample (juice, must, etc) to cover the pH electrode junction (approximately 75 mL in a smallbeaker). Use one of the beakers to rinse the pH electrode and the second for the actual measurement.
  • Place the electrode in the rinse beaker and stir gently for 4 to 6 seconds.

  • Put the pH electrode into the sample until the junction is fully immersed.

  • Wait for approximately 1 minute before recording your measurement (the pH reading is stable when the digits do not change for at least 5 seconds).

3. Clean and store

  • Once you are finished measuring your samples, rinse the pH electrode with water until all wine stains are removed.
  • Examine the pH electrode to determine if it needs to be refilled with fill solution (the level of the internal solution is less than ½ inch from the fill hole).
  • If it is clear that wine/must is present inside the pH electrode (easier to spot with red wines because you see the red stains inside), then empty, rinse, and refill the electrode with fill solution. Close the fill hole with the cap.
  • Fill a small beaker with cleaning solution for wine deposits or wine stains.
  • Immerse the pH electrode for at least 10-20 minutes. Make sure the junction is covered.
  • Fill the storage cap of the pH electrode to the half point with storage solution and replace the storage cap on the electrode. Make sure there is enough storage solution in the cap to cover the tip  of the pH electrode.
Simple solutions for measuring pH in wine with Hanna Instruments

HI2002

edge® Dedicated pH/ORP Meter with
HI10480 Wine electrode
edge’s groundbreaking design is the culmination of Hanna’s vision, design capabilities, integrated production and world class R&D. edge is a single, easy to use meter that can measure pH and ORP.
edge screen size
Advanced pH Electrode Diagnostics edge features advanced pH electrode diagnostics to ensure worry-free measurements. Diagnostics include Hanna’s exclusive CAL CheckTM feature that alerts users to potential problems during calibration. The Sensor CheckTM feature for glass and junction integrity is enabled when using optional pH electrodes with a matching pin.

HI2002

HI10480

HI98169

pH Meter for Wine
HI98169 is a rugged, waterproof, portable pH meter for wine that measures pH and temperature of must in winemaking. This meter is supplied with a specialized pH probe that features
an open junction with Clogging Prevention System ( CPS™) technology.
  • Automatic or manual temperature compensation
  • Up to 5-point calibration settings
  • Log-on-demand feature

HI99111

Portable Wine Must and
Grape Juice pH Meter
The Hanna Instruments HI99111 is a durable, waterproof, and portable pH and temperature meter designed specifically for measurement of juices including grape juice and wine must. Automatic calibration is performed at one or two points with two sets of buffers. The calibration buffers include a pH 3.00 calibration point instead of pH 4.01 in order to better bracket the expected pH value. All calibration and measurement readings are automatically compensated for temperature variations. The split-level LCD displays both pH and temperature readings, along with indicators for reading stability, battery percentage, and calibration instructions. The HI99111 uses the FC10483 glass body, amplified pH electrode that offers numerous features that improve pH testing for a variety of juices with a high solids content.
  • pH electrode with CPS Technology
  • Automatic one or two-point calibration
  • Waterproof
For more information, contact us!
Author:
Tajana Mokrović
mag.nutr.
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