7. FAQ's and Knowledgebase / pH measurement / pH meters and electrodes

Measuring the pH of bread dough

In the food industry, pH monitoring may be required during the production or pre-production process for a number of reasons including for microbe monitoring and taste purposes. In baking and bread-making there are a number of reasons why you would wish to know the pH – having a low pH in sourdough inhibits growth of pathogenic bacteria and in bread dough pH control agents (preservatives) may be added to lower the pH and inhibit bacteria and mould growth. It is important to be able to monitor this effectively.

 

Hanna HI-99161N pH Meter

 

How do I select the correct electrode?

Selecting the correct pH electrode for any application can prove to be a bit of a minefield! There are many features of the electrodes that have benefits in differing applications and these include:

Body material – A glass body will have more chemical resistance than plastic but may not be so suitable for all food-based applications due to fragility. We would always recommend for you to take a sample away from the production line to test in case of breakages.

Membrane shape – Spherical membranes are good for general purpose applications however if you need to pierce into semi-solid samples you should choose a conical or spear shaped electrode tip. These membranes have a smaller surface area so may have slower stabilisation times.

Junction type – Terminology around junction types can differ depending on the company you are looking at. The most common junction type is a ceramic (porous) pin which is great for general lab applications. Other junction types include ring and sleeve-type junctions and open junctions which are a specialised design that is brilliant for messy, sticky samples that are liable to cause clogging such as food samples. Each junction has different electrolyte flow rates and therefore your choice may need to take into account the effects of this such as stabilisation times and contamination of your sample. A double junction design is an added feature that can be found with these described junction types and makes the electrode more resistant to damage by the sample to the internal reference wire inside the electrode.

We stock a wide range of pH electrodes suitable for many applications including food-based testing. Below are some of the electrodes that we recommend for their suitability in testing the pH of bread dough:

 

Hanna Instruments FC202D Electrode

 

FC202D pH electrode by Hanna Instruments

Features:

The FC202D electrode has a number of features that make it a good choice for measuring pH in bread dough. It has a food-grade PVDF plastic body making it easy to wipe sticky dough off. The electrode has a single open junction design to help prevent it from becoming clogged and it is filled with viscolene gel electrolyte (therefore it is not refillable).  It features a conical glass tip shape (6 x 10mm) which is ideal for penetrating into the semi-solid bread dough. The recommended operating temperature range is between 0-50°C. This electrode features an in-built temperature sensor so you do not need to worry about using a separate one with your pH meter when readings are taken for temperature compensation. This electrode would also be a good choice for use with a variety of other semi-solid food samples such as dairy (soft cheeses) and ground meats. It has a DIN connection and is designed to be used with the Hanna Instruments HI99161.

 

Jenway 924 002 Electrode

924 002 electrode by Jenway

Features: 

The Jenway 924 002 pH electrode is another electrode that has features making it suitable for use with bread dough. It is a glass-bodied electrode featuring a spear-type tip which is ideal for piercing into the dough. It is refillable, meaning if it is looked after correctly the lifetime can be longer than with gel-filled electrodes. It has an annular ring junction which increases the surface exposed to the sample to prevent clogging that would occur in a standard porous ceramic pin. The operating temperature is 0-80°C . Whilst this electrode does not feature a temperature sensor, these are available separately with your pH meter and this exclusion helps to keep the price low. This electrode also features a BNC connection. It can be used with any BNC connection pH meter, but we recommend this Jenway model 570 waterproof meter with temperature probe as a good choice for this application.

 

SI Analytics Blueline 21PH

 

Blueline 21PH by SI Analytics

Features: 

The Blueline 21PH by SI Analytics (who are well known for producing superior quality electrodes) is another great option for pH measurement in bread dough. It features a plastic shaft, with a spear tip again ideal for piercing into bread dough. It has a plastic body, so can be easily wiped clean.  This electrode has a hole junction, meaning it won’t clog easily with the bread dough. It uses Referid gel electrolyte so is non-refillable. The operating temperature range is -5 – 80°C . This electrode comes with the standard SI Analytics connector called the plug head but adapters to BNC and DIN are available. This electrode does not have a temperature sensor, but this is available in some versions. It can be used with this waterproof pH meter, which we would recommend for this application.

 

Caring for and maintaining your pH electrodes

As always with using pH electrodes, it is essential to correctly store and care for your electrode to prolong its functional lifetime. Here we detail a couple of tips and best practices to get the most from your electrode:

  • Store the electrode correctly. Electrodes need to be stored with pH electrode storage solution. If it dries out, it may be possible to revive it by submerging in electrode storage solution for at least an hour. Drying out can lead to drift and slow response times.
  • Do not wipe your electrode. This can build up an electrostatic charge in your electrode membrane.
  • Clean your electrode regularly. Using messy or protein-based samples will coat the glass electrode and can clog the junction which can result in incorrect readings and calibration. We recommend regularly cleaning your electrode to prevent this from happening and you can read more in the importance of cleaning electrodes here. We stock a range of cleaning solutions, some of which are designed specifically for food based applications.
  • Regular calibration with pH buffer ensures accuracy of your readings. Over time, electrodes readings will drift slightly so the meter needs calibrating to keep it reading correctly. It depends on how often you use the meter but we recommend daily calibration. You can read more on our guide to electrode calibration here. We have a range of pH standards for calibration, with some ranges traceable to a number of recognised standards including ISO 17025 and NIST.
  • Open or loosen the fill hole which allows fill solution to flow through the junction and into the sample. During storage, the fill hole should be covered to prevent evaporation of the fill solution.
  • Keep refillable electrodes full
  • Ensure electrodes are fully submerged during readings.

 

If you have any questions on these electrodes or around selecting the correct electrode for your application we will be happy to help. Contact us using the form below or you can email us at 01954 233120.


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