The perfect salad dressing

We can all tell when the pH balance of a salad dressing is right, simply by tasting it. However the reason food manufacturers require reliable, accurate pH measurement is to enable storage of freshly made dressings in 'low risk' areas (microbiologically) of the factory. By keeping pH levels sufficiently acidic, 'bugs' cannot thrive and microbiological integrity can be kept intact.

Fats, suspended solids, occasional use and a sample which is an emulsion all present different challenges to a pH electrode. It is easy enough to get readings on a pH meter but careful electrode choice is essential if precision and repeatability are to be obtained.

As with all food manufacture there is a need to use a minimum of glass, so plastic bodied electrodes are usually chosen. However, it is not as easy as that - conventional electrodes will block almost immediately and 'liquid sleeve' junction electrodes are often not robust enough for the manufacturing environment. In addition to physical problems a working knowledge of the chemistry between the sample and electrode reference electrolyte are also required.

To solve a recent application problem Thermo Electron provided one of their new K-series electrodes on trial. These unique pH electrodes employ a patented cross-linked polymer as the reference electrolyte. This is a sufficiently firm gel that no physical junction (e.g. a ceramic frit) is required. A drilled hole in the plastic body allows the reference material to be in direct contact with the sample over a much larger surface area. The polymer itself is exceptionally stable and contains no silver ions - a frequent source of problems when they react with samples.

For measuring salad dressings and sauces the K-series electrode is a great improvement, stable readings are obtained quicker and cleaning is easy. An added bonus is that repeatable calibrations and minimal drift means that non-scientifically trained staff can be allowed to use it with confidence. As always an easy-to-follow cleaning and storage regime is necessary for best results and Thermo Electron supply sound practical advice with every electrode. Graduate chemists are always available for telephone support.

With the fashion for healthy eating, salads and salad dressings are often seen in the boardrooms of blue chip companies. The high demands that they place on quality assurance means that attention to detail is important. Something as routine as pH can easily be taken for granted. It cannot be stressed enough that it is a simple matter to obtain readings on a pH meter but to get accuracy and repeatability requires both careful choice of pH electrode and good laboratory practice.

Ease of use, maintenance and reliability are just as important as performance and accuracy. The system for pH measurement has been greatly improved by the K-series electrodes and the regime adopted. Excellent speed of response gives confidence in the measurement and this allows non-technical staff to achieve a high level of precision time after time.

For more information contact Sales
Thermo Electron
Station Road
Auchtermuchty, Fife, KY14 7DP.
Tel: 01337 828871
Fax 01337 828972,
e-mail sales.water.uk@thermo.com