Canning became popular in the 19th century, initially to provide food for military troops. This method preserved seasonal foods, making them available year-round. However, it also introduced safety concerns, especially the risk posed by Clostridium botulinum. To address these risks, the U.S. Food and Drug Administration (FDA) established guidelines (21 CFR Parts 113-114).

Understanding pH in canned foods

Canned foods are categorized as either acid foods or low-acid foods. Acid foods naturally have a pH of 4.6 or below. Low-acid foods, which include meats, seafood and certain vegetables, have a pH above 4.6 and a water activity greater than 0.85. These low-acid foods must either be acidified to maintain a pH below 4.6 or be thermally processed to ensure safety.

The importance of pH measurement

pH measurement is crucial in ensuring the safety of canned foods. According to FDA regulations (21 CFR 114.80), the pH must be monitored frequently throughout manufacturing to prevent spoilage and microbial growth. Potentiometric methods are mandatory for foods with a pH above 4.0.

Challenges in measuring pH

Standard pH sensors face difficulties when used with solid or semi-solid samples. Issues like sensor damage, clogging, and inaccurate readings are common. Preparing samples by blending them into a slurry can be time-consuming and prone to errors.

InLab Solids Pro-ISM: A specialized solution

Mettler Toledo's InLab Solids Pro-ISM sensor is specifically designed to address these challenges. This sensor features a spear-shaped tip made of toughened glass, allowing direct insertion into solid or semi-solid food samples without the need for blending. The low-temperature glass sensing membrane ensures low resistance and fast results. Additionally, the open junction design eliminates the risk of clogging, which is common in conventional ceramic junction sensors.

The InLab Solids Pro-ISM sensor also incorporates Intelligent Sensor Management (ISM®) technology, which provides accurate capture of critical measurement parameters. The sensor's solid XEROLYT®EXTRA polymer reference system interacts with the sample through diffusing ions, addressing the immiscibility of aqueous reference electrolytes with the sample.

To learn more about the procedure for measuring pH in canned food, download this application note.

Maintenance and best practices

Proper care and maintenance of the sensor are crucial for optimal performance. After measurement, the electrode should be cleaned with ethanol or acetone and rinsed with deionized water. Based on sensor performance, periodic reconditioning in 0.01 M HCl is recommended. To remove protein build-up, the sensor should be soaked in a pepsin/HCl solution for one hour every two weeks.


To contact the author of this article, email pHmatters@mt.com