The authentic taste and flavor of seafood greatly depend on its freshness. Considering it is a highly perishable commodity, rich in nutrients such as proteins, Omega-3 fatty acids and minerals, it becomes quite important to ensure its quality, safety and palatability. One key parameter in assessing seafood freshness is the measurement of pH, which plays a vital role in the canning and seafood processing industries.

This article explores the importance of pH measurement in seafood, how it is conducted, and tips for accurate and reliable results.

Hooked on pH: The perfect catch for quality seafood. Source: Mettler Toledo

Why pH matters in seafood

The pH measurement of seafood products helps to assign the proper storage conditions. The average pH value for fresh seafood is 6.2, though it may vary according to the type of fish. Scientific studies found a direct correlation between the pH and freshness of seafood. For example, the pH of frozen seafood tends to rise after it crosses its expiration date, indicating the onset of spoilage. It has been observed that pH can increase to 6.6 within seven days due to the production of alkaline bacterial metabolites.

Moreover, the increase in these metabolites can be assessed by estimating the total volatile nitrogenous bases in seafood samples, serving as a routine chemical analysis to evaluate spoilage levels. This information is particularly crucial for the canning industry, which depends on accurate pH data for fresh seafood to ensure effective canning processes. Continuous monitoring of pH throughout processing also helps maintain batch consistency, ensuring that seafood products meet necessary quality standards.

Challenges of measuring pH in seafood

Seafood’s solid sample nature requires sample preparation before proceeding with pH measurement when a classic sensor is used. This preparation is tedious and involves mincing the seafood meat and blending it into a paste. Such sample preparation procedures leave a high probability of errors. Moreover, the physi­cal cutting and grinding can lead to altered pH value. Unstable pH values due to sensor fouling is another common problem faced for such samples.

How pH is measured in seafood

Measuring pH in seafood requires several key steps. First, it’s important to choose the appropriate meter and sensor for the task. Next, prepare the sample properly before calibrating the pH meter to ensure accurate readings. Once calibrated, proceed to measure the pH. After completing the measurements, maintain the instruments by performing regular cleaning and ensuring they are stored correctly.

Selecting the right sensor

Traditionally, measuring the pH of seafood involves grinding the sample into a paste, which can be time-consuming and may lead to inaccurate results due to dilution effects. Conventional pH sensors with ceramic junctions are prone to clogging and require frequent cleaning, further complicating the process. While selecting the sensor for pH measurement in seafood, one must consider the recent technological advancement. An ideal sensor for this purpose could be the one with an open junction, a solid electrolyte and a spear-shaped tip that allows direct insertion into seafood samples without the need for grinding.

Some of the key features to consider are:

Low temperature glass: This durable pH membrane is resistant to breakage and delivers rapid results, even in cold environments, making it perfect for seafood analysis.

Advanced polymer reference system: This low-maintenance, clog-free reference system is specifically designed to prevent protein fouling, ensuring consistent performance and reliability.

Intelligent sensor management: This feature keeps track of calibration history, monitors temperature exposure and guarantees data security, providing users with peace of mind regarding their measurements.

To learn more about how to measure pH in seafood with InLab Solids Pro-ISM download the Mettler Toledo application note. The application note provides practical guidance on selecting the right pH meter, sensor, calibration procedures and data analysis technique, along with expert tips for optimal performance.

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