Acidity Testing in Food

Acidity determination plays a critical part in ensuring that consumer products meet requirements for attributes such as appearance, texture, taste and nutritional content. It guarantees that foods and beverages are produced for consumers with consistent, well-defined properties including shelf-life.

Acidity testing is also vital in ensuring products meet regulatory requirements and do not present safety or health issues for the consumer. In short, acidity is an important attribute of many foods and drinks.

Learn how acidity affects food processing, and how accurate acidity testing helps to ensure product quality in the food and beverage industry, download our guide “An Introduction to Acidity Analysis: Selected Techniques to Monitor pH and Acids”.

Acidity measurement is the main criteria to indicate freshness and composition of raw ingredients and perishable foods. A quick pH assessment can determine, for example, whether raw oysters have been cleaned well enough to prevent food poisoning, or hint at the presence of mastitis in dairy herds.

Titration furnishes more detailed clues for certain perishable items – including milk, oil and fruit juices – that are sold as blends or may be subject to adulteration. For example, milk with elevated levels of lactic acid may be contaminated with bacteria, while tartaric or malic acid in blended juices points toward the presence of certain types of fruit. In products like fresh juice, this testing can be an important part of meeting local labeling requirements, in addition to preventing allergic reactions or other forms of illness.

As noted, the results of a food or beverage’s acid content determination can indicate how long it will last on shelves, often paired with strict temperature-control requirements. The United States Code of Federal Regulations (CFR), Title 21, Part 114 stipulates that most foods and beverages preserved via acidity must be assessed by an approved method. Potentiometric measurement via pH or titration is suitable for products with a pH between 4.0 and 4.6, with the results related to the final equilibrium pH. By contrast, any method may be used for foods with a pH below 4.0.

There are two interrelated concepts in F&B analysis that involve acidity: pH and titratable acidity. Each has its own impact on food quality. Titratable acidity measurements deal with the total acid concentration of a food (also called total acidity). pH measures acidity in terms of H+ ions present in the sample (also called active acidity).

pH indicates a food or beverage’s degree of acidity or alkalinity. A pH meter measures this acid strength in terms of the potential difference between a reference electrode (like Calomel or Ag/AgCl) and a pH electrode (glass electrode). This difference is then related to the concentration of H+ ions in the solution and corresponds to the acidity of the solution.

Foods and drinks display a broad range of pH values, which relate to the sample’s acidity or alkalinity. Some foods such as meat, dairy products, alcohol, lemon juice, carbonated water, and vinegar fall towards the acidic end of the pH spectrum, whereas common vegetables and fruits fall towards the alkaline end, as shown in the following table.

Titratable or total acidity can be determined by titrating the known amount of sample using a titrator along with a sensor or indicator. Depending on the type of titration, the titration endpoint can be determined by sensor or using a color indicator. This technique provides a more accurate acidity testing method for the total acid content of the sample. Acid-base titration, redox titration and colorimetric titration methods are used to determine acid content using titration.

Titration instrumentation and sensors
METTLER TOLEDO offers a robust range of titration instrumentation, including automated titrators, that can help improve the accuracy and speed of your acidity titrations in F&B processing. Our various titration types and instrumentation can help you perform accurate and reliable acidity content determinations in the food and beverage industry.

Based on the type of titration as well as depending on the titrator used, we offer a broad portfolio of sensors to meet your food and/or drink quality control needs. Our sensors can help you with accurate total acidity measurements for foodstuffs and liquids such as wine and fruit juices.

Ensuring accuracy and repeatability in sample preparation is critical when seeking to meet quality control requirements and guarantee consumer safety in industries such as F&B. To enhance sample preparation repeatability, accuracy, and speed, METTLER TOLEDO offers a suite of analytical instruments designed to help you increase throughput while reducing both time-to-result and per-sample processing costs.

We offer several application notes regarding acidity determination that focus on specific food and beverage products. Noted in the table below, these helpful documents discuss specific sample types to help you obtain accurate acidity analyses across the food production value chain.