Acidity and Acid Content Determination Guide
Acidity is an important topic within the food industry. There are personal and cultural differences in taste and considerations about storability that make a close monitoring of acidity in food products necessary.
Not only does acidity affect the flavor, it also influences the growth ability of microorganisms, such as bacteria and fungi. Accuracy of acidity measurement will help you on your way to compliance excellence and increased food safety.
The Ultimate Acidity and Acid Content Determination guide reviews different methods of acidity and acid content with the use of pH meters and titration, depending on the product and result requirements. Download the guide and learn more about:
- How acidity can influence the quality of a food product
- Different methods and applications for acidity and acid content determination
- Tips and hints to help prevent errors
The Ultimate Acidity and Acid Content Determination Guide
Proven Analytical Methods and Results
Acidity of food items is an important topic within the food industry. There are personal and cultural differences in taste and considerations about storability that make a close monitoring of acidity in food products necessary.
The following guide will review different methods of acidity and acid content determination, depending on the product and requirements.
Table of contents:
2. Solutions Overview
3. Titration Determination
• Ascorbic Acid (Vitamin C) Determination
• Citrate Content Determination
• Sulfurous Acid / Sulfur Dioxide
4. pH Measurement
6. More Information
Acidity is an important parameter in food. Not only does acidity affect the flavor of the food item in question, it also influences the growth ability of microorganisms, such as bacteria and fungi. Commonly, the higher the acidity of a food item, the less likely are the chances that it is spoilt by microorganisms. To give an example: The most dangerous and most probably best known microorganism in food is Clostridium botulinum, a bacterium that produces several toxins and has caused innumerous deaths in humans. Acidity helps to inhibit the growth of the bacterium and thus allows commercial food processors to use a hot fill process, rather than the otherwise required minimum of about 121 degree Celsius. This reduces the cost of filling significantly.
Acid foods depend on one or more food acids such as citric, malic, or acetic acid to achieve stability. The preserving properties of acids have long been known and utilized from ancient times onwards to preserve food. It is commonly referred to as pickling. Pickling is the process of preserving food by anaerobic fermentation in brine to produce lactic acid, or storing it in acidic solutions, such as vinegar. It is said to have started 4000 years ago in India, with the production of 'achar' from native cucumbers.
Acidity in food is a strongly regulated topic. To give an example: In the USA, the FDA classifies foods with a pH at or below 4.6 into 4 categories: Acid, formulated acid, acidified and exempt.
Acid foods are foods that have a natural pH of 4.6 or below. Examples are most fruits.
Formulated acid food
A formulated acid food is a majority acid food that has very small quantities of low acid foods. Example are food dressings (mayonnaise) and condiment sauces (ketchup, barbecue sauce).
“Acidified foods” are low-acid foods to which acid(s) or acid food(s) like vinegar are added. They have a water activity greater than 0.85 and have a finished equilibium pH of 4.6 or below. Examples are pickled cucumbers and pickled peppers.
An exempt food is either (a) kept refrigerated or (b) has a water activity of 0.85 or less. Carbonated beverages are excluded. An example is chocolate sauce.
Acidity of food items is commonly measured with pH meters and titrators. pH meters (and electrodes) measure the pH value. Titration delivers accurately the acid content. Acidity often also indicates whether a food item is fresh and/ or has been stored properly. A few examples:
- A pH lower than 6.8 in fresh milk is an indication for a leukocyte infection of the cattle.
- The pH of the wash water of oysters indicates whether the cleaning process is completed. Otherwise potentially fatal toxicscan be transferred to the person eating the oyster.
- Reducing the pH of pasteurized items and cold salads (often at pH 5.3) to 4.1 prolongs the shelf life.
- Small changes in the pH of spring or well water can indicate a possible fouling of the natural strata.
The following chapters of this guide will give deeper insights into applications, methods and advice for acidity and acid content determination.
2. Acidity and Acid Content Determination Solutions Overview
Acidity and Acid Content Determination
Titration – the classic quantitative chemical analysis – is the ideal method to determine acidity and acid contents in all kinds of samples. METTLER TOLEDO offers a comprehensive range of automatic titrators to match the needs of customers from all workplaces in the food and beverage segment.
The pH value is another parameter which is measured very frequently and is related to acidity. pH is not solely measured in samples in the food and beverage industries, but is a basic parameter in practically all labs. The reading of an indicator paper was often sufficient in the past. Nowadays, results need to be more precise, more accurate and traceable. Thus, pH meters and electrodes for lab bench or portable use are applied. Select the right meter and the right electrode from METTLER TOLEDO’s comprehensive range to fit your requirements.