What is measured to determine the acidity or alkalinity of a food system?

The measurement used to determine the acidity or alkalinity of a food system is pH. This scale, which ranges from 0 to 14, indicates how acidic or basic a solution is, with values below 7 representing acidity, a value of 7 being neutral, and values above 7 indicating alkalinity. It's crucial in food science because the pH levels can influence flavor, preservation, and microbial growth in food products. For instance, many preservation methods, such as pickling, rely on maintaining a low pH to inhibit pathogen growth.

In contrast, water activity measures the availability of water for microbial growth and does not directly indicate acidity or alkalinity. Brix is a scale used to measure the sugar content in solutions, particularly in fruit juices and syrups, while sodium concentration refers to the amount of sodium in a food, which, though it can affect flavor, doesn't provide insight into the food's acidity or alkalinity. Thus, pH is the key metric for assessing these characteristics in food systems.