Measuring ph levels and water activity

water activity microbial growth fda

Microorganisms that cause food spoilage and degrade food quality are not the same microorganisms that cause foodborne illness. Moisture In foods, the moisture content is typically measured using water activity aw. Taking pH at home or school One of the most popular school science projects is to take the pH of water from different sources.

Measuring ph levels and water activity

Maybe for a science project in school you took the pH of water samples in a chemistry class Oxygen Different microorganisms have different oxygen requirements to survive and grow. The simplest way to reduce water is with a process which drives off water, i. Above 7, foods are considered basic. Many yogurts and dairy products contain probiotics, which are bacteria that promote healthy digestion. Pollution can change a water's pH, which in turn can harm animals and plants living in the water. For instance, water coming out of an abandoned coal mine can have a pH of 2, which is very acidic and would definitely affect any fish crazy enough to try to live in it! Therefore, it is of utmost importance that food is properly processed and preserved to prevent foodborne illness, because there are no obvious signs that foods are not safe to eat. Water activity is measured on a scale of 0.

Water with a pH of five is ten times more acidic than water having a pH of six. The amount of water removed from or added to a food depends on the nature and amount of water-soluble substances water binding capacity present in the product.

factors affecting water activity

Because of the strong influence of aw on the wholesomeness and safety of many foods, regulations specifying aw levels have been established. Therefore, aw can be used to preserve foods.

The knobs on the box are used to adjust the displayed pH value to the known pH of the solution, thus calibrating the meter. When water binds to these components, it is no longer available for microorganisms to use for growth.

Water activity and shelf life

This is often employed to delay food spoilage. Pure water has an aw of 1. Low acid foods have a pH of above 4. Inside the thin glass bulb at the end of the probe there are two electrodes that measure voltage. Pickling foods by adding acid or through natural fermentation lowers the pH enough to discourage many microorganisms. It measures the effective acidity—the degree or intensity of acidity. Almost all food falls into the acidic category pH below 7. Oxygen Different microorganisms have different oxygen requirements to survive and grow. The second method involves tying up the free water by the addition of solutes, usually sugars or sodium chloride salt. Thus, you can't have a pH of vegetable oil or alcohol. These microorganisms can eventually lead to food spoilage or even foodborne illness.

Microorganisms are used in the food industry to make bread rise, ferment beer and wine, and to make pickles and sauerkraut.

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What is Water Activity & pH?