CL4: 5 Factors That Control Bacterial Growth in Food

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As a new month begins, quickly surveying the news reveals that more than 40 recalls were issued last month among FDA-regulated products in the United States.

Dozens of instances were connected to bacterial growth in food products ranging from organic snacks to pet food to energy bars.

Reviewing the factors that lead to these situations is as relevant now as ever for those connected to food production for humans and animals. The five factors below can be attributed for both allowing and preventing much of the foodborne illness that occurs each year.

Control #1: Temperature

On both ends of the spectrum, cold and hot temperatures impact bacterial growth.

Refrigeration can slow the replication of most microorganisms, while sufficient heat provides a kill step.

Refrigeration and flash freezing are the primary methods used on the cold end, all the way from the first stages of production to extending shelf-life for consumption.

On the hot end, boiling, grilling, baking, frying, pasteurization and extrusion are all methods used to kill bacteria.

Depending on the product, temperatures below 40 degrees and above 140 degrees may be appropriate, while storage anywhere between those two extremes is considered the “bacterial danger zone.”

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Control #2: Air Composition

Limiting the amount of oxygen available to bacteria will slow bacterial growth and kill organisms.

Canning and vacuum sealing methods have been employed historically, while newer processes like modified atmosphere packaging (sometimes referred to as gas flushing), infuse packaging with gasses like carbon dioxide, nitrogen and oxygen to extend product life while limiting bacteria.

Control #3: pH

Acidity carries an important role in the preservation of foods, and the intensity of acidity in each food is expressed by its pH value. Lowering the pH of the environment is a common approach used with low-acid foods to inhibit cellular activity.

All over the globe, products are submerged in some version of vinegar to “pickle” them. Other preservatives such as acetic acid, sorbic acid and lactic acid may be added as well.

Control #4: Moisture and Water Activity

The fourth control goes hand-in-hand with temperature considerations, but carries a heavy bent toward creating the finished product.

Drying (eliminating the free water), dehydrating (eliminating all water), baking and extrusion each represent methods of controlling moisture and water activity. Microorganism growth can be stunted by reducing the moisture available.

Control #5: Supply of Nutrients

Bacteria require energy to live and grow, and food provides that energy during the production process in the form of nutrients.

Limiting nutrients slows bacteria growth and replication, and sanitary design and cleaning processes are vital to ensure no food product or equipment factor is providing an environment for bacteria.


The CL:4 Series is an ongoing resource for food quality & safety professionals. Chestnut Labs provides easily-digestible food safety info and answers in 400 words or so.

Bryce Wilks