Individually quick freezing and Listeria: What’s happening

Recalls of individually quick frozen foods (IQF) have been widespread recently throughout the U.S. and Canada after Listeria was found in a food production facility during a random sampling by the Canadian Food Inspection Agency.

Over 24 IQF products shipped throughout the U.S. and Canada were recalled, including broccoli, cauliflower, stir fry medleys, and vegetable and hummus trays. There have not been any reported illnesses related to the products that led to the recent voluntary recall.

Even though the foods involved had undergone the IQF process, they aren’t necessarily in the clear. Listeria can survive the extreme cold of the IQF process. This means that even packaging operations with the most stringent sanitation practices need to test for Listeria at multiple points throughout the course of their processing. By doing so, they can protect their consumers, brand, and partners from a costly mishap.

The IQF method was originally realized when a biologist noticed something else that survived extreme cooling. While ice fishing in freezing cold temperatures, the biologist noticed the fish he caught froze instantly when resting on the snow — so quickly that their cells avoided being ruptured. As a result, upon being thawed, some of the fish survived.

The same concept applies to the IQF process, which freezes food products extremely fast, speeding past the 25–31°F temperature range (at which larger, cell-damaging ice crystals develop) and allowing produce to retain its water content.

Although IQF operations leverage the same quick freezing strategy, the process leading up to that stage varies greatly depending on the type of produce. For example, while the process for peas includes blanching and cooling, the process for fruit differs, as fruit does not react well to high heat.

Because of these differences, the production zones most at-risk for contamination will be different depending on the produce. However, the need for Listeria testing at various points before, during and after the IQF process remains constant across all produce types. With testing, producers can more precisely locate contaminants in order to clean their systems, save produce and protect themselves from a costly product recall and diminished brand reputation.

The U.S. Centers for Disease Control and Prevention estimates that 1,600 people develop a serious form of the infection known as listeriosis each year, and 260 die from the disease, making it the third most deadly form of food poisoning in the U.S.

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