Could Recycled Water in Food Factories Spread Hidden Allergens?

Food factories around the world are reusing water to save money and protect the environment. But scientists are now asking an important question: could that recycled water carry hidden allergens from one food to another? Allergens are proteins found in foods like peanuts, milk, and shellfish that can cause serious reactions in some people. A new research review says this risk has almost never been studied before, and it deserves much more attention.

The food industry uses enormous amounts of water every day. Workers use water to wash fruits and vegetables, chill meat and poultry, and clean factory equipment. Some of these cleaning processes can use up to 70 percent of all the water a facility has, and they can cost a lot of money to run. Because of this, many factories now treat and reuse the same water over and over again — sometimes for more than fifty cycles — instead of dumping it after a single use.

Reusing water is good for the planet, but it comes with risks. When food is washed or soaked in water, tiny pieces of protein can dissolve into that water. If the water is not properly cleaned between uses, those proteins can end up on the next batch of food. This is called cross-contamination, and it is a well-known problem with germs. Scientists now believe it could also happen with allergens.

There are nine major food allergens that doctors consider the most dangerous. These are milk, eggs, peanuts, tree nuts, wheat, soybeans, fish, shellfish, and sesame. A survey of 50 food safety experts found that 92 percent of food companies made products containing at least one of these allergens. That means almost every food factory is handling allergenic ingredients at some point during production.

Some steps in food processing are more risky than others when it comes to allergens getting into water. For example, tanks where food is soaked or dipped, and long water channels called flumes that carry produce through a facility, keep food and water in contact for a long time. When food is cut, peeled, or shelled, even more protein gets released into the water. The more protein in the water, the higher the chance it could end up on a different food product.

However, scientists are careful to point out that having allergens in process water does not automatically mean someone will get sick. The actual health risk depends on how much allergen ends up on the finished food, how much of that food a person eats, and how sensitive that person is to the allergen. Still, researchers say the risk should be taken seriously and studied much more carefully.

Right now, there is almost no research on whether allergens actually show up in food processing water, or whether current water treatment methods remove them effectively. The scientists behind this review want to change that. They hope their work will push food companies and regulators to start testing for allergens in recycled process water, and to make sure water treatment systems are strong enough to protect everyone — especially people with serious food allergies.