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Using Hot Water as a Solvent for Checking Food Safety

By Marty Clark
October 25, 2001

A cleaner, safer way of analyzing food by using nontoxic solvents and a new technique called subcritical water extraction has been developed by Agricultural Research Service scientists in Peoria, Ill.

Scientists Jerry King and Meredith Curren at the ARS National Center for Agricultural Utilization Research are testing subcritical water extraction to remove potential contaminants from meat samples.

Specifically, the scientists are testing the procedure to remove atrazine from meat samples. Atrazine is a widely used herbicide for controlling weeds in Midwest corn and soybean fields. Federal regulations now allow 20 parts per billion of atrazine in food, but that may change after a review by the U.S. Environmental Protection Agency, which is reviewing atrazine as a food and environmental contaminant.

In subcritical water extraction, the scientists heat highly purified water under pressure to 212 degrees F. Then the hot water is forced through a meat sample that has been mixed with an adsorbent to extract the pesticide residue.

Traditional methods employ toxic organic solvents that are costly and pose safety risks to laboratory workers and the environment. These solvents also must be disposed of safely, adding further to the cost. Filtered, purified water systems are inexpensive and don't require disposal systems. Federal agencies such as the U.S. Department of Agriculture's Food Safety and Inspection Service need safer analytical methods to check pesticide levels in foods.

In addition to addressing laboratory worker safety issues, this method is faster than other analytical techniques. Beef kidney samples are being used by King and Curren to streamline the technique by performing extraction and sample cleanup concurrently.

The hot water extraction method can also be used to analyze samples for other pesticides and antibiotics and their metabolic breakdown products. Use of this method by food-testing laboratories will ensure that Americans will continue to enjoy a food supply that ranks among the safest in the world.

A more detailed story on the research is in the October issue of the ARS magazine Agricultural Research, online at:

The Agricultural Research Service is USDA's chief scientific agency.