Agricultural Research Service (ARS) scientists are studying new sanitizing methods to enhance the safety of leafy greens — technology that may result in safer salads. That's good news for health-conscious consumers. Today, sales of fresh cut lettuce and leafy greens have reached $3 billion annually, according to industry experts, and the demand is increasing.

Food technologist Yaguang Luo, with the ARS Produce Quality and Safety Laboratory (PQSL) in Beltsville, Md., first focused on reformulating a new sanitizer that works better than chlorine as a wash-solution ingredient. Chlorine solutions have been used by the food industry to help control microbes on fresh-cut greens, such as lettuce, but chlorine doesn't eliminate all the organisms that can be present.

Luo has been collaborating with colleagues at the University of Illinois to test combining the use of several sanitizers, including the new formulation, with ultrasound as a means to enhance the efficiency of sanitization prior to bagging. They conducted a study to determine the effects of selected sanitizer ingredients, with or without ultrasound, on the reduction of Escherichia coli populations on spinach.

The highest E. coli reduction was 4.5 logs — meaning the bacteria decreased from about 300,000 colony-forming units to less than 10. This reduction was achieved through combining the newly formulated wash solution treatment with ultrasound treatment.

The combination of a new sanitizer with ultrasound can potentially be used to enhance the microbial safety of leafy green produce before the bagging process, according to Luo.

ARS is a scientific agency of the U.S. Department of Agriculture.