Superheated “Dry” Steam: A Potential Sanitizer for Produce

By Food Safety Tech Staff
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March 26, 2023


• Categories: Food Labs, Food Manufacturing

Superheated Steam (SHS) may offer dry facilities a new, effective option to destroy pathogens on produce harvesting, processing, and packing tools. SHS differs from the visible, wet steam vapor emitted by a tea kettle in that it is invisible and acts like a hot gas at super-high temperatures. Applied to surfaces, SHS has been shown to kill pathogens without leaving moisture or condensation. However, little is known about its performance on a pilot scale.

A new research project from Abby Snyder, Ph.D., of Cornell University hopes to fill this void. As part of her research, titled “Practical application of superheated steam to harvesting, processing, and produce packing tools and equipment,” Dr. Snyder is evaluating how well SHS works and how current tools need to be improved to better support the produce industry.

She also plans to address other considerations, including cost, range of applications, wear and tear on equipment, changes to ambient relative humidity and worker safety.

“It’s a really tough problem to solve,” Dr. Snyder said. “We wanted to bring some practical assessments to our academic research to better understand whether these tools would be useful to the industry.”

Joining her as co-principal investigator is V.M. Balasubramaniam, Ph.D., with Ohio State University, who brings expertise in food and agricultural engineering. “He’s an important collaborator because the project is at the intersection of produce safety and process engineering,” said Dr. Snyder, whose background is microbial food safety. “This is an interdisciplinary approach to developing novel sanitation technology.”

The researchers are using portable pilot-scale roll-along and backpack units fabricated by a collaborating manufacturer. As part of the project, they reviewed Occupational Safety and Health Administration guidelines and developed worker safety and operator compliance training.

Initial trials looked at thermal distribution across stainless steel coupons—or discs—at ambient temperatures using three different coupon thicknesses and three different nozzle distances. Temperatures at the contact point ranged from 170 to 320 degrees C (338 to 608 degrees F), depending on nozzle distance. The researchers plan to conduct similar tests with concrete coupons as well as ones made of materials used in picking bags.

Although SHS doesn’t use large amounts of water, it is unknown whether prolonged use of the technology could change ambient relative humidity in enclosed spaces, depending on size and ventilation. As part of the project, Dr. Snyder said they will look at whether those relative humidity changes could potentially lead to condensation with extended SHS use. They also plan to characterize how rapidly temperature dissipates across surfaces.

One of the project’s objectives is to better understand how much the industry would be willing to pay for SHS technology. To that end, Dr. Snyder is conducting an online survey that proposes different scenarios.

Because SHS doesn’t use large amounts of water, the technology could offer the produce industry potential water savings in addition to more sanitation options.