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High-intensity ultrasound technology processing lettuce

High-intensity ultrasound technology is transforming food processing, offering multiple benefits that include enhanced product quality, efficiency, and food safety. By generating powerful sound waves, this technology improves processes like extraction, homogenization, dehydration, and emulsification, meeting the food industry’s demand for energy-efficient, sustainable, and non-thermal methods.

“Companies want to reduce their carbon footprint with the goal of becoming carbon neutral,” says Hao Feng, Blue Cross Blue Shield Endowed Professor of Urban Food Systems and professor of food bioprocess engineering at North Carolina Agricultural and Technical State University, in Greensboro. “Ultrasound technology—which utilizes acoustic energy to perform a wide range of food processing operations—contributes to that goal, offering a clean production environment and less waste.” 

A member of IFT’s Nonthermal Processing and Food Engineering Divisions, Feng has long spearheaded research in the field; his Ultrasound Technologies for Food and Bioprocessing, coauthored in 2011, was the first book on the topic written by food scientists. In the conversation below, he elaborates on his ongoing research to advance high-intensity ultrasound technology and its powerful potential for the future of food processing. 

Explain your accomplishments in applying high-intensity ultrasound to food processing.

My lab developed the first variable frequency non-thermal ultrasonic drying prototype to dry fruits and vegetables, as well as plant protein suspensions such as pea and hemp, nano-emulsions, egg whites, and more. What’s unique about this technology is that drying can be done at relatively low temperatures, like 30 or 40 degrees Celsius, and because of that, we call it non-thermal drying. In all the food samples we’ve studied, we’ve observed a significant reduction in drying time compared to traditional hot air drying and also significantly improved quality attributes. In many cases, like for pea and hemp protein, the quality of non-thermal ultrasound dried samples is comparable to freeze dried samples. The big benefits are: reduced processing time, reduced energy consumption, and reduced carbon emissions. Also, because temperatures remain low and processing time is short, there is less thermal damage to structures like proteins. This boost in quality retention is a big plus. 

Talk about technologies you’ve developed specifically tailored to food safety. 

My lab developed the first continuous-flow mano-thermo-sonication (MTS) liquid food processing system. MTS is a food preservation technique that combines heat, pressure, and ultrasound to pasteurize liquid foods. Our system is used to inactivate foodborne pathogens and enzymes in juices to achieve the FDA-required 5-log pathogen reduction performance standard. We’ve seen that the juice processed is of better quality, compared to the more common pasteurization treatment for liquids. Another technology pertains to fresh produce sanitation. We’ve developed the world’s first large-scale, continuous flow ultrasonic fresh produce washing machine (with a patent application). The system can ensure uniform ultrasound treatment to dislodge and inactivate foodborne pathogens attached to produce surfaces. We’ve achieved a significant enhancement in bacterial inactivation over that of a traditional chlorine wash. 

How does high-intensity ultrasound promote environmental sustainability?

Ultrasound is a green technology due to its energy efficiency, reduction of harmful chemicals, lower resource usage, faster processing times, and minimal environmental impact. Ultrasound is generated by piezoelectric crystals that convert electrical energy into mechanical energy in the form of high-frequency vibrations, making it an electrification process. If the electricity used is sourced from renewable energy, ultrasonic processing can help to achieve carbon-neutral operation.

What are the challenges to implementing it? 

The equipment manufacturing capacity for high-intensity ultrasound applications is still limited. Right now, there is no specialized ultrasound equipment manufacturer for food processing in the United States, and this is a big hurdle. Attention must be paid to the problem of ultrasound non-uniformity in equipment and process design, as well as some of the challenges posed by high energy level applications. We need more R&D and interest from the food industry, so that more manufacturers can move into this area. 

You will direct the Urban and Community Food Complex once it opens at the N.C. A&T University Farm in 2025. How will it build upon your processing expertise to benefit the food system in your area? 

This new facility will provide us with comprehensive food processing and product development capabilities, ranging from benchtop R&D, pilot testing, and quality analysis to sensory evaluation and marketing. It offers the necessary infrastructure and facilities to function effectively as a technology incubator for the local area, supporting the development of various food products and generating income to help combat food insecurity in urban communities. 

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