Impact of power ultrasound on the quality of leafy green produce through a multifrequency, multimode, modulated system

Authors: Zhou, Bin; De Frias, Jose; Luo, Yaguang; Fonseca, Jorge; FENG, HAO - North Carolina Agricultural And Technical State University

Submitted to: Ultrasonics Sonochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2024
Publication Date: 2/1/2025
Citation: Zhou, B., De Frias, J.A., Luo, Y., Fonseca, J.M., Feng, H. 2025. Impact of power ultrasound on the quality of leafy green produce through a multifrequency, multimode, modulated system. Ultrasonics Sonochemistry. 113:107221. https://doi.org/10.1016/j.ultsonch.2024.107221.
DOI: https://doi.org/10.1016/j.ultsonch.2024.107221

Interpretive Summary: The fresh-cut produce industry continues to face serious challenges around food safety, as recent news on foodborne illnesses shows. Researchers are actively working on minimizing these risks, and the use of ultrasound to treat produce is a promising solution. However, as effective as ultrasound is in killing bacteria, its effect on produce quality has not been thoroughly explored. USDA-ARS scientists developed a novel and milder ultrasound system to treat lettuce and spinach and found that product quality was not affected by the treatment. A panel of trained tasters did not notice any differences in taste, texture, or appearance in any of the leafy greens studied. These findings can help the produce industry embrace ultrasound technology as a safe and effective way to improve produce safety without compromising quality.

Technical Abstract: Ultrasound technology has been increasingly explored as an eco-friendly method to improve the microbial safety of leafy greens. However, its effect on produce quality is critical, and considerable knowledge gaps remain in this area. The present study examined the responses of plant tissues (e.g., leafy greens) to ultrasound treatment as shown by tissue damage and sensory quality acceptance, using a novel multifrequency, multimode, modulated (MMM) system to address the issue of nonuniform ultrasound field distribution. Iceberg lettuce, romaine lettuce, spinach, loose leaf lettuce and Lollo Rosso were subjected to different ultrasonication durations (1 to 16 min) in a MMM tubular treatment unit at 34 kHz and subsequently stored at 1°C for three weeks. Sensory evaluations by a trained panel and electro-conductivity rate measurements were conducted to assess produce quality over time. Ultrasound treatment at an acoustic power density below 80 W/L had no significant effect (P>0.05) on the overall sensory quality of leafy greens during 14 days of storage. Although the electro-conductivity rate, an indicator of tissue damage, increased in ultrasound-treated samples compared to the control, it did not result in perceptible changes in sensory attributes. In summary, ultrasound treatments may enhance leafy green safety without compromising produce quality.