Microbial persistence during ultrasonic washing of fresh produce: from survival mechanisms to control strategies

Ultrasound is increasingly applied in fresh produce washing because of its environmentally friendly and non-thermal characteristics. However, incomplete microbial inactivation can allow surviving microorganisms to persist after treatment. This review summarizes the mechanisms underlying microbial persistence at cellular and community levels. Persistence arises from acoustic field heterogeneity, uneven cavitation, complex produce surface structures, and microbial adaptive responses to ultrasonic stress. At the cellular level, survival involves membrane remodeling, stress adaptation, sublethal injury, and formation of viable but non-culturable (VBNC) cells. At the community level, cell aggregation and biofilm formation further protect microorganisms and promote recolonization. Strategies to reduce persistence include optimizing acoustic fields and combining ultrasound with chemical agents or other non-thermal technologies. Future integration of microbial physiology, ultrasonic engineering, and artificial intelligence may enable improved prediction and control of microbial persistence in complex fresh produce washing systems while balancing microbial inactivation, product quality, and processing efficiency.