Microbial Inactivation in Foods by Ultrasound Zhao Chen * Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA * Corresponding author: Zhao Chen, Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA, Tel: 864-650-5244; E-mail: zchen5@clemson.edu Received date: March 07, 2017; Accepted date: March 09, 2017; Published date: March 13, 2017 Copyright: © 2017 Chen Z. This is an open-access article distributed under the terms of the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Alternatives to heat treatments for food sanitization are gaining significance due to the increased consumer demand for novel methods that have less deleterious effects on food quality. Ultrasound is an emerging and promising food processing technology to replace conventional methods. Ultrasound has a strong antimicrobial capacity against a spectrum of microorganisms and has been considered as a potential food sanitization approach. There is a wide scope for further research into the use of ultrasound in food processing from both an academic and industrial perspective. Keywords: Ultrasound; Microbial inactivation; Foodborne pathogen; Food spoilage microorganism; Food safety; Food quality Editorial Some novel food sanitization techniques allow better retention of lavor, texture, color, and nutrient of foods than conventional thermal treatments (i.e., pasteurization and ultra-high-temperature (UHT) processing). Among these techniques, ultrasound has attracted considerable interest as a potential food processing approach. Ultrasound refers to pressure waves with a frequency of 20 kHz or more [1]. Ultrasound improves the inactivation of microorganisms, which is attributed to a physical process called acoustic cavitation [2]. Cavitation is the formation, growth, and collapse of gas bubbles in liquid media that can generate a localized mechanical energy [3]. Cavitation can disrupt cellular structure and functional components up to the point of cell lysis through causing severe damage to cell wall [4]. Research has been performed on the inactivation efects of ultrasound on various human pathogens in foods, such as Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7, Staphylococcus aureus, and Cronobacter sakazakii [5-8]. Additionally, it has also been widely reported that ultrasound is efective against indigenous food spoilage microorganisms [9-12], such as total aerobic bacteria, yeasts and molds, and lactic acid bacteria. Most published data on the microbial inactivation of ultrasound cannot be compared directly, because authors tested diferent processing conditions. Several parameters, such as the nature of ultrasonic waves, the exposure time, the treatment temperature, the type of microorganism, the volume of food being processed, and the food composition, can inluence the microbial inactivation of ultrasound in foods [2]. Accordingly, treatment conditions should be carefully optimized to obtain maximum killing efects. It should be noted that the lethal efects of low-power ultrasonic waves on microorganisms in foods have been found to be limited, as a high ultrasonic power is normally required to achieve a high level of microbial reduction [13]. Moreover, a variety of microorganisms are relatively resistant to ultrasound [14]. In the study of Baumann et al. [15], L. monocytogenes 10403S was found to be the most ultrasound- resistant strain among all L. monocytogenes strains tested. Due to this resistance, the application of ultrasound alone may not decrease the microbial loads suiciently to satisfy the existing microbiological requirements in food industry. In response, based on the hurdle technology, ultrasound has been applied in combination with other sanitization strategies, such as various energy forms and chemical antimicrobials, to produce synergistic efects. When Ding et al. [11] investigated the combined efects of ultrasound and slightly acidic electrolyzed water on the microbial loads of cherry tomatoes and strawberries, ultrasound enhanced the bactericidal activity of slightly acidic electrolyzed water on indigenous yeasts and molds. Scouten and Beuchat [5] reported that ultrasound had a modest enhancing impact on the efectiveness of calcium hydroxide for killing S. enterica and E. coli O157:H7 on alfalfa seeds. Similarly, Huang et al. [16] also observed that ultrasound enhanced the bactericidal efect of chlorine dioxide on S. enterica and E. coli O157:H7 on apples and lettuce. Chen and Zhu [10] demonstrated that the chlorine dioxide treatment with simultaneous ultrasound enhanced the germicidal eicacy against indigenous microorganisms on plums as compared to the sequential application. One plausible explanation for this synergistic efect is that through mechanical waves with high intensity, ultrasound cannot only disrupt microbial cells on fruit surface but also dislodge these cells and force them to be completely exposed to chlorine dioxide [10]. On the other hand, ultrasound may induce the uptake of chlorine dioxide by disturbing or stressing cell membrane, thus reducing the viability of microorganisms [14]. Above indings thus indicate that ultrasound in combination with other methods has great potential to improve the microbial inactivation in foods. Conventional methods of inactivating microorganisms in foods usually involve thermal treatments [17], which oten lead to the reduced sensory quality and the loss of beneicial human nutrients. In contrast, during ultrasound treatment, cavitation is primarily responsible for the killing of microorganisms, which may not afect the overall food quality [2]. In the work of Cao et al. [9], ultrasound was found to be efective in preserving strawberry fruit during storage for 8 d at 5°C. Chen and Zhu [10] reported that ultrasound in conjunction with chlorine dioxide maintained the postharvest storage quality of plum fruit for 60 d at 4°C. Overall, data on the inluence of ultrasound on food quality is still scarce and more investigations should thus be Journal of Food: Microbiology, Safety & Hygiene Chen, J Food Microbiol Saf Hyg 2017, 2:1 Editorial OMICS International J Food Microbiol Saf Hyg, an open access journal Volume 2 • Issue 1 • 1000e102