Inactivation of Salmonella enterica Serovar Enteritidis by Ultrasonic Waves under Pressure at Different Water Activities

Abstract

The inactivation of Salmonella enterica serovar Enteritidis by ultrasonic waves (20 kHz; 117-m wavelength) under pressure (175 kPa) at nonlethal temperatures (manosonication [MS]) and lethal temperatures (manothermosonication [MTS]) in media of different water activities has been investigated. Heat decimal reduction time values increased 30 times when the water activity was decreased from nearly 1 to 0.96, but the MS resistance was increased only twofold. The inactivation of Salmonella serovar Enteritidis by ultrasound under pressure at low water activities was a phenomenon of the "all-or-nothing" type. A synergistic lethal effect was observed between heat and ultrasound in media with reduced water activity; the lower the water activity, the greater the synergistic effect. This work could be useful for improving sanitation and preservation treatments of foods, especially those which are sensitive to temperature and those in which components protect microorganisms to heat. It also contributes to our knowledge of microbial inactivation mechanisms by MS and MTS treatments.During the last 3 decades, the number of food poisoning outbreaks in which different Salmonella enterica serotypes were involved has increased in industrialized countries (34,35). In the late 1980s, the frequency of isolation of Salmonella enterica serotype Enteritidis from eggs and egg products has increased steadily (25, 34). The influence of different environmental factors on the survival of other Salmonella serotypes has been investigated repeatedly (12,13,15,37), but little is known about their effect on Salmonella serovar Enteritidis.It is well-known that the heat resistance of microorganisms is influenced by many environmental factors. The water activity (a w ) of the heating medium is one of the most important factors (5,7,10,16,36). The thermal protective effect of media with reduced a w is very high (100-fold) (14,33). The use of high-intensity heat treatments to obtain the required microbial inactivation would impair food quality. Therefore, perhaps the new nonthermal methods of bacterial inactivation would be good alternative methods for the preservation and sanitation of products with reduced a w .Microbial inactivation by high-power ultrasound under pressure at nonlethal temperatures (manosonication [MS]) and lethal temperatures (manothermosonication [MTS]) was first reported by Sala et al. in 1995 (29). Recently, Raso et al. (27) reported the influence of temperature, pressure, and amplitude of ultrasonic waves on the lethal effect of ultrasound. (20), it could be deduced that the eventual advantages of MS or MTS for sanitation and/or food preservation purposes will be higher in temperature-sensitive foods (e.g., when raw materials are contaminated with very heat-resistant bacterial species or when food components protect microorganisms against heat).The purpose of this work was to investigate the inactivation of Salmonella serovar Enteritidis by ultrasonic waves under pressure at different temperatures in media of different wate...

Inactivation of Salmonella enterica by UV-C Light Alone and in Combination with Mild Temperatures

“…For Salmonella, pH and water activity of the treatment medium are the most influential factors (1,29). Our results demonstrated that acidification from pH 7.0 to 3.0 did not influence the UV resistance of Salmonella Typhimurium STCC 878 (Table 2).…”

Synergistic combination of heat and ultrasonic waves under pressure for Cronobacter sakazakii inactivation in apple juice

“…All the survival curves to MS/MTS obtained were linear, as already described, for this species when exposed to MS (Arroyo, Cebrián, Pagán, & Condón, 2011b), to MTS in buffer and milk (Arroyo et al, 2011a), and for the survival curves to MTS of other species (Álvarez et al, 2003;López-Malo, Guerrero, & Alzamora, 1999;Pagán, Mañas, Raso et al, 1999). This linear shape in MTS survival curves was also found when C. sakazakii was treated at temperatures at which survival curves to heat showed shoulders.…”

“…Among them, probably the most promising ones are the combination of ultrasound with pressure (referred to as manosonication, MS), with temperature (thermosonication) or with both simultaneously (manothermosonication, MTS) (Chemat, Huma, & Khan, 2011;Condón, Raso, & Pagán, 2005;Sala, Burgos, Condón, López, & Raso, 1995). The combination of ultrasound and heat to achieve a high degree of bacterial inactivation was first reported by Ordóñez, Aguilera, García, and Sanz (1987) and since then, it has been studied by several authors (Adekunte et al, 2010;Álvarez, Mañas, Sala, & Condón, 2003;Baumann, Martin, & Feng, 2005;Ciccolini, Taillandier, Wilhem, Delmas, & Strehaiano, 1997;D'Amico, Silk, Wu, & Guo, 2006;Guerrero, López-Malo, & Alzamora, 2001;Lee, Zhou, Liang, Feng, & Martin, 2009;Pagán, Mañas, Palop, & Sala, 1999;Pagán, Mañas, Raso, & Condón, 1999;Raso, Pagán, Condón, & Sala, 1998;Raso, Palop, Pagán, & Condón, 1998;Zenker, Heinz, & Knorr, 2003). In these works, researchers demonstrated that when ultrasound was employed, both at lethal and sublethal temperatures, an increase in the inactivation rate occurred; and some of them reported an effect much greater than the additive effect of the two treatments considered independently.…”

Application of slightly acidic electrolyzed water and ultrasound for microbial decontamination of kashk

“…Microbial inactivation by ultrasound is mainly attributed to cavitation, a phenomenon that disrupts cellular structures and functions (13). Ultrasound alone may not effectively inactivate bacteria on food (14); however, combined with other treatments, ultrasound may result in higher bacterial lethality (15,16). It has also been reported that ultrasound is more efficient in a saline solution or in water (14).…”