The Effect of Water Activity on the Heat Resistance of Heat Sensitive and Heat Resistant Strains of Salmonellae

Baird‐Parker, A. C.; Boothroyd, Margery; Jones, Edward L.

doi:10.1111/j.1365-2672.1970.tb02228.x

Cited by 106 publications

(54 citation statements)

References 24 publications

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“…Therefore, the thermal protective effect of media with reduced a w increased with increases in the treatment temperature. Comparing our data with those obtained by other investigators is difficult, since the effect of a w on microbial inactivation depends on the solute (1,4,9,16,31). From published data obtained for solutions of sucrose and water, it could be deduced that the effect of a w on the thermal tolerance of Salmonella serovar Enteritidis was among the highest published for Salmonella serotypes.…”

supporting

confidence: 44%

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

Álvarez

Mañas

Sala

et al. 2003

Appl Environ Microbiol

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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...

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confidence: 44%

“…For Salmonella serovar Senftenberg, the effect of a w of the heating media was lower (D t ϫ 2 or D t ϫ 3) (8,9,19). It is generally believed that the thermal protective effect of reduced a w s is higher for the most heat-sensitive species (1,8,9). Our results are in accordance with this hypothesis.…”

mentioning

confidence: 99%

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

Álvarez

Mañas

Sala

et al. 2003

Appl Environ Microbiol

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“…Published data indicate that serovar Senftenberg strain 775W is significantly more heat tolerant than are most other Salmonella strains at optimal a w (rvp 0.995) but not at low a w (6,19,21). Our data confirm that serovar Senftenberg strain 775W was relatively heat sensitive over the rvp range 0.65 to 0.90.…”

Section: Pt4mentioning

confidence: 99%

“…Sucrose was generally more protective than was glucose-fructose, which in turn resulted in significantly lower thermal death rates than with NaCl at all temperatures tested. Most published reports indicate that the heat tolerance of Salmonella increases as the a w decreases (14,21,38,58), but a small number of reports indicate that heat tolerance of Salmonella may increase or decrease at low a w (6,19,25). We propose that the temperature-dependent effects of low a w on the heat tolerance of Salmonella reflect different targets for death at low temperatures than at high temperatures.…”

Section: Pt4mentioning

confidence: 99%

“…Outbreak investigations indicate that only a very few Salmonella cells may be required to cause disease when consumed in low-a w foods (22,53). In addition, it is widely believed that cells suspended at lower a w during thermal inactivation are more heat tolerant than those suspended at a higher a w (6,14,19,21,38,58). This has clear implications for food processing when heating is used to ensure the elimination of potential food pathogens including Salmonella.…”

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confidence: 99%

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Effect of Challenge Temperature and Solute Type on Heat Tolerance of Salmonella Serovars at Low Water Activity

Mattick

Jørgensen

Wang³

et al. 2001

Appl Environ Microbiol

135

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Salmonella spp. are reported to have an increased heat tolerance at low water activity (a w ; measured by relative vapor pressure [rvp]), achieved either by drying or by incorporating solutes. Much of the published data, however, cover only a narrow treatment range and have been analyzed by assuming first-order death kinetics. In this study, the death of Salmonella enterica serovar Typhimurium DT104 when exposed to 54 combinations of temperature (55 to 80°C) and a w (rvp 0.65 to 0.90, reduced using glucose-fructose) was investigated. The Weibull model (LogS ‫؍‬ ؊bt n ) was used to describe microbial inactivation, and surface response models were developed to predict death rates for serovar Typhimurium at all points within the design surface. The models were evaluated with data generated by using six different Salmonella strains in place of serovar Typhimurium DT104 strain 30, two different solutes in place of glucose-fructose to reduce a w , or six low-a w foods artificially contaminated with Salmonella in place of the sugar broths. The data demonstrate that, at temperatures of >70°C, Salmonella cells at low a w were more heat tolerant than those at a higher a w but below 65°C the reverse was true. The same patterns were generated when sucrose (rvp 0.80 compared with 0.90) or NaCl (0.75 compared with 0.90) was used to reduce a w , but the extent of the protection afforded varied with solute type. The predictions of thermal death rates in the low-a w foods were usually fail-safe, but the few exceptions highlight the importance of validating models with specific foods that may have additional factors affecting survival.

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Introduction: Historical Highlights of Water Activity Research

Chirife¹,

Fontana²

2007

Water Activity in Foods

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The Effect of Water Activity on the Heat Resistance of Heat Sensitive and Heat Resistant Strains of Salmonellae

Cited by 106 publications

References 24 publications

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

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

Effect of Challenge Temperature and Solute Type on Heat Tolerance of Salmonella Serovars at Low Water Activity

Introduction: Historical Highlights of Water Activity Research

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