scholarly journals The old and the large may suffer disproportionately during episodes of high temperature: evidence from a keystone zooplankton species

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Tim Burton ◽  
Sigurd Einum
Keyword(s):  
Body Size ◽  
High Temperature ◽  
Temperature Tolerance ◽  
The Body ◽  
Acute Tolerance ◽  
Zooplankton Species ◽  
Time Curve ◽  
Death Time ◽  
Thermal Death ◽  
Thermal Death Time

Abstract Widespread declines in the body size of aquatic ectotherms have been attributed to the poorer ability of older, larger individuals to tolerate high temperature. Here, using the thermal death time curve framework, we investigate the relationship between temperature tolerance and size/age by measuring the change in heat tolerance of the keystone zooplankton species Daphnia magna across a range of temperature intensities (and hence exposures of varying duration) among individuals that differed up to 3-fold in size and thus varied in age also. Across the gradient of exposure temperatures, younger, smaller individuals were more tolerant than older, larger individuals. This suggests that the young and the small may be better equipped to withstand temperature challenges that are both intense/brief and more moderate/prolonged. Our study generalizes results obtained from more acute tolerance assays, providing physiological evidence consistent with the observed reductions in ectotherm body size as a response to warming in aquatic systems.

BACTERIOLOGICAL ASPECTS OF THE EVALUATION OF ADEQUACY OF PASTEURIZATION

1951 ◽  
Vol 14 (6) ◽  
pp. 170-172 ◽  
Author(s):  
Franklin W. Barber
Keyword(s):  
High Temperature ◽  
Dairy Products ◽  
Test Organism ◽  
Additional Information ◽  
Heat Resistant ◽  
Death Time ◽  
High Temperature Short Time ◽  
Thermal Death ◽  
Thermal Death Time ◽  
Short Time

Increased interest in high-temperature, short-time pasteurization of various dairy products has emphasized the need for methods to determine the adequacy of pasteurization. One such method is described, but there is need for additional information. The thermal death time curves of various pathogens should be determined in different dairy products. A suitable heat resistant test organism such as Micrococcus MS-102 should be selected, approved by health officials and made available to others for controlled studies. Data should be accumulated so that curves could be prepared to show any combination of time and temperature which would result in adequate pasteurization.

scholarly journals A unifying model to estimate thermal tolerance limits in ectotherms across static, dynamic and fluctuating exposures to thermal stress

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lisa Bjerregaard Jørgensen ◽  
Hans Malte ◽  
Michael Ørsted ◽  
Nikolaj Andreasen Klahn ◽  
Johannes Overgaard
Keyword(s):  
Thermal Stress ◽  
Thermal Tolerance ◽  
Accumulation Rate ◽  
Temperature Tolerance ◽  
Separate Experiment ◽  
Time Curve ◽  
Death Time ◽  
Dynamic Experiments ◽  
Different Temperatures ◽  
Thermal Death Time

AbstractTemperature tolerance is critical for defining the fundamental niche of ectotherms and researchers classically use either static (exposure to a constant temperature) or dynamic (ramping temperature) assays to assess tolerance. The use of different methods complicates comparison between studies and here we present a mathematical model (and R-scripts) to reconcile thermal tolerance measures obtained from static and dynamic assays. Our model uses input data from several static or dynamic experiments and is based on the well-supported assumption that thermal injury accumulation rate increases exponentially with temperature (known as a thermal death time curve). The model also assumes thermal stress at different temperatures to be additive and using experiments with Drosophila melanogaster, we validate these central assumptions by demonstrating that heat injury attained at different heat stress intensities and durations is additive. In a separate experiment we demonstrate that our model can accurately describe injury accumulation during fluctuating temperature stress and further we validate the model by successfully converting literature data of ectotherm heat tolerance (both static and dynamic assays) to a single, comparable metric (the temperature tolerated for 1 h). The model presented here has many promising applications for the analysis of ectotherm thermal tolerance and we also discuss potential pitfalls that should be considered and avoided using this model.

721. An analysis of the performance of an ultra-high-temperature milk sterilizing plant: II. Calculation of the bactericidal effectiveness

1958 ◽  
Vol 25 (2) ◽  
pp. 324-337 ◽  
Author(s):  
H. Burton
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Treatment Plant ◽  
Flow Time ◽  
Death Time ◽  
Thermal Death ◽  
Continuous Heat Treatment ◽  
Micro Organisms ◽  
Thermal Death Time ◽  
Continuous Heat

The purpose of this paper is to show how the performance of a continuous heat-treatment plant may be predicted from the temperature distribution and the flow time distributions obtained as described in the first paper of this series (1), using thermal death-time characteristics appropriate to the micro-organisms of greatest importance. The calculations are carried out using the data obtained for the plant described in the previous paper, and they provide an estimate of the bactericidal effectiveness to be expected from that plant.

Comparison of Two Models for Process Holding Time Calculations: Convection System

1985 ◽  
Vol 48 (4) ◽  
pp. 359-363 ◽  
Author(s):  
B. MANJI ◽  
F. R. VAN DE VOORT
Keyword(s):  
Kinetic Parameters ◽  
Actual Process ◽  
Correct Process ◽  
Chemical Systems ◽  
Death Time ◽  
Thermal Death ◽  
Microbial Destruction ◽  
Thermal Death Time ◽  
Relationship Of ◽  
The Relationship

The reaction kinetics of microbial destruction in food products are generally determined by the Thermal Death Time method (TDT), while chemical changes have traditionally been calculated by the more widely accepted Arrhenius approach. These two methods do not reconcile mathematically, and simply stated, one is the inverse of the other. It was of interest therefore to consider the relationship of these methods relative to each other on a mathematically simulated and experimental basis. The kinetic parameters of Saccharomyces uvarum were determined experimentally and used to calculate simulated processes in accordance to the relationships dictated by the TDT and Arrhenius models. The simulation results indicated a discrepancy between the methods, the Arrhenius approach requiring about 16% more time to complete a process. Based on five processing trials carried out using S. uvarum the actual process times were compared to those predicted by the TDT and Arrhenius methods. The Arrhenius method predicted the correct process times on the average, while the TDT predictions were short by about 8% in terms of time. From a microbiological standpoint, these differences are not likely to be singificant, however, they may be important if the TDT method is used to characterize the kinetic parameters of more rigerously defined chemical systems.

Thermal Inactivation of Escherichia coli in Camel Milk

2003 ◽  
Vol 66 (9) ◽  
pp. 1708-1711 ◽  
Author(s):  
SHLOMO SELA ◽  
RIKY PINTO ◽  
UZI MERIN ◽  
BARUCH ROSEN
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Bovine Milk ◽  
Milk Composition ◽  
Camel Milk ◽  
E Coli ◽  
Death Time ◽  
Thermal Death ◽  
Milk Industry ◽  
Thermal Death Time

Camels subsist and produce milk in desert pastures not utilized by other domesticated herbivores. Developing the camel milk industry can improve the economy of desert inhabitants. To comply with sanitary ordinances, camel milk is pasteurized by procedures specified for bovine milk. It is widely accepted that milk composition might affect bacterial thermal death time (TDT). Camel and bovine milks markedly differ in their chemical composition, yet data regarding TDT values of bacteria in camel milk is missing. As a first step toward developing specific heat treatments appropriate for camel milk, TDT curves of Escherichia coli in artificially contaminated camel and cow milks have been compared. Heating the milks to temperatures ranging from 58 to 65°C yields similar thermal death curves and derived D- and z-values. These findings suggest that, in this temperature range, E. coli might behave similarly in bovine and camel milk. Additional TDT studies of various pathogenic species in camel milk are required before establishing pasteurization conditions of camel milk.

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