This study is aimed at the development and application of a convenient and rapid optical assay to monitor the wet-heat resistance of bacterial endospores occurring in food samples. We tested the feasibility of measuring the release of the abundant spore component dipicolinic acid (DPA) as a probe for heat inactivation. Spores were isolated from the laboratory type strain Bacillus subtilis 168 and from two food product isolates, Bacillus subtilis A163 and Bacillus sporothermodurans IC4. Spores from the lab strain appeared much less heat resistant than those from the two food product isolates. The decimal reduction times (D values) for spores from strains 168, A163, and IC4 recovered on Trypticase soy agar were 1.4, 0.7, and 0.3 min at 105°C, 120°C, and 131°C, respectively. The estimated Z values were 6.3°C, 6.1°C, and 9.7°C, respectively. The extent of DPA release from the three spore crops was monitored as a function of incubation time and temperature. DPA concentrations were determined by measuring the emission at 545 nm of the fluorescent terbium-DPA complex in a microtiter plate fluorometer. We defined spore heat resistance as the critical DPA release temperature (T c ), the temperature at which half the DPA content has been released within a fixed incubation time. We found T c values for spores from Bacillus strains 168, A163, and IC4 of 108°C, 121°C, and 131°C, respectively. On the basis of these observations, we developed a quantitative model that describes the time and temperature dependence of the experimentally determined extent of DPA release and spore inactivation. The model predicts a DPA release rate profile for each inactivated spore. In addition, it uncovers remarkable differences in the values for the temperature dependence parameters for the rate of spore inactivation, DPA release duration, and DPA release delay.Bacterial spores are common contaminants of food products, and their outgrowth may cause food spoilage or foodborne illness. They are extremely resistant to heat and other preservation treatments in comparison to vegetative cells. The inactivation of spores requires high temperatures and long heating times, which are costly and detrimental to the nutritional and organoleptic quality of most food products. To minimize the required heat treatment, there is an urgent need in the food industry for tailored preservation procedures, based on models that accurately predict the presence of viable cells at every step of the food production process (6, 41). To assess the required heat inactivation procedure for the most resistant cell type, the bacterial spore, we isolated and classified two food contaminants and developed a rapid and sensitive screening method to determine the heat resistance of their spores.Under nutrient-limited conditions, vegetative cells of Bacillus species undergo the cell differentiation process of sporulation (17, 42). The resulting spores are metabolically dormant and show, besides resistance to heat, resistance to other potentially lethal treatments that include radiati...

The aim of this study was to identify Antarctic microorganisms with the ability to produce cold-active antimicrobial compounds with potential for use in chilled food preservation. Colonies (4496) were isolated from 12 Antarctic soil samples and tested against Listeria innocua, Pseudomonas fragi and Brochothrix thermosphacta. Thirteen bacteria were confirmed as being growth-inhibitor producers (detection rate 0.29%). When tested against a wider spectrum of eight target organisms, some of the isolates also inhibited the growth of L. monocytogenes and Staphylococcus aureus. Six inhibitor producers were psychrotrophic (growth optima between 18 and 24 degrees C), halotolerant (up to 10% NaCl) and catalase-positive; all but one were Gram-positive and oxidase-positive. The inhibitors produced by four bacteria were sensitive to proteases, suggesting a proteinaceous nature. Four of the inhibitor-producers were shown to be species of Arthrobacter, Planococcus and Pseudomonas on the basis of their 16S rRNA gene sequences and fatty acid compositions. It was concluded that Antarctic soils represent an untapped reservoir of novel, cold-active antimicrobial-producers.

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As the baby boom generation ages towards retirement we are set to see a change in population demographics, this change will put increased pressure on the healthcare system unless an alternative is implemented. This paper outlines a survey of assistive technology devices to suit an older person in an aging in place situation, in doing so we will be investigating a number of assistive technology devices, both currently available and proposed. This paper also aims to classify assistive technology devices to facilitate future research and development in this area.