Extreme Heat Resistance Research Articles

Microbial inactivation by new technologies of food preservation

The increasing consumer demand for 'fresh-like' foods has led to much research effort in the last 20 years to develop new mild methods for food preservation. Nonthermal methods allow micro-organisms to be inactivated at sublethal temperatures thus better preserving the sensory, nutritional and functional properties of foods. The aim of this review is to provide an overview of the microbiological aspects of the most relevant nonthermal technologies for microbial inactivation currently under study, including irradiation, high hydrostatic pressure, pulsed electric field and ultrasound under pressure. Topics covered are the mechanisms of inactivation, sensitivity of different microbial groups and factors affecting it and kinetics of inactivation.

Effects of novel peptides derived from the acidic tail of synuclein (ATS) on the aggregation and stability of fusion proteins.

The acidic tail of alpha-synuclein (ATSalpha) has been shown to protect the glutathione S-transferase (GST)-ATSalpha fusion protein from environmental stresses, such as heat, pH and metal ions. In this study, we further demonstrated that the introduction of ATSalpha into other proteins, such as dehydrofolate reductase and adiponectin, renders the fusion proteins resistant to heat-induced aggregation and that the acidic tail of beta- or gamma-synuclein can also protect the fusion proteins from heat-induced aggregation. Interestingly, the heat resistance of GST-ATSalpha deletion mutants, which contain shorter peptides derived from the highly charged regions of ATSalpha, was approximately proportional to the number of added Glu/Asp residues. However, the negative charges in the ATSalpha-derived peptides appear insufficient to explain the extreme heat resistance of the fusion proteins, since polyglutamates appeared to be much less effective than the ATSalpha-derived peptides in conferring heat resistance on the fusion proteins. These results suggest that not only the negatively charged residues but also the specific amino acid sequence of ATSalpha play an important role in conferring extreme heat resistance on the fusion proteins. Furthermore, the heat-induced secondary structural changes and thermal inactivation curves of GST-ATSalpha deletion mutants indicated that the introduction of ATSalpha-derived peptides does not significantly affect the intrinsic stability of the fusion proteins.

Safety Issues for Plasma Derivatives and Benefit from NAT Testing

Manufacturing processes for plasma derivatives are in general highly effective for removal or inactivation of enveloped viruses and the products are safe with regard to the clinically important viruses HIV, HCV and HBV. They are not so effective for the elimination for non-enveloped viruses, especially Parvovirus B19 (B19). A certain risk remains of B19 contamination for some plasma derivatives that is caused, firstly, by the occurrence of highly contaminated donations (up to 1014genomes/ml) and secondly, by the extreme heat resistance and small size of B19 which makes it difficult to remove or inactivate. NAT is a beneficial tool for detection of virus contamination. It is routinely used for the detection of HCV-RNA in plasma pools, thereby preventing the processing of HCV-RNA positive material. NAT assays may also be valuable for testing the removal of viruses during manufacturing. This may be especially important if a virus cannot be tested by infectivity assays.

Water content and size of spore components determined by laser diffractometry

For the first time laser diffractometry was used to obtain the refractive index distribution within individual cells in an aqueous environment, allowing accurate determination of their compartmental water content. For bacterial spores the results demonstrated the existence of a dehydrated protoplast surrounded by a less dehydrated integument, thus accounting for the extreme heat resistance of the spores. In contrast, the presence of a dry wall surrounding a water-rich protoplast was shown in fungal spores.

Water content and size of spore components determined by laser diffractometry

For the first time laser diffractometry was used to obtain the refractive index distribution within individual cells in an aqueous environment, allowing accurate determination of their compartmental water content. For bacterial spores the results demonstrated the existence of a dehydrated protoplast surrounded by a less dehydrated integument, thus accounting for the extreme heat resistance of the spores. In contrast, the presence of a dry wall surrounding a water-rich protoplast was shown in fungal spores.