Destruction and injury of Escherichia coli during microwave heating under vacuum

Abstract

Aims: To study the effect of 2450 MHz microwave radiation under vacuum (vacuum microwave or VM) on survival and injury of Escherichia coli and to search for possible nonthermal effects associated with VM. Methods and Results: Destruction kinetics of E. coli in peptone water were determined in a continuous-flow vacuum system, heated by convection heating in a water bath or with microwaves (VMs). Vacuum was used to control the boiling point of water and to maintain temperature in the bacterial suspensions at specified levels (49-64°C). Conclusions: z-Value in the water bath treatment was 9AE1°C while for VM at 510 and 711 W it was 6AE2 and 5AE9°C, suggesting that E. coli is more sensitive to temperature changes under microwave heating. Arrhenius calculations of the activation energies of the destruction reactions suggest that the mechanism of destruction in VM may be different from that of conventional heat. The number of injured micro-organisms showed no significant differences among treatments. Significance and Impact of the Study: The impact of temperature on E. coli destruction was different when microwaves were the medium of heat transfer, suggesting the existence of factors other than heat contributing to the lethal effect of VM.

Use of microwave processing to reduce the initial contamination by Alicyclobacillus acidoterrestris in a cream of asparagus and effect of the treatment on the lipid fraction

“…Microwave sterilization has been proposed and applied for a variety of foods, like fresh pasta, bread, prepared meals, and vegetables (Lau & Tang, 2002;Sun, Tang & Powers, 2007;Yarmand & Homayouni, 2009); moreover, it is well known that it is effective against a wide range of microorganisms, including Escherichia coli (Apostolou, Papadopoulou, Levidiotou & Ioannides, 2005;Yaghmaee & Durance, 2005), Staphylococcus aureus (Yeo, Watson, Stewart-Tull, & Koh, 1999), Bacillus spp. (Celandroni et al, 2004), Campylobacter jejuni (Uradzinski, Szteyn, Gomolka, Jozwik, & Radkowski, 1997), Pediococcus spp.…”

Microbiological comparison of microwave and traditional thawing processes for poultry meat

“…Microwave (MW) irradiation has become increasingly popular in food processing, to brown, dry, cook and particularly in improving food quality and shelf life, despite the lack of official technical criterion (Yahmaee and Durance, 2005;FDA, 2006;Taher and Farid, 2011;Lin et al, 2014).…”

Sterilization of bone allografts by microwave and gamma radiation

“…Th e eff ectiveness of microwave for destruction of microorganisms in various foods has been well established. Microwave treatment has been shown to be eff ective in the destruction of bacterial vegetative cells of S. faecalis , S. aureus , E. coli , Salmonella spp., Listeria spp., Proteus mirabilis , P. aeruginosa (Koutchma et al 2001, Yaghmaee andDurance 2005), bacterial spores of B. subtilis , B. stearothermophilus , B. licheniformis , Clostridium sporogenes (Silva et al 2006, Kim et al 2009), yeasts like Candida albicans , Saccharomyces cerevisiae (Campanha et al 2007) and viruses (Elhafi et al, 2004). Microwave treatment has been reported to cause protein denaturation and aggregation in cytoplasm as well as to induce heat shock proteins, which may cause microbial inactivation.…”