Radiofrequency (RF) heating was investigated as an alternative to cooking, drying or chemical disinfection for the preservation of fishmeal and shown to be a highly effective process without any detectable effects, particularly on proteins, lipids or in vivo digestibility. The uniform and deep penetration of RF waves resulted in rapid and homogeneous heating allowing ∼4 times lower thermal loads to be used for >5 log 10 (>99.999%) reduction in infection levels for Salmonella spp and for Escherichia coli O157:H7. Simultaneously, the natural flora was reduced by >3 log 10 (>99.9%). The RF process can be operated in the 70-90 • C range and with high energy-use efficiency (∼50%), which compares well with the 10-15% efficiency for conventional surface heating methods. Industry and expert laboratories confirmed these results. RF heating is thus a new alternative thermal process that is particularly appropriate for disinfecting fishmeal or for reprocessing it rapidly and efficiently with full retention of its natural attributes.
Physical manipulations generating cycles of expansion and compression forces were combined with low vapor concentrations of natural disinfecting chemicals to disinfect and disinfest simultaneously and rapidly fresh agricultural products. Lethality in various fungi, plant and human pathogens and in all biological stages of selected arthropods was demonstrated with fresh fruits and vegetables. The combined process modifies the respiratory metabolism, affects biological structures, causes displacement of the O 2 /CO 2 gaseous equilibrium and induces chemical toxicity at the cellular level. In aerobic microbes, oxygen metabolism is rapidly disrupted, causing biocidal effects. In larval, pupal and adult insect stages, irreversible structural damage of the tracheal system prevents the formation and causes the elimination of air reserves. In arthropod eggs, damage in essential structural features and dehydration of the chorion affect their ability to diffuse and use oxygen. The MSDD process is rapid (<4 h), effective (100% insect controls, >5 log 10 microbial reduction), reproducible, practical, economically competitive and applicable to large volumes of commodities. It causes minimal or no sensory/functional effects in host commodities. If developed commercially, it can be a single alternative to a broad spectrum of postharvest pesticides for disinfection and a likely alternative to methyl bromide fumigation or to irradiation for the post-harvest control of arthropods.
Radiofrequency (RF) power was investigated as a new, physical (nonchemical), thermal process to disinfect wastewater from dairy and animal facilities. Samples (n = 38) from 8 dairy, 2 calf, and 3 swine facilities in California were collected over a 3-yr period and characterized for their dielectric properties, chemical composition, and suitability for thermal processing using RF power. To establish efficacy for disinfection, selected samples were inoculated with high levels (10(6) to 10(9) cfu/mL) of bacterial pathogens such as Salmonella sp., Escherichia coli O157:H7, and Mycobacterium avium ssp. paratuberculosis and processed with an RF prototype system. The capabilities of RF power as a method for thermal disinfection of wastewater were demonstrated when bacteria pathogens were completely and rapidly (<1 min) inactivated when temperatures of 60 to 65 degrees C were achieved. Furthermore, RF technology can be used for large-scale, batch or continuous and portable applications, allowing significant improvements in energy-use efficiencies compared with conventional thermal (surface heating) technologies. Therefore, RF power has potential as an alternative to disinfect dairy/animal farm wastewater before recycling.
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