Pulsed Electrical Fields
A pulsed electric field is very high intensity variable electric field through which the food is passed. It is the predominant non-thermal process in use today for acid-based fluids, or fruit juices. Combined with mild heating, it enhances the effectiveness of microbial inactivation and extends shelf life of foods. The pathogens are destroyed through destruction of the cell membranes. Tests have shown anywhere from a five- to nine-log reduction.
Pulsed Light
Pulsed light is a surface irradiation system and not a penetration system. It is primarily useful for surface kill of microorganisms, or for liquids if you can run liquids through as a very thin film. Pulsed light consists of very intense and short flashes of light with wavelengths from UV to NIR, emitted by Xenon discharge lamps. Despite its approval for surface microorganism control in foods by FDA, PL is not yet commercially used, mostly due to the lack of knowledge regarding the critical factors of influence and the inactivation mechanisms.
Ultraviolet
Ultraviolet apparatus may consist of a low pressure mercury lamp surrounded by a coil of UV transparent tubing. The juice being processed can be pumped through the tubing and exposed to UV radiation. The electrical energy is around 34 J/ml and is similar to that for conventional thermal processing. UV processing has the potential to improve the safety and extend the shelf life of some juices while maintaining more of the fresh-like qualities of the cider compared to thermal processing.
High Hydrostatic Pressure Processing
High hydrostatic pressure, in which foods are treated under high pressure, up to 6000 atm, by placing them in a medium, usually water in a thick-walled vessel, and compressing the medium.
Irradiation
Ionizing Radiation
Radiation for the treatment of food is achieved through the application of gamma rays (with Co-60 or Cesium-137 radioisotope), electron beams (high energy of up to 10 MeV), or X-rays (high energy of up to 5 MeV). Radiation principles explain how the gamma rays, e-beams and X-rays interact with matter. These interactions result in the formation of energetic electrons at random throughout the matter, which cause the formation of energetic molecular ions. These ions may be subject to electron capture and dissociation, as well as rapid rearrangement through ion-molecule reactions, or they may dissociate with time depending on the complexity of the molecular ion. Effects of radiation on matter depend on the type of the radiation and its energy level, as well as the composition, physical state, temperature and the atmospheric environment of the absorbing material.
Radio Frequency and Microwave
The use of microwave and radio frequencies to heat food for commercial pasteurization and sterilization in order to enhance microbial safety is discussed here. Although not under FDA regulations, use of microwave technology to enhance microbial food safety in the home is also discussed briefly. Mechanisms of heating food and destroying pathogens, and the validation of industrial processes are also discussed, followed by conjecture on handling deviations during industrial processing. This document summarizes information obtained through published literature and personal contacts with industry, academia, and government.
Cold Plasma
A novel antimicrobial intervention that can eliminate food borne pathogens on produce. Cold plasma technology can be used to treat a variety of surfaces (e.g., oxidation, functionalization) or to deposit or graft thin layer macromolecular structures onto organic and inorganic substrates without altering the bulk properties of the materials
Pressure Assisted Thermal Sterilization
An approach in which high pressure and mild heat are combined to achieve processing temperatures that are customarily used in the preservation (canning) of ambient stable, low-acid food products.
Ultrasound
Presently, most developments of ultrasonic’s (sonication) for food applications are non-microbial in nature. High frequencies in the range of 0.1 to 20 MHz, pulsed operation and low power levels (100 mW) are used for nondestructive testing (Gunasekaran and Chiyung1994). Ultrasonic excitation is being examined for nondestructive evaluation of the internal quality and latent defects of whole fruits and vegetables in a manner similar to the use of ultrasound for viewing the developing fetus in a mother's womb
Supercritical Carbon Dioxide
Supercritical carbon dioxide (scCO2) at greater than 31.1oC and pressures exceeding 7.38 MPa exists in a dense liquid state where the CO2 retains the lower surface tension of a gaseous phase and the increased solubility of a liquid phase. This supercritical state enables CO2 to extract various organic and inorganic molecules while inactivating numerous microorganisms. This technology has been enhanced using a micro porous polypropylene membrane contactor system to saturate pumpable liquids rapidly with dense CO2. The dense CO2 is continuously recirculated without depressurization. The nonthermal process effectively inactivated a wide range of spoilage and pathogenic vegetative microorganisms, fresh juice flavors, economic, and without solvent disposal problems.
