Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...
Reexamination Certificate
2001-12-18
2004-09-07
Till, Terrence R. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact with electrical or electromagnetic...
C422S001000, C422S038000, C422S040000, C422S044000, C422S292000, C422S300000, C422S307000, C426S231000, C426S237000
Reexamination Certificate
active
06787105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
A process and apparatus is provided for the reduction of microorganisms in a conductive medium using low voltage pulsed electrical energy.
2. Description of Related Art
Reduction of microorganisms in a medium using electricity has been studied for many decades. Most early efforts focused on the reduction of microorganisms in a medium by passage of a high voltage electric current through the medium to generate heat, thereby killing the microorganisms in the medium by pasteurization. The conductive medium was often a pumpable food or beverage, such as milk or water.
Later efforts focused on the reduction of the microorganisms by so-called “nonthermal” pasteurization methods. These methods involve application of a high voltage electric field to the medium in short pulses. The high voltage electric field generates an applied energy of 150 joules/ml or greater and causes death of the microorganisms by electroporation or lysis of the microbial cell membrane. The shortness of the pulse duration attempted to minimize heating of the medium. However, these methods suffer from numerous disadvantages, especially when applied to pumpable foods and beverages. For example, the high voltage electric field when applied to pumpable foods and beverages can cause structural alterations in the food or beverage, adversely effecting the taste and texture of the food or beverage. In addition, such high applied energies are believed to cause the formation of free radicals in foods and beverages, which compounds are considered to cause or promote cancer. Further, the equipment necessary to generate such high applied energies requires an electrical energy on the order of 100 kV/cm. Furthermore, such methods do not appear to kill all types of microorganisms, such as molds and yeast.
Experiments have been conducted in the prior art using low voltage electric fields. However, these electrical energy applications were considered to be unsatisfactory because they were not deemed to cause irreparable damage to the microorganisms.
As examples of the prior art, reference is made to the following U.S. patents, whose teachings are incorporated by reference: U.S. Pat. No. 4,917,785; U.S. Pat. No. 4,957,606; U.S. Pat. No. 5,026,484; U.S. Pat. No. 5,037,524; U.S. Pat. No. 5,464,513; U.S. Pat. No. 5,514,391; U.S. Pat. No. 5,630,915; U.S. Pat. No. 5,766,447; and the following publications: Bai-Lin Qin et al., “Inactivating Microorganisms Using a Pulsed Electric Field Continuous Treatment System”,
IEEE Transactions on Industry Applications
, Vol. 34, No. 1, January/February 1998; Karl H. Schoenbach et al., “The Effect of Pulsed Electrical Fields On Biological Cells”, paper presented at EPRI/Army PEF Workshop II, Chicago, Ill. on Oct. 10-11, 1997; K. H. Schoenbach et al., “Effect of Pulsed Electric Fields on Micro-organisms: Experiments and Applications, paper presented at EPRI/Army PEF Workshop II, Chicago, Ill. on Oct. 10-11, 1997; and Karl H. Schoenbach et al., “The Effect of Pulsed Electric Fields on Biological Cells: Experiments and Applications”,
IEEE Transactions on Plasma Science
, Vol. 25, No. 2, April 1997.
SUMMARY OF THE INVENTION
The process of this invention improves on the prior art by providing a method of microbial reduction in a conductive medium which affects the target microorganism(s) without causing detrimental effects to the medium. The term “reduction” is used in its conventional sense in the art to mean that the method results in mortality to some or all target organisms. In other words, after treatment with the method of this invention, the treated medium contains a substantially decreased number of viable microorganisms. Applications include conductive mediums such as pumpable foods, beverages, processing fluid streams, blood, water, and eco-system waters, as well as conductive solids and solids suspended in liquids or gases to include air, which mediums are microbiologically infected and capable of causing harm to those consuming or coming in contact with the infected medium. The term “pumpable foods” means any food which is capable of being pumped or conveyed through pipes or conduits, including solid food items conveyed in a conductive aqueous solution. Examples of solid food items in this later category are fruits and vegetables. Conductive solids means any solid item capable of being pumped or conveyed through pipes, conduits or channels. Examples in this category are powderized materials. Suspended solids means any solid suspended in a liquid or gas. Examples in this category are food items in carrier liquids or volatile suspended solids in a wastewater facility.
The method of this invention involves the application of low voltage pulsed electrical energy having defined voltage, frequency and pulse waveform characteristics to the target microorganisms in the medium. By the term “low voltage pulsed electrical energy”, it is meant that the combination of energy, frequency and pulse waveform applied to the microorganisms must be such that no free radicals are formed, no ionizing radiation is created, and no osmotic shock waves are formed. The term “low energy pulses” which is used herein by the inventor has the same meaning. It is surprising that the low energy pulses result in cell mortality, since the energy pulses are too low to cause electroporation or lysis of the microbial cell membrane. The specific mechanism by which the method of this invention causes mortality of the microorganisms is not clearly understood. One theory is that the low energy pulses of specific voltage, frequency and pulse waveform cause a disruption in an essential component of the intricate cellular machinery of the microorganism, such as a disruption of the metabolic and/or respiration cycles of the target microorganism. Regardless of exactly how the method of this invention operates to cause mortality to microorganisms, the inventor has demonstrated through extensive experimental tests which are summarized herein that the method is surprisingly effective. Accordingly, when the method is applied with the proper know-how described herein, the ordinary skilled person can achieve substantial reductions in target organisms in a conductive medium by application of low energy pulses which do not have detrimental effects on the medium. As an example of detrimental effects to a medium, there is mentioned the occurrence of organo-leptic changes to a medium which is a pumpable food or beverage.
The effective voltage, pulse frequency and waveform characteristics of each target organism are unique, and therefore the process requires the ability to vary the frequency of energy delivery as well as to vary the voltage applied, with a limitation being such that no combination of applied voltage, pulse frequency and waveform applied is capable of creating structural membrane alterations of the target organisms, e.g., electroporation or lysation of the target organism. Additionally, the combination of energy, pulse frequency and waveform applied must be such that no free radicals are formed, no ionizing radiation is created, nor osmotic shock waves formed. Further, there is substantially no temperature increase or pressure increase.
This process improves on the prior art of disinfection by affecting only the target organism, not the medium. This is accomplished by the controlled release of pulsed energy into a treatment space, such as a conduit or chamber. The process and apparatus may provide for multiple treatment spaces in continuous parallel or series flow paths. The process and apparatus may be installed in a continuous flow production line or in a container, such as a batch storage tank.
The combination of voltage, pulse frequency and pulse waveform are refined such that the energy applied to the target organism disrupts the respiration and/or metabolic codes of the target organism thereby killing the organism. As metabolic and respiration codes are required for living organisms to function, disruption of the codes cause the elimination of the reproductive cycle and de
Chorbaji Monzer R.
Till Terrence R.
Wenderoth , Lind & Ponack, L.L.P.
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