It has previously been known that electrical pulses can be used to provide antimicrobial treatment for food products. Prior food treatment systems include batch mode and flow-through processors. The processors contained first and second electrodes which were charged to high voltages. The high voltage electrodes create high electrical field strengths across a space extending between the electrodes. Field strengths of 5-100 kilovolts per centimeter have been reported.
The processes of the prior art are indicated for use in applying pulsed electric fields to juices, liquid egg products, and other types of pumpable foods. In such systems the electrical treatment is combined with a heat treatment to improve microbial inactivation. This approach in essence combines heat pasteurization with electrical pulse treatment to inactivate microbial populations. However, the use of heat processing necessarily has significant and sometimes derogatory effects upon the taste, color, and other properties of the resultant food products. Thus there is a need for improved processes which do not require combined elevated heat treatment and electrical pulse treatment to accomplish suitable inactivation of microbes.
Prior art electrical pulse treatment systems have also been flawed in having processing chamber designs and methods which result in accumulations of materials such as organic molecules upon the electrodes. Such accumulations can cause fouling of the processor flow channels. More typically, the fouling will affect the properties of the electrical field emanating from the electrodes and their interaction with the fluid being processed. This can lead to non-uniform pulse distribution into the product, which in turn can result in inadequate microbial inactivation. Fouling of processor electrodes can also result in increasing heat buildup at the electrodes. This heat buildup further exacerbates the fouling of the electrodes.
Prior art systems have also utilized exponentially decaying wave forms for the electrical pulses supplied to the electrodes. Such exponentially decaying pulse shapes fail to fully utilize the energy being supplied in a manner which is effective at inactivating the microbes. The prior art systems further have generally used pulse generators which are relatively expensive to build and operate. This has been a drawback to adoption of electrical pulse treatment of food products.
Prior art pulsed electrical field food processors have also been used primarily for liquid food products which flow or can be pumped. The treatment of solid and semi-solid foods poses additional complexity with regard to possible microbial inactivation. The increased difficulty in treating solid and semi-solid foods using pulsed electric fields is believed to in part be due to the presence within such foods of large numbers of various ionic species. The number of ionic species also reduces the resistivity of the food making treatment using pulsed electric fields more difficult.
Thus there remains a need for an improved food processor which can effectively inhibit microbial growth within food products without adversely affecting the taste, color, appearance, and smell of the food product being treated. Other objects and advantages will be indicated in the remaining text of this document.