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Considerations in building and equipment design can enhance sanitation and prevent cross-contamination.

1. Plant layout – vertical versus horizontal flow 2. Multiple rooms 3. Airflow control

4. Equipment/personnel traffic management 5. Segregate ‘wet” and “dry” areas 6. Plant location 7. Transitions (from room to room and unit operation to unit operation) 8. Minimize product and dust leakage, spi l lage, and accumulation

9. Easy access for inspection and cleaning 10.CIP versus COP

11.Capture/recycle under-processed material

While the above describes areas to focus in building and equipment design, it is also necessary to identify and monitor processing variables which include the critical control points.

1. Assume presence of salmonella in raw material (test for verification) 2. Establish heat, shear, pressure, and time parameters for the process

3. Monitor, control, and document critical process parameters 4. Contain/recycle under-processed material 5. Test to validate effectives of process 6. Develop release program

Research studies have confirmed that a processing step with sufficient mixing can effectively destroy salmonella at log 6 when a minimum product temperature of 77° C and 22% moisture is achieved. An R&D testing environment is not always an option, but the production environment can be a viable validation method even though raw materials may not consistently test positive for salmonella.

Figure 1: Temperatures Required to Kill Various Microorganisms

The temperature/time relationship required to kill various classes of microorganisms is indicated in Figure 1 (2). If sufficient moisture (22%) and mixing are present, relative low product temperatures (77° C) and retention time (a few seconds) at that temperature are required for the destruction of salmonella. The accurate measurement of product temperatures is critical and the following precautions are necessary for the configuration of product temperature sensors (Figure 2):

1. Extend temperature sensor at least 6 mm into product stream – 25mm is preferable 2. Add metal sheath to protect tip of temperature sensor from wear due to product abrasion

3. Insulate where sensor passes through equipment wall 4. Use duplicate sensors 5. Calibrate sensors

6. Locate inboard of extruder die

7. Traceability via chronological chart recorders Figure 2: Proper Location of Product Temperature Sensor

Temperature sensor

Insulation (red)

The majority of the pet food safety concerns today center around microbial contamination. A complete and balanced pet food safety program is required to control and reduce concerns of microbial contamination. Critical control points in pet food processing usually involve product temperature. Product temperature is an important part of a list of process parameters that should be routinely monitored, controlled, and validated. Product temperature can be measured and adjusted rather easily and quickly. Relatively large investments are not typically required for the technology to support this component of processing/manufacturing. Equipment design is also a key contributor to successful pet food safety programs and there exists several innovations in the industry to enhance food safety. Plant and equipment design are not easily changed or quickly modified. Investments into these designs and acquisitions are long term. Functionality and economic evaluations based on life expectancy and return on investment are useful tools in this decision –making process. Example innovations in the areas of product transfer, equipment design and construction, recycling of under-processed materials, and control systems/on-line testing devices are discussed next.


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