Guide to Inspections of Low Acid Canned Food 20
Manufacturers - 2
controlled by the microprocessor. This may require observation of the system through several thermal process cycles. The investigator should determine who is responsible for programming the system, how the system is programmed, the name and number of programmable functions, if the programming functions are password or otherwise protected and who is responsible for record review and process verification.
It is also important to determine if the operator has the ability to override any of the computer control functions. If operator override of computer functions are possible, details on how this is done, what overrides are possible, and how this is reflected in the thermal process record should be determined.
The investigator should determine how the system handles process deviations during thermal processing. If the computer system is able to calculate new processes or chose alternate pre-programmed processes the investigator must determine the parameters for computing or selecting the alternate process.
During inspections where microprocessor or computers are being used to control thermal processes in retorts the investigator is required by the Domestic Acidified and Low-Acid Canned Foods, Compliance Guidance Program to determine at a minimum:
- The equipment specifications for software and hardware.
- The critical factors that are controlled by the system.
- How the critical factors are controlled.
- How does the firm ensure that the microprocessor or computer is indicating the correct information (validation).
- How, and how often is the equipment calibrated and/or checked for accuracy.
The references "Guide to Inspection of Computerized Systems in Drug Processing" Feb. 1983, U.S. Dept. of Health and Human Services, Food and Drug Administration and "Software Development Activities" July, 1987, U.S. Department of Health and Human Services, Food and Drug Administration, should be used as guides to inspecting firms using complex computer controlled retort systems (these guides are currently undergoing revision). DEIO also has in process 'Guide to Inspection of Computerized Systems in the Food Processing Industry.
An example of a parameter that could be under digital electronic control is pressure in a retort, which is normally controlled by adding or releasing air from the retort. A common method for pressure control is the use of a pressure sensor to transmit a signal to a pressure controller. The pressure controller will then send signals to position the air supply and pressure release valves. Control of pressure through addition and release of air allows for a more uniform pressure control in the retort. The valves used in pressure control may be pneumatic, electric or a combination of these types. Control of other factors critical to the proper operation of the retort system, such as water level in water immersion retorts, water circulation in cascading & spray water systems, and RPM's in agitating retorts may be monitored and controlled by a variety of methods, including mechanical, electrical and combination systems.
It is important to remember that the system used must provide assurance that the retort system is operating in a manner that the scheduled process will be delivered to the lacf.
Note: If the firm is using a computerized system for record keeping, and/or determining or selecting new processes in the case of process deviations, determine if the system has been reviewed and determined by CFSAN (in writing), to be sufficiently equivalent to a record system generated manually, to meet the intent of the regulations. See the 'Computer Generated Record' section of this guide for additional information.
A variety of valve types may be used on retort systems including:
- PLUG COCK VALVE - This valve consists of a tapered plug with a vertical slot which fits into a tapered valve body. Full flow is obtained when the opening in the tapered plug faces in the direction of flow. When the plug is rotated a quarter of a turn, flow is stopped. Opening and closing the valve is usually accomplished by using a wrench or lever applied to the valve stem. Plug cock valves are noted on retort bleeders and may be used on retort vent lines.
- GATE VALVE - Gate valves are full flow valves normally used to start or stop flow. A gate (sliding shut-off wedge) within the valve body is raised and lowered through a set of threads on the valve stem. The valve is operated by turning the valve stem counter clockwise to open the valve and clockwise to close the valve. These valves are usually either fully open or fully closed during service. When fully open the gas or fluid flows through the valve in a straight line with very little resistance to flow. This feature makes the valve ideal for use in the vent lines of steam retorts, where rapid removal of air may be