John G. Surak PhD Surak and Associates Clemson, SC

Transcription

1 FSIS POLICIES AND GUIDANCE ON STATISTICAL PROCESS CONTROL PROCEDURES IN SLAUGHTER OPERATIONS FSIS POLICIES AND GUIDANCE ON STATISTICAL PROCESS CONTROL PROCEDURES IN SLAUGHTER OPERATIONS John G. Surak PhD Surak and Associates Clemson, SC

2 This document provides information to support the FSIS Outreach seminar on FSIS policies and guidance on Statistical Process Control procedures in slaughter operations FSIS policies and guidance on Statistical Process Control procedures in slaughter operations that was given on December 4, Included this documents are a number of supporting publications that was developed either by FSIS or myself. Included is an Extension Publication from the Clemson University Cooperative Extension Service that describes the use of Statistical Process Control to improve quality and reduce production costs. This publication has a list of references to help you identify excellent texts in SPC. John G. Surak, PhD Surak and Associates Clemson, SC jgsurak@yahoo.com December, 2007

3 Index FSIS policies and guidance on Statistical Process Control procedures in slaughter operations. Appendix A Improving Quality and Reducing Production costs with Statistical Process Control Appendix B 9 CFR Contamination with microorganisms; process control verification criteria and testing; pathogen reduction standards. 07/janqtr/pdf/9cfr pdf Appendix C 9 CFR Contamination with microorganisms; process control verification criteria and testing; pathogen reduction standards 07/janqtr/pdf/9cfr pdf Appendix D Guidelines for Escherichia coli testing for process control verification in cattle and swine slaughter establishments Appendix E Guidelines for Escherichia coli testing for process control verification in poultry slaughter establishments Appendix F Commonly asked question from small and very small plants on statistical process control (2)

4 FSIS POLICIES AND GUIDANCE ON STATISTICAL PROCESS CONTROL PROCEDURES IN SLAUGHTER OPERATIONS FSIS POLICIES AND GUIDANCE ON STATISTICAL PROCESS CONTROL PROCEDURES IN SLAUGHTER OPERATIONS 1 BASICS OF SPC Statistical Process Control or SPC is a powerful tool to help meat and poultry processors improve quality, improve regulatory compliance, and reduce operational costs. It does this by presenting data is a graphical form rather than tabular form. This makes the data easier to interpret and understand. SPC accomplishes these objectives by using a process called Statistical Thinking. Statistical Thinking is more than using control charts to manage a process. It is a management system that sharpens the focus of process thinking. Statistical thinking was developed in 1993 by the Statistics Division of the American Society for Quality. It is composed of the following parts All work is done in a system of inter connected processes All process show variation The key to success to both marketplace and regulatory compliance is the reduction of variation. A process is a series of sequential tasks that has an input, conversion step that adds value to the input, and an output. Inputs can come from internal or external suppliers. The outputs can go to either internal or external customers Figure 1 shows a simplified flow diagram of a beef slaughter operation. The input into this process is the cattle and the output are the carcasses going to carcass fabrication. Also noted on this figure is the place where the carcass is sampled for E. coli Figure 1 Simplified beef slaughter operation 1 This article is intended to provide general information on SPC and not in-depth detail on the use of SPC in process control. If readers want detailed information they are encouraged to study a SPC text. 1

5 Cattle Receiving/holding Stunning/sticking - bleeding Head removal/dehiding Evisceration/Viscera processing Splitting trim rail/final carcass wash Chilling Sampling for E. coli testing Carcass fabrication One tool of Statistical Thinking is Statistical Process Control or SPC (Appendix A). SPC consists of a number of simple tools that allow the meat or poultry producer to manage their processes and take effective actions to adjust and/or improve processes when data indicates that the process has changed. Control charts are the hallmark of SPC. Figure 2 presents a simple control chart. The blue line is a plot of the data versus the time the data were collected. The control chat shows the variation of the measurement over a specific time period. The Upper Control Chart Limits or UCL and Lower Control Chart Limits or LCL provide points of reference on the control chart. They show the maximum variation that can occur when the processes is running at its best and has not changed. The UCL, LCL and Center Line are calculated using actual process data. There are specific formula use to calculate these values. The formula can be found in standard SPC texts or included as part of SPC computer packages.. Figure 2 An example of a control chart UCL Measured Response Center Line LCL Time The control chart can be thought of describing the behavior of a process. The behavior can either be stable or non-stable. A stable process indicates that the process has not changed. There is an indication that the process has changed when a point falls outside 2

6 either the UCL or LCL 2. This is an indication that the process has changed. Most of the unplanned process changes tend to produce either product safety or quality issues. When a process has changed, the process is said to be out of control. When this occurs the establishment should implement the corrective action process which includes ensuring that the product meets performance criteria and determining the root cause of the process change. Once the root cause is determined, effective actions can be taken to ensure that either the problem is prevented or that the chance of reoccurrence is very small. Control charts provide a tool to help eliminate sources of undesirable variation. They provide a starting point where to look in the process for the source of the problem. For example if a control chart that measures E. coli levels in chilled carcasses indicates that the process is out of control or the process has changed, the investigation will start with the chilling step (Figure 1) and proceed up the process until the cause of the problem has been identified. Once that the cause has been identified, effective remediation can be taken to eliminate the cause of the problem. SPC has several critical limitations. The limitations include When a change in the process occurs, control charts do not tell what has changed in the process or where these changes occurred. Establishments need to use good corrective action procedures to determine the cause of the change. There tends to be a loss of effectiveness of control charts to measure process behavior when the manufacturing process has a very low output. There tends to be a loss of effectiveness of control charts if the data being plotted has a large percentage of values equal to zero or in the case of microbiological samples, a large number of values are less than the detectable level for the microorganism. Control charts do not tell if a product is meeting specifications. In fact, a process can be in control and producing product that does not meet specifications or performance standards. If standard control charts are used to monitor a process, establishments must use other SPC and/or QA techniques to determine if a product meets specifications or performance standards. This can occur if the process is producing product with excessive variability. E. coli TESTING The FSIS requires generic E. coli testing, as an indicator organism for fecal contamination, in meat and poultry establishments. The objective of these regulations is to reduce the occurrence of E. coli on carcasses to less than the 80 th percentile that was published in FSIS baseline data studies during the 1990s. The performance standards for maximum E. coli levels are published in two regulations, (9CFT and 9CFR381.94). Performance is defined as acceptable, marginal, and unacceptable. Table 1 lists the performance standards for various species. The sampling rated is defined by the volume of carcasses the establishment processes 2 Most SPC systems use a minimum of four rules to interpret the patterns on control charts. These rules increase the accuracy of the interpretation. In addition, most SPC programs incorporate these interpretation rules into the software, therefore, operators do not need to remember all of the interpretation rules. 3

7 Species Table 1 Performance standards for E. coli levels in carcass Lower Limit of Upper limit of Number of marginal range marginal range samples Maximum number of permitted samples in marginal range Cattle Negative a 100 CFU/cm Swine 10 CFU/cm2 10, CFU/cm 2 Chicken 100 CFU/ml 1000 CFU/ml 13 3 Other poultry b Notes a Negative is defined by the sensitivity of the method used in the baseline study with a limit of sensitivity of at least 5 CFU/cm2 carcass surface area b values will be added upon completion of data collection programs The Agency allows establishments to use a process control chart or a table to record E. coli levels on carcasses. Experience has shown that it is easier for a person to interpret data in a graphical form rather than in tabular form. FSIS developed specific guidelines for the establishments that are classified with small and very small volumes. For small establishments the E. coli levels will be sampled once per week. For very low volume establishments FSIS states sample the predominate species once per week at the beginning of the first full week or operation after June 1 until at least 13 test results have been obtained or the following June 1, whichever is first. The establishment will repeat the same sampling regimen once per year beginning the first full week of period after June 1. If the very low volume establishment is using the excised sample technique and is slaughtering a type of livestock for which performance criteria have been determined, the establishment must continue sampling once per week until the results show that it has met the m/m criteria outlined in the Pathogen Reduction/HACCP regulation. If the performance standard is interpreted as an indication that the establishment may not be maintaining process control to prevent fecal contamination. The establishment should take actions to review process control, discover the cause, if possible and prevent reoccurrence. The regulations also require a written procedure for microbiological sampling that includes the following: Identifying employees designated to collect the sample Specifying the location for sampling, the method used to ensure a random sample. Sampling handling procedures to ensure sample integrity. Records for red meat Test results are recorded in colony units per square centimeter. Test values of less than 1 cfu/cm 2 need to be recorded. Results should be recorded in the order 4

8 of the sample collected including information useful for determining appropriate corrective action when problems occur. These is include date, time of sample collection and slaughter line if more than one line exists. The records need to be maintained for at least 12 months. Records for poultry Test results are recorded in colony forming units per milliliter of rinse. Test values of less that 1 cfu/ml need to be recorded. Results should be recorded in the order of sample collection including information useful for determining appropriate corrective action when problems occur. Such as date and time of sample collection and slaughter line, when multiple slaughter lines are present in the establishment. The records must be kept for 12 months If a sample is lost when it is shipped to an off site lab, or the sample arrives late, or outside acceptable temperature parameters, the reasons for the missing data shall be documented. The Agency developed a control chart method that is designed to assist low and very low volume establishments to plot the E. coli data in control chart form. This method compensates for some of the limitations of the standard SPC techniques. When an establishment elects to use this process, they will use UCLs and LCLs that were defined by FSIS (Table 2). The control chart is interpreted using a 13 period moving window. The moving window works by evaluating the current sample along with the most recent 12 previous samples. Table 2 UCL and LCL for control charts developed using FSIS techniques These control chart limits have been established by FSIS Species LCL UCL Cattle 0 cfu/cm cfu/cm 2 Swine 0.46 cfu/cm cfu/cm 2 Lamb 0 cfu/cm cfu/cm 2 Table 2 Evaluation criteria for interpreting E. coli control charts when the control chart uses the FSIS generated Upper Control Chart Limits and Lower Control Chart Limits Observation on the control chart Interpretation and actions to be taken No more than 3 sample results out of Process is in control 13 are above the LCL More than 3 sample results out of 13 are above the LCL One sample result is greater than the UCL Process is out of control and the establishment should take action to bring the process back into control Process is out of control and the establishment should take action to bring the process back into control The E. coli sampling procedure functions as verification assessment to determine if the establishment is controlling the processes to prevent fecal contamination during the slaughter, evisceration, and chilling processes (Figure 1). Establishments should have other QA procedures that include measurement and verification activities to ensure 5

9 various processes are properly working., This, for example, can include documentation of proper procedures for dehiding and verification that the procedures are being used by the employees. If the proper control measures are developed and maintained, then the establishment can be assured that the carcasses will pass the E. coli verification test. Example Table 3 reports the E. coli levels for a cattle slaughter operation. E. coli samples were taken once per week. Table 3 E coli levels Week CFU/cm The data are plotted on the following control chart (Figure 2). 6

10 Figure 2 3 UCL Cfu/cm Time period LCL First moving window in control Second moving window in control Third moving window in control Fourth moving window In control This control chart shows the results for five moving windows. The process is in control for the first three moving windows. However, during the fifth moving window, there were three samples that were above the LCL. As a result, the establishment should identify the root cause of the problem and take action to bring the processes into control. SPC and CONTINUOUS IMPROVEMENT Fifth moving window Out of control SPC goes beyond verify regulatory compliance to E. coli performance standards. To gain the maximum effect from SPC, it needs to be applied to all parts of the operational processes and to be linked to an effective continuous improvement program. SPC provides a series of problem solving tools that help the processor understand the root causes of problems, thus helping the company develop effective corrective actions. When this is done over a period of time, the causes of waste are eliminated and the establishment achieves improved financial success. 7

11 Appendix A Improving Quality and Reducing Production costs with Statistical Process Control

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