Abstract

Microbiological testing is an effective tool for verifying sanitation programs in meat and poultry operations. The objectives of this study were: 1) to determine if line employees, as represented by university students and staff, not only can clean and sanitize processing equipment but also can perform microbiological environmental sampling, which evaluates the sanitation process; and 2) to determine if data from sampling can be analyzed using statistical process control. A 3M Quick Swab and a 15x10 cm template were used to swab facilities and equipment. The swab diluent was poured directly onto one of three 3M petrifilms™ (aerobic plate counts (APC); yeast and molds (YM); or E. coli and coliforms (EC). Samples were collected 14 times over an eight month period resulting in approximately 140 samples total. The APC counts for the clean contact meat surfaces ranged from <0.007 (detectable limit) to 0.68 CFU/cm², respectively, whereas, APC counts for clean facilities/non food contact surfaces and drains ranged from <0.007 to 0.08, and 0.14 to 1.78 CFU/cm², respectively. Overall, the E. coli and coliform counts for clean facilities/non food contact surfaces and drains were <0.007 CFU/cm². The YM counts for clean contact surfaces ranged from <0.007 to 0.127, and <0.007 to 0.21 CFU/cm² for yeast and mold, respectively. Data were analyzed using simple statistical process control tools (individual moving range control charts), thus, allowing the identification of sanitation problems in the plant and development of improvement strategies by students and management. This resulted in decreased counts over time, bringing the process into statistical control. Companies can utilize microbiological testing procedures and link the results to statistical process control techniques to improve the verification of their sanitation programs.

Introduction

Meat and poultry plants are required to prepare and implement site-specific sanitation standard operating procedures (SSOPs) to include cleaning and sanitizing procedures. Processors often rely on visual inspection to determine the effectiveness of their sanitation program. However, this method does not assist processors in appropriately determining if microorganisms may still be present on equipment such as food contact surfaces. Microbiological testing methods verify that the processing facility and equipment have been adequately cleaned and sanitized to control microorganisms.

Objectives

The objectives of this study were:

1. to determine if line employees, as represented by university students and staff, not only can clean and sanitize processing equipment but also can perform microbiological environmental sampling, which evaluates the sanitation process;
2. to determine if data from sampling can be analyzed using statistical process control.

Materials and Methods

Cleaning and Sanitation Procedures:

Students enrolled in the Meats Laboratory course and/or Meats Laboratory staff participated in cleaning and sanitizing the slaughter or processing equipment and areas. Large pieces of bone, fat, and muscle tissue were first removed and placed in an inedible container. Equipment was disassembled as needed and rinsed with warm water. The cleaning compound (Futron^® , Pro Chem, Alpharetta, GA) was mixed according to directions and surfaces (cutting and stainless steel tables) and equipment were hand scrubbed. In addition, Futron^® mixed with water was sprayed over equipment, walls, doors, and floors. All equipment and facilities were then rinsed again with warm water; excess water was removed; and a chlorine sanitizer was applied.

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Microbiological Procedures:

Students and staff also collected microbial swab samples during processing and after cleaning and sanitizing. A flat surface was located in either the slaughter or processing room. This included: direct food contact surfaces (cutting tables, band saw, lugs, packaging equipment); non food contact surfaces (paper towel dispenser, soap dispenser); facilities (walls, doors, floors); and drains. Special causes of variation were simulated by deliberately swabbing uncleaned surfaces.

Sample Collection:

To collect the sample, the following procedures were used:

1. The sampling location and date was written on the 3M Quick Swab (3M, St. Paul, MN) label.
2. The swab was hydrated with letheen broth.
3. A sterile plastic template (15x10 cm) was placed on the sampling location by touching only the corner of the template.
4. The template area was swabbed by quickly moving the swab width-wise back and forth along the surface.
5. The swab was placed back in the container with the letheen broth, sealed, and microbiological analyses were conducted.

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Microbiological Analyses:

Microbial tests were randomly selected and the entire contents of the Quick Swab were poured onto 3M petrifilm™ for either aerobic plate count (APC); E. coli and coliforms (EC); or yeast and mold (YM) enumeration. APC and EC petrifilm samples were incubated at 35°C for 48 hours. YM samples were incubated at 25°C for 5 days.

Statistical Analysis:

Microbial counts were analyzed using and not using log(10) transformation. Process stability was determined using individual moving range control chart (XMR). Data were analyzed using "Quality Analyst, Version 5.1" (Northwest Analytical, Portland, OR). For analytical purposes and plotting of graphs, the value of 0 was used when no colonies were observed on films. However, this value is reported as <0.007 CFU/cm² which is the detectable limit. A value of 6.67 CFU/cm² was assigned for counts that were too numerous to count (TNTC).

Results

Overall, the general sanitation procedures showed a stable process. There were two places were the APC counts exceeded the upper control limits, indicating a special cause of variation. The control charts were able to identify non cleaned surfaces from cleaned surfaces when the microbiological counts exceeded approximately 0.4 CFU/cm².

When a log transformation was conducted on the data, all processes were found to be in process control (no special causes of variation were identified). With the exception of the incidence of TNTC, all microbiological results were within a range of three logs. The log transformation of the microbiological data was not as sensitive in identifying sanitation problems.

Figure 1 shows the individual moving range control chart for the cleaned surfaces in the pilot plant. During the first half of the study two test points were shown to be "out of control." Upon investigation, these points were identified as being the gut cart and the vacuum packaging blue board. Efforts were taken to improve the sanitation procedures. These improvements were verified during the time frame of 1/25/01 to 4/3/01.

Figure 1: Individual and moving range (XMR) control charts

Y axis is CFU/cm2 ucl = upper control limit; cl = center line; lcl = lower control limit

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Figure 2 shows the effect of challenging the analysis system. Non clean surfaces were deliberately swabbed and data analyzed. The control charts were able to identify about 25% of the time when a non clean surface was swabbed.

Figure 2: Individual and moving range (XMR) control charts

Y axis is CFU/cm2 ucl = upper control limit; cl = center line; lcl = lower control limit

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Tables 1 and 2 show the general statistical results for the non clean and clean contact surfaces, thus showing the effectiveness of the cleaning procedures. It should be noted that the non clean surfaces had a large degree of variation which is attributed to swabbing actual production surfaces. The APC counts for clean facilities/non food contact surfaces and drains ranged from <0.007 to 0.08,and 0.14 to 1.78 CFU/cm², respectively. Overall, the E. coli and coliform counts for clean facilities/non food contact surfaces and drains were below the detectable limit of <0.007 CFU/cm². The YM counts for facilities/noncontact surfaces ranged from <0.007 to 6.67, and <0.007 to 0.23 CFU/cm² for yeast and mold, respectively.

Summary

Prerequisite programs such as SSOPs are an essential part of a meat processors HACCP system. These programs must be continually verified to ensure effectiveness. Microbiological monitoring programs provide a means to evaluate the SSOPs prerequisite programs. This research demonstrates the following:

1. Simple microbiological environmental monitoring programs are easy to implement and maintain.
2. The monitoring programs provide quantifiable data which can be evaluated using simple statistical process control techniques.
3. The control charts provide plant management with the proper knowledge so appropriate action can be taken with regard to ensuring effective sanitation of the plant and its equipment.

Conclusions

A simple environmental monitoring and analysis system was developed using a combination of 3M quick swabs, petrifilm™, and control charts. This system was easily implemented by university students and staff in an operational meats pilot plant. Thus, it is possible to use simple SPC techniques coupled with simple environmental monitoring techniques to determine effectiveness of plant sanitation programs.

Acknowledgements

The authors would like to thank the students in the Meats Laboratory course; Jonathan Campbell, Meat Laboratory Manager; and Anne-Sophie Lacote, an exchange student from Ecole Superieure d'Agriculture, Angers, France for collecting samples and conducting the microbial analyses.

This paper was presented at the joint meeting of the American Dairy Science Society, American Meat Science Association, American Society for Animal Science, and the Poultry Science Association in June, 2001, Indianapolis, IN.

Author Information

Kelly J. K. Getty
Kansas State University
Food Science Institute
148 Waters Hall
Manhattan, KS 66506-4010
Email: kgetty@oznet.ksu.edu

John G. Surak
Clemson University
College of Agricultural Forestry and Life Sciences
220 Barre Hall
Clemson, SC 29634-0355
Email: jgsurak@earthlink.net

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