Evaluation Of Effectiveness Of Sanitation Systems

As with other important aspects of safe and wholesome food production, sanitation programs require regular evaluation of their effectiveness as part of a specified quality assurance system. Traditionally, this has been undertaken on two levels—an immediate assessment of the performance of a sanitation program by sensory evaluation and a historical measurement of microbial surface populations if surfaces are visibly clean. Sensory evaluations are used as a process control to rectify immediately obviously poor sanitation. Bacterial evaluations may be used to optimize sanitation procedures and ensure compliance with microbial standards and in hygiene inspection and troubleshooting exercises. Recently, rapid methods have been developed to assess microbial surface populations in a time relevant to process control and in this context, only techniques that provide estimates in less than 15-20 min are considered.

As with the inherent faults of end product analysis in describing production quality, reliance should not be placed on assessment techniques that can only sample a very small proportion of plant surfaces. Assessment techniques should, rather, be designed to monitor the effectiveness of an integrated HACCP-type (Hazard Analysis and Critical Control Point) approach to sanitation in which such critical control points may include detergent and disinfection concentration, solution temperature, application procedures, and chemical stock rotation.

Sensory evaluation involves visual inspection of surfaces under good lighting, feeling for greasy or encrusted surfaces, and smelling for product and/or offensive odors. If these assessments indicate the presence of product residues, no further analysis is required and microbiological examination will be misleading. If no product residues are detected, microbiological techniques may be applied. All of the microbiological techniques appropriate for food factory use involve the sampling of microorganisms from contaminated surfaces and their culture using standard agar plating methods. Microorganisms may be collected via cotton or alginate swabs (after which they are resuspended by vortex mixing or dissolution), water rinses for larger enclosed areas, or directly using agar contact plates. Traditional techniques have been reviewed (32,34) since which time few improvements have occurred other than with contact methods which are now available commercially as premade sampling units.

Traditional microbiological techniques all require a minimum of 24-48 h to provide results and these only provide a historical view of the efficiency of sanitation programs. Rapid methodology was devised to ascertain sanitation efficiency and for some products, when to clean, in a time relevant to process control. The two most common techniques are epifluorescent microscopy and the ATP technique. With epifluorescent microscopy, microorganisms may be sampled by swabbing and filtering the resuspension media or filtering rinses (direct epifluorescent filter technique, DEFT) or by enumerating the surface of coupons attached to product contact surfaces (direct epifluorescent microscopy, DEM). After swabbing, estimates may be made of soil and/or microorganisms by analysis of total or microbial adenosine triphosphate (ATP) levels. ATP bioluminescence provides a reliable and rapid alternative to traditional microbiological methods (35). The efficiency and flexibility of this method makes it a unique hygiene-monitoring system for food plants (36). A recent study by Green et al. (37) showed that cleaning agents and sanitizers can affect ATP bioluminescence measurements differently. Consequently, it is important to select carefully the type and concentration of chemical cleaner or sanitizer used to clean the processing equipment when using this method to monitor hygiene. In the majority of practical applications, where an assessment of cleaning is required, analysis for total ATP is preferred on the assumption that any residues, soil or microorganisms, should have been removed. The use of DEM and DEFT has been described for assessing open surface hygiene (12,38), rinses (39), and the use of ATP (40,41).

The accuracy of a range of surface hygiene assessment techniques as compared to the most accurate method, DEM, has been described (42), and is shown in Table 4. The table shows the ability of a number of commercial contact, self-prepared (DIY) contact, traditional swabbing and rapid techniques (ATP and DEFT) to predict a DEM count of 104, 106 and 108 bacteria/cm2. The results indicate that only above 106 bacteria/cm2 are these methods accurate and they are therefore useful for indicating gross contamination only. For cotton swabs, the most widely used method in practice, a result of zero is more likely than a result of 104 when assessing surface populations of 104 bacteria/cm2. The rapid methods available are at least as accurate as traditional methods and as shown in Table 5, which compiles a range of attributes for typical assessment methods, the choice between rapid and traditional techniques is a balance of cost and speed of result.

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