The performance of rapid methods, alternative to the traditional microbial detection methods for monitoring hygiene in red meat abattoirs, was assessed both under experimental (laboratory and abattoir) and commercial conditions.  The methods assessed were based on the detection of protein residues (using the commercially-available products "Pro-tect" [photograph 1] and "Flash sticks" [photograph 2]), total ATP (the Lightning II and Hygiena Snapshot swabs [photograph 3]) and porphoryn (a chlorophyll derivative present in the faecal material of animals fed on a diet rich in plant material; detected using a hand-held VerifEYE Solo). Microbiological testing (total aerobic viable counts; TVC and Enterobacteriaceae) was also carried out on the carcasses and surfaces to provide a general background of hygiene against which the performance of the test methods could be assessed.

 

Photograph 1: The liquid in the left side of the Pro-tect swabs changes colour from green to purple dependent on the concentration of protein residue on an environmental surface

 

Photograph 2: The pad on the end of a Flash stick changes from yellow to blue when exposed to protein residues on an environmental surface

 

	Photographs 3: ATP detection involves the the use of a luminometer to measure how much light is produced from the contamination present on an environmental surface

     An initial lab-based investigation was undertaken to assess each of the alternative methods under controlled conditions, and to identify any potential problems with the practical use of these methods. The VerifEYE Solo was found to be easy to operate.  Optimal performance was observed at a distance of 16mm from the target surface. A range of surfaces found commonly within the abattoir were assessed for the ability to fluoresce as fluorescence can interfere with the detection of faeces by the machine.  Objects such as abattoir wall cladding were found to fluoresce, and the background colour of the surface was shown to have an effect on the reading obtained by the VerifEYE Solo. Diluted faeces were more readily detected than faecal smears, particularly when the faecal smears had dried. Faecal spots as small as 0.3mm could be detected using the system.  However, pig faeces, sourced from a number of different farms, did not fluoresce under the VerifEYE Solo system

    The performance of the same detection methods were assessed at Bristol University experimental abattoir during normal processing conditions.  Chlorophyll solutions were used to assess the practical effectiveness of the VerifEYE system.  Chlorophyll “contamination” was tracked from the hides/fleece/skin of the cattle, sheep and pigs, to the resulting carcasses.  TVC and numbers of Enterobacteriaceae were also determined from the coats and carcasses of the animals.  Surfaces within the abattoir were also monitored using each of the different methods, including the traditional microbiological tests, both before and after routine cleaning.   A correlation between the total ATP and both protein detection methods was observed from the environmental surfaces associated with slaughter of all three animal species.  A correlation was also observed between the total ATP, Flash protein method and the TVC counts with the surfaces related to cattle slaughter.  Transfer of bacteria from the coat/skin of the animal to the carcass was similar in the animals as the transfer of chlorophyll.  Transference of bacteria from coat to carcass was lowest for sheep when compared with the other two species. These findings are strongly indicative that monitoring of the transfer of bacteria to the carcass gives a good indication of the cleanliness of the dressing procedure for red meat animals. Under controlled conditions in a laboratory or experimental red meat plant, the detection of porphoryn (faeces) on sheep and cattle carcasses using the VerifEYE Solo and the detection of protein and total ATP on environmental surfaces were assessed favourably as monitors of process hygiene in red meat abattoirs

    The final assessments were undertaken to examine the performance of the test methods on carcasses (cattle and sheep only) and surfaces (cattle, sheep and pigs) within commercial abattoirs. In order to carry these out, three commercial abattoirs were visited and carcasses sampled on four sites immediately prior to chilling. The surfaces were assessed both before and after routine cleaning. Assessment of the sheep carcasses indicated a potential correlation between the Enterobacteriaceae count and the VerifEYE Solo readings as both methods indicated the brisket area on the carcass to be the most frequently contaminated. No such correlation was observed when the data from the cattle carcasses was examined. The VerifEYE Solo readings from the carcasses were found to give a good overall indication of process hygiene as a whole with both cattle and sheep carcasses, but did give an indication as a potential use for assessing faecal contamination at individual sites for sheep carcasses

    Analysis of the abattoir surface data indicated that the VerifEYE Solo did not detect significant levels of faecal contamination and therefore was not well suited to assessing the hygiene of surfaces. However, the other methods tested did show some strong relationships between each other when used to determine cleanliness of the surfaces, particularly in the sheep and pig plants. Both protein detection methods used were able to detect that effective cleaning had taken place within the abattoirs, but it was felt that the Flash protein method would be better suited to the abattoir environment. Although more expensive, the measurement of total ATP to determine surface cleanliness was also thought to be a useful method within the abattoir to assess surface cleanliness

    Overall, the results of these studies have indicated that the use of the VerifEYE Solo is a good method to measure overall carcass contamination within red meat abattoirs for cattle and sheep but has limited use for assessing surface cleanliness.  The assessment of surface cleanliness in red meat abattoirs for all red meat species, was most cost-effectively achieved using either of the protein detection methods assessed.