Faecal & Viscera Contamination on Meat
Faecal contamination is the primary vector for bacteria on meat on the slaughter line of meat processors. As the pelt is removed from the carcass, faeces can sometimes come into contact with the exposed carcass and is often attached to wool or hair. Also, during evisceration, leakage of the viscera may contaminate the carcass. The faecal contamination contains a significant quantity of bacteria. The bacteria can be either pathogenic (such as E. coli) or spoilage bacteria, both of which cause major problems in the meat supply chain. Pathogenic bacteria on meat cause serious illness, hospitalisations and deaths when consumed. Spoilage bacteria cause significant product losses and shortened shelf life, leading to billions of dollars of wasted meat annually. Some countries are implementing zero faecal tolerance policies (e.g. US and China). In these countries meat is inspected at the boarder for visible signs of faecal contamination. If any contamination is detected the shipment may be rejected and the meat processors licence to import into the country is suspended or removed. They also test for E. coli, which is typically introduced through faeces. It is very costly for the meat company if a shipment is detected with contaminants. Sensitive and rapid faecal detection systems would benefit meat processors, inwards goods and boarder control inspectors, by assuring meat products are not contaminated with faeces.
Existing Practice for Faecal Detection
The current practice for faecal detection is visual inspection, which is costly to perform and must be performed quickly on the slaughter line. Visual inspection gives variable results at best and is typically unreliable. Also, much of the faecal contamination is not visible and therefore cannot be detected with visual inspection. From a legislative perspective, in many countries including New Zealand and the US, government officials (meat inspectors) inspect all meat carcasses and viscera. There may be many meat inspectors working in each processing plant. They inspect the carcass and viscera (intestines) for many anomalies (diseases, deformities, signs of poor farming practices, faeces on the carcasses etc.) They visually inspect every carcass for faecal contamination and ensure that any contamination is removed. Unfortunately, as noted above, this visual inspection is fast and unreliable. Many meat processors water wash their carcasses in the belief that it can remove contamination. However, there is significant evidence suggesting that carcass washing simply spreads the bacteria around the carcass rather than removing it. Figure 1 shows a small piece of fatty surface tissue from a lamb carcass. An area of faecal contamination is visible which the inspector missed. The plant quality assurance person that was hosting a visit to the processing plant detected it as he happened to be next to the particular carcass.
Figure 1. Faecal contamination on lamb carcass surface tissue
Benefits of Faecal Detection
The obvious benefit of faecal detection for meat processors is to help prevent the release of meat contaminated with pathogenic bacteria such as E. coli. Detected faecal material can be located and removed very early in the process, therefore producing a safer product. Another important benefit of faecal detection is to reduce spoilage bacteria on meat products. A long shelf life is important for the entire supply chain of meat products. By reducing spoilage bacteria from faeces, meat processors can gain a significant improvement in shelf life for the products, therefore increasing the value of their products for themselves and their customers. Compliance with the Zero Faecal Tolerance policy that is implemented in countries such as the US and China is a challenge that a faecal detector can help meet. By implementing a thorough faecal detection system and processes will ensure that meat processors can confidently meet the expectations of Zero Faecal Tolerance policies. The rapid feedback from faecal detection systems is a valuable tool for auditing and training to ensure that the faecal contamination is minimised at the very early stages of meat processing. It may also be used at boarder inspection sites, process sites and cool stores.
How does faecal detection work?
Faecal contamination is detected by illuminating the natural fluorophores (mostly chlorophyll) of the faeces with blue light and measuring the fluorescence. This is achieved contacting the meat. Roughage eaten by animals (grass, straw, silage etc.) contains chlorophyll. The chlorophyll and its metabolites in faeces have a very strong fluorescence signature, with a large peak at approximately 670 nm (see Figure 2). When meat is contaminated with faeces, it is the 670nm peak that is detected (see Figure 3). However, components of meat also fluoresce, making the detection of faeces difficult, particularly for low levels of contamination where the fluorescence of the faeces is smaller than the overwhelming meat fluorescence.
Figure 2. Typical fluorescence signature of faeces illuminated with blue (450 nm) light. The chlorophyll peak at around 670 nm is clearly evident.
Figure 3. Fluorescence of fatty surface tissue of lamb meat (blue) and the same meat grossly contaminated with faeces (red).
The constituents on meat vary considerably, depending on the location on the carcass and the surface properties of the meat. The most important meat components from a faecal detection perspective are collagen and fat, which have large and variable fluorescence spectra that may be many times larger than any faecal contamination fluorescence. Therefore, the fluorescence from one piece of meat to another can vary to a very large extent, making reliable detection of faeces difficult. Protoporphyrins are another problem when detecting faecal fluorescence. Protoporphyrins can easily develop on meat after slaughter and light induced Photo-protoporphyrin is a particular problem with an emission peak near to our detection target of 670 nm. To achieve successful detection of faeces, Veritide has developed a detection and analysis algorithm based on a model of meat fluorescence. A priory knowledge of the fluorescing components of meat and faeces are used to build a model to analyse the measured fluorescence. This allows the fluorescence of the faeces to be separated from the meat fluorescence and subsequently quantified. For this method to be successful, fluorescence from sections of the measured fluorescence spectra from outside of the chlorophyll peak must also be analysed so that the fluorescence from the meat constituents can be used to model the meat and then eliminate the meat fluorescence from the chlorophyll fluorescence signal. The level of chlorophyll in faeces can vary considerable, depending on what the animal has been eating. However, the Veritide detection method is capable of detecting very low levels of chlorophyll from the roughage the animals have eaten. Figure 4 shows the fluorescence from primarily grain fed bovine faeces.
Figure 4. Faeces from bovine fed on grain with a small component of silage.
Bacteria and Faeces
The aim of detecting faeces is to detect any faecal contamination rather than the absolute level of contamination. This is because all faeces harbour bacteria and should be removed. Even minute traces of non-visible faeces can contain a significant quantity of pathogenic or spoilage bacteria. The Veritide technology can detect these minute faecal traces that cannot be seen visually, but still contain significant quantities of bacteria. While faeces are known to harbour large amounts of bacteria, faecal detection technology does not directly detect bacteria. Therefore, faecal detection technology cannot identify if specific bacteria species are present.
The model based detection method is very sensitive and specific and has low false positive and false negative detections. Testing has shown that the Veritide technology can reliably detect traces of faecal contamination from up to approximately 500mm from the carcass in typical room lighting conditions, on both a slaughter line and within a cool storage area. A modulated light source and appropriate detection processing is used to eliminate room light interference. There is no known time limit post slaughter that would cause faecal detection to fail. We have identified faecal contaminated on meat after four weeks of refrigeration. We anticipate that the technology could be used by meat inspectors at the boarders of countries that wish to inspect imported meat several weeks after slaughter. Humidity does not affect detection sensitivity unless there is a fog that can block the light to and from the carcass.
BluLine Portable Faecal Scanner User Interface
The user interface of the Veritide BluLine portable faecal scanner is shown in Figure 5. A 10 segment LED bar graph is used to show when faecal contamination is detected. Bright LEDs are used so the scanner can be used in noisy environments of meat processing plants and poorly lit cool storage areas. The lower 7 LEDs are green coloured and the top three are red coloured. The more LEDs illuminated, the greater level of faecal contamination that is detected. The bar graph simply shows the level of contamination and there is no thresholding or minimum detection level of contamination. For best operation the sensitivity of the display can be adjusted with the up and down arrow buttons so that the display illuminates at least the 7 green LEDs when faeces are detected. In this manner the display very obviously shows when any faeces are detected.
Figure 5. Bluline Faecal Scanner Display.
Beef, Lamb, Pork and Chicken
The Veritide faecal detection technology has been successfully deployed in beef and lamb processing plants.
The technology has not yet been tested on pork or chicken. For chicken, the optical filters will need to be changed to suit the different components of chicken faeces. veritide hope to complete trials on pork soon.