In certain environments, bacterially contaminated pork carcasses are inevitable. The old principle of garbage in, garbage out applies to a meat factory also. One can not make excellent products from bacterially contaminated meat. Good hygiene starts far back in the supply chain. Some thoughts on sanitising pork carcasses.
“After killing and evisceration, most of the microbial characteristics of the carcass remain unaltered. In a healthy animal, it is expected that that inner layers of muscle tissue are free of any contamination from air, soil, and water. However a large number of microorganisms find their way to the carcass surface during the cleaning operations from the intestine and by contact with knives, hooks, walls, floors as well as by human contact (Guerrero and Taylor, 1994). Main sources of bacterial contamination include feces from the hide, hair, and hooves of the animals (Mies et al 1999). During processing, workers and equipment may spread bacterial contamination from the hide to the product. Integration of sanitizing methods, such as knife trimming in combination with other antimicrobial decontamination methods such as steam vacuuming, hot water and acid sprays systems and steam pasteurization can help to improve the microbial safety of carcasses after slaughter (Gorman et al 1995, Castillo et al, 1998, Castillo et al 1999, Pipek et al 2004).
Medynsky, Pospiech,and Kniat (2000) found that an increase of the lactic acid concentration in meat above the level of 0.5% enhanced water holding capacity and reduced thermal loss. In other study Jimenez-Villarreal et al (2003) found that lactic acid treatments on beef trimmings before grinding could improve or maintain the same sensory and instrumental color, sensory odor, lipid oxidation, sensory taste, shear characteristics and cooking characteristics as traditionally processed ground beef patties. Therefore the use of these antimicrobial treatments could be used in industry as a measure of safety improvement without negatively impacting the fresh product. Carcass decontamination utilizing organic acids is a sanitation process that is widely used in the industry, and has been studied deeply. In 1995 (Netten, Mossel and Veld, 1995), found that lactic acid decontamination was capable of eliminating salmonellae from pork, veal and beef carcasses, and that this compound is also likely to be effective against C jejuni. This bacterium is at least 10-fold more sensitive to lactic acid than Salmonella. Furthermore, counts of C. jejuni on freshly slaughtered veal, pork and beef carcasses are also up to l00-fold lower than those of Salmonella. Castillo et al., (1998) compared the effect of different decontamination interventions on E. coli O157:H7 inoculated on beef carcasses. Lactic acid rinses in combination with water wash, trimming and hot water reached reductions from 4.2 to 5.0 log CFU/cm2. Lactic acid is frequently used for beef carcass decontamination. Its ability to reduce pathogens or other organism of fecal origin has been studied extensively showing that lactic acid have a strong antibacterial effect. Besides the antimicrobial effect, the studies reviewed show that the use of lactic acid as a meat sanitizer does not have a significant impact on sensory and/or physic-chemical characteristics.” (Final Report)
In light of these findings, we decided on a lactic acid spray to decontaminate carcasses, to reduce the total bacterial populations on the carcass surface. The level of the reductions will vary by carcass conditions, acid concentration, and temperature. A typical reduction has been found to be as much as 90% (1 log10 cycle) which is what we expect to see. Sufficient lactic acid should be sprayed on the carcass such that some of it drip off.
The effectiveness of these acids will vary depending on the following:
- concentration (dosage),
- the application temperature,
- contact time,
- the amount of time spent spraying a carcass (it seems self-evident, but research clearly shows that the more time is spent on a carcass, the cleaner it will be)
- the water pressure,
- distance of the hose nozzle from the carcass, especially if hot water is used because the closer the nozzle is to the carcass, less heat is lost as the water travels through the air.
- the sensitivity of the native microflora to the specific compound, and
- to a certain extent the design of the specific equipment.
Organic acids are self-limiting due to discoloration of meat which occurs at or above the 3% concentration level.
Wash only one carcass at a time. It is important for the worker to give each carcass the full attention that it needs and will reduce cross contamination.
Distance from the hose nozzle to the carcass during spraying is important.
Use a gentle sweeping motion to apply the lactic acid to the entire carcass surface.
Work methodically from top to bottom to ensure that all carcass surfaces are treated with lactic acid.
Initially, a garden sprayer can be used. This type of sprayer is relatively inexpensive and simple to operate. In general, garden sprayers operate with a gentle flow rate. Use of this sprayer to thoroughly rinse a carcass may require extra time so that an adequate amount of 2% lactic acid is dispensed. Also, many of these garden sprayers are not equipped with a pressure gauge and require manual exertion to pressurize (unless retrofitted as described below).
It is reported that in general, hot water is more effective at removing bacteria than warm or cold water. Hot water may discolor muscle tissue that is exposed on carcass surfaces. Therefore, consider using warm water if hot water is not used to wash carcasses. Washing carcasses with cold water do remove bacteria by virtue of physical force; yet, it does very little to injure or kill bacteria that may remain on carcass surfaces. This step is so counter-intuitive to meat processing staff that intense comparative studies is underway at Meat Only to determine the validity of this point and findings will be reported on.
The water stream is most forceful at the opening of the hose nozzle. The water loses momentum the further it has to travel. As with temperature, it is a good idea to keep the nozzle no more than 30cm from the carcass surface. A Sanitizing Halso system will be developed for the future to replace the garden hose spray. It will be designed to deliver the lactic acid solution at a maximum pressure of 40 psi. FSIS has no current requirements concerning the minimum and maximum pressure for organic acids (i.e., lactic acid, acetic, and citric acid) when they are applied onto livestock carcasses. However, the rescinded FSIS Directive 6340.1—Acceptance and Monitoring of Pre-Evisceration Carcass Spray (PECS) Systems, dated 1/24/92, stated that the spray pressures should be limited to 50 psi.
In general, research has demonstrated that the more time that is spent washing a carcass, the cleaner it will be. Washing the carcass for a longer period of time allows the force of the water to detach more bacteria and debris. It is suggested to start by allowing 60 seconds per carcass and to reduce this as equipment and operator experience improves to around 20 seconds per carcass.
Suggestions for Establishing a Critical Limit for Food Safety Plan
Here are two ways to define a critical limit for this intervention, which may become a critical control point in the HACCP plan of a very small plant.
1. Specify the length of time (i.e., seconds or minutes) that the carcass will be sprayed with 2% lactic acid. Also, note that enough 2% lactic acid should be sprayed onto the carcass surface so that the whole surface is dripping wet and some of it runs off.
2. Specify the volume of 2% lactic acid that will be applied to each carcass. Also, note that enough 2% lactic acid should be sprayed onto the carcass surface so that the whole surface is dripping wet and some of it runs off.
Suggestions for Monitoring a Critical Limit
Here are two feasible methods for monitoring the Critical Limits suggested above.
1. Use a titration kit to measure acidity (% acid) after preparing a solution of 2% lactic acid. Follow the manufacturer’s instructions closely to get a valid measurement. Record the acidity of each batch of 2% lactic acid solution on a record sheet.
2. During preparation of 2% lactic acid, measure and record the amounts (volume or weight) of water and lactic acid that are mixed together. Mixing together the correct amounts of concentrated acid and water will ensure proper preparation of 2% lactic acid.
Sanitizing Halso System to be developed
The results of the work will be reported here.
JAMES S. DICKSON*, MARGARET D. HARDIN and GARY R. ACUFF. Microbial Inactivation Methods, Arganic Acid Rinses. Microbial Inactivation methods
Development of a Carcass Sanitizing Spraying System for Small and Very Small Slaughterhouses. Final Report to FSIS/TPDS By Gabriel Rodriguez, Gary R. Acuff and Alejandro Castillo. Department of Animal Science Texas A&M University College Station, TX 77843-2471 October 2004. Final Report
Antimicrobial Spray Treatments for Red Meat Carcasses Processed in Very Small Meat Establishments. Prepared by: Department of Food Science, The Pennsylvania State University, Department of Animal Science and Food Technology, Texas Tech University
Department of Food Science and Nutrition, Washington State University. 2005 acid_spray_intervention_booklet_from_Penn_State_2005