Food Protection Trends - July 2009 - 431

Of particular importance is operator hygiene during manual punching, where one hand grips the fleece while the fist of the other is used to separate the fleece from the carcass by “punching” down each flank to above the operator’s elbow. It is important that operators have sufficient time and hand-wash facilities to clean their hands and arms between carcasses. Knife incisions through the fleece inevitably lead to microbial contamination. However, such incisions are relatively few and, once made, they can be extended without further contamination by cutting from the inside-out. To prevent cross-contamination by knives and other tools, it is traditional to rinse the knife between carcasses in warm water, then to dip it momentarily in a “sterilizer” unit containing water at a temperature of no less than 82°C. Bell and Hathaway (3) found that rinsing and dipping knives used in sheep dressing reduced the bacterial loading from 5 CFU/cm2 of knife blade to 2.5 log CFU/cm2. Eustace et al. (7) evaluated the effectiveness of knife cleaning at an Australian sheep abattoir by estimating contamination of cleaned knives at each work station. Contamination varied, depending on whether knives were used for “dirty” operations such as fleece incisions or “clean” operations such as trimming. Overall, cleaned knives had an APC around 2 log CFU/cm2 and E. coli was recovered on 18% of occasions, with a mean concentration on positive knives of 0.90 log CFU/cm2. For some markets it is necessary for plants to use a 2-knife system, in which each operator is provided with two knives; at any one time one knife is in use on the carcass and the other is immersed in a sterilizer containing water no cooler than 82°C. The residence time in the sterilizer varies according to the range of tasks done by each operator, from 1–2 s to 30 s. Recently Dykes (6) studied the effect of temperature and time on inactivation of E. coli on knives, finding a 4 log CFU/cm2 reduction in 82°C water for 5 s and a 2 log CFU/cm2 reduction when knives were immersed in water at 60°C for 15 s. Based on the above, a 2-knife system and adequate hand-wash facilities for manual punching were assessed as being superior elements. The scoring is then as follows. • If manual punching is used, do operators have adequate time and facilities to wash hands and arms between bodies? A “yes” scores 0, while a “no” scores 1. • Do you use a 2-knife system? A “yes” scores 0, while a “no” scores 1. • Is the pizzle (penis) heat sealed and clipped? A “yes” scores 0, while a “no” scores 1. The third area assessed was the removal of contamination. While early research studies indicated that steam vacuuming produced significant reductions in microbial loads (see review by Bacon (2)), when on-line steam vacuuming was monitored in a Canadian plant, little reduction in generic E. coli was found (9). The researchers considered that the time for the process in a typical high-speed plant allowed effective treatment of an area only twice that of the steam nozzle. In the present context, steam vacuum was considered effective only if done at more than one work station and when it was concentrated on a small area based on cutting lines. The scoring is then as follows. • Are cutting lines cleaned using steam vacuuming? A “yes” scores 0, while a “no” scores 1. The fifth area assessed was manning levels at key operations. Operations which prevent contamination of the neck with ingesta include rodding of the esophagus (weasand) to push ingesta back into the paunch, sealing the weasand by tying or clipping, and removing its free end. This series of operations is best carried out by more than one operator to ensure that sufficient time is allowed and that they can work with a cleaned implement. Having two operators for key operations effectively halves the line speed, and when two operators are used at any of the following operations a “yes” scores 0, while a “no” scores 1. • Open Y-cut on forequarters • Clear shoulders and foreleg • Remove, clear, rod and clip the weasand • Free the bung (anus) • Open abdomen and strip out of the gastrointestinal tract • Remove pluck (thoracic viscera) The fourth group of questions concerned the contamination from viscera and organs. Preventing contamination from the viscera and head requires several unit operations in sheep dressing. Plugging the bung (anus) prevents leakage of feces. To reduce the risk of perforating the intestine, it is preferable to plug the bung immediately after bleeding and before the carcass is inverted, i.e., while the carcass is suspended only by the hind legs. In 1994, Nesbakken et al. (13) demonstrated the efficacy of bagging and sealing the bung immediately after it has been separated from the tissues and this is considered an important operation. While urine is normally sterile following passage through the kidneys, preventing urine contamination is considered an important aesthetic element in hygienic production. The scoring is then as follows. • Is the bung plugged prior to carcass inversion? A “yes” scores 0, while a “no” scores 1. • Is the bung bagged and tied or is the anal canal tied and removed? Both methods prevent leakage of feces into the channel. A “yes” to either part of the question scores 0, while a “no” scores 1. The sixth area related to line speed. Line speed determines whether operators have sufficient time to properly carry out the required tasks, including cleaning of hands, arms and knives between carcasses. In the tool, slower line speeds score better than higher line speeds; a line speed of less than 8 carcasses per minute scores 0; 8 to less then 10 carcasses per minute scores 1; 10 to less than 12 carcasses per minute scores 2; a lines speed of >12 carcasses per minute scores 3. Lastly, line management was assessed. Adjusting line speed and/or the number of operators at key work stations in response to the cleanliness of different lots throughout the day is an important management tool. A “yes” scores 0, while a “no” scores 1. RESULTS The tool was used to assess operations at six plants and to calculate the Problem and Process Score (Table 1). In general, plants fell into three groups. Plants D and E had low total scores because of managed line speeds, 2-knife cleaning systems, vacuuming of cutting lines at several points and using two operators at many work stations. Three plants JULY 2009 | FOOD PROTECTION TRENDS 431

Food Protection Trends - July 2009

Table of Contents for the Digital Edition of Food Protection Trends - July 2009