Food Protection Trends - October 2008 - 715

TABLE 1. Summary of information from survey of abattoir hot water sterilizing practices – adapted from Midgley and Eustace 2003 (20) Plant Hot water storage (°C) 82 65 90 51 85 60 70 88 none 84 Sterilizer water distribution (°C) 90 93 95 88 90 > 90 90 82 95 80 Type of sterilizer1 Two-knife operation Yes Yes Yes No Yes No Yes Yes No No No. of two- knife locations2 17 11 5 7 24 11 - A B C D E F G H I J 1 Overflow Overflow Overflow Overflow & spray Overflow Overflow & spray Overflow & spray Overflow Overflow Overflow Overflow – immersion baths with continuous water flow; overflow and spray–some immersion baths, some jacketed sprays Two-knife system defined in text below 2 TABLE 2. Total viable counts (TVC) of hands before and after rinsing and of knife blades1 before and after cleaning by rinsing in warm water then immersion in 82°C water on a sheep slaughter floor — adapted from Bell and Hathaway 1996 (3) Treatment Mean log TVC/cm2 (SD) Before treatment 44°C spray rinse (n = 50) Knife blades Knife hands 44°C spray rinse, then 82°C immersion (n = 50) Knife blades 1 After treatment 5.04 (0.41) 5.06 (0.29) 3.29 (0.68) 4.16 (0.42) 5.04 (0.41) 2.42 (0.65) Blades swabbed with cotton gauze swabs; counts at 25°C for 72 h rate of overflow adjusted to ensure the required minimum temperature (82°C) was maintained. Flow rates measured for individual units ranged from 38.5 to 224 liter/h. The extent of lethality of hot water to bacteria is primarily a function of contact time and temperature, and in some plants operators use a two-knife system, in which one knife is held in the sterilizer while the other knife is in use. Where only a single knife is used, the knife is momentarily dipped into the sterilizer between uses. Six of the plants surveyed by Midgley and Eustace (20) had implemented twoknife systems at stations mainly prior to the hide puller; these plants generally had approval to export to the European Union. When two-knife systems were used, the residence time of the knife in the sterilizer depended on chain speed and operator procedures (13). In plants where knives were changed only when operators passed to the next carcass, residence time varied from about 17 seconds in an abattoir killing over 200 cattle per hour to over 60 seconds for those with slower processing speeds. In Australia, the 31 abattoirs that are listed by the EU as eligible to process red meat for export all employ a two-knife system. In New Zealand, nearly 60 establishments are sterilizers and other relevant information was collected. Questionnaires were completed by an additional five plants. A summary of some of these data is presented in Table 1. Typical sterilizer water usage on the slaughter floors was divided between knives, equipment and viscera table as follows: knives (50–55%), equipment (30–35%) and viscera table (10–15%). In 8 of the 10 plants, the temperature of the available hot water had to be boosted for circulation in order to ensure a minimum temperature of 82°C at the knife and equipment sterilizers. Most sterilizers were a water bath type with the OCTOBER 2008 | FOOD PROTECTION TRENDS 715
Food Protection Trends - October 2008

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