Food Protection Trends - March 2010 - 161

TABLE 1. Cannery cooling surveys: anaerobic spore content1 Samples Anaerobic spores/ml Median Range % Positive < 0.03 NR < 0.1 < 0.03 < 0.03–9.3 < 1.0–4.0 < 0.1–5.9 < 0.03–4.6 15.2 4.0 NR 10 Cooling system Reference 59 210 171 274 SP and R SP and R NR R (7) (11) (19) (29) Adopted from Thompson and Griffith (29) SP, single-pass; R, recycled NR, not reported to 10-12. The former National Food Processors Association (currently the Grocery Manufacturers Association) and the Can Manufacturers Institute (NFPA/CMI) Container Integrity Task Force (17) calculated that between 1940 and 1982, 1.3 × 1012 cans of low-acid foods were consumed. Over the same period there were five botulinal incidents in which container leakage was observed as the source of contamination. Thus, the Task Force estimated the probability of botulism from container leakage as 3.8 × 10-12, or one chance in every 260 billion cans of foods consumed. Several surveys on bacteriological quality of cannery cooling water have been conducted to determine the aerobic plate count (APC) and the incidence of spores from mesophilic anaerobic sporeformers. The conditions that permit a buildup of mesophilic anaerobic sporeformers would be favorable for C. botulinum. The objectives of this paper are: (1) to provide a review of the available literature on bacteriological quality of cooling water used in thermal processing plants, and (2) to make recommendations on adequate testing and control of microbial population build up in retort cooling water to reduce the possibility of post-process contamination. SURVEyS ON BACTERIOLOGICAL QUALITy OF CANNERy COOLING WATER Few reports on the microbiological quality of cooling water used in food canning facilities have been published. The bulk of studies that are available were conducted two or more decades ago. Kibler et al. (12) conducted a survey in nine canneries, located across the United States, for mesophilic anaerobic spores, including C. botulinum. Numbers of positive samples in cannery water out of the total 60 samples cultured for mesophilic anaerobic spores were 7 for cooling canals and 17 for cooling towers. None of the samples contained C. botulinum. Most of the water was treated with chlorine, but sometimes pond water was used for the cooling process. Pond water was pumped into the plant when needed, treated with an iodophor, used in the cooling process and then returned to the pond. The authors concluded that because of the presence of numerous mesophilic anaerobic bacteria in the cooling water, good manufacturing procedures should be followed, good sanitation procedures enforced, container defects minimized and post-processing equipment regularly cleaned and sanitized. Lake et al. (13) conducted another survey in three low-acid food canneries (Cannery A, Cannery B and Cannery C) on enumeration and isolation of mesophilic anaerobic sporeformers from cannery post-processing equipments and cooling water. The authors reported that a significant number of these spores were isolated from various pieces of equipment. In one instance a depalletizer turntable (in Cannery C) had a population of 3.5 × 103 CFU/ in2. Spores were also isolated from the can cooling water in two of the canneries (Cannery B and Cannery C). The highest number of anaerobic spores was found in Cannery C (20 CFU/in2). The isolates from cooling water were identified as C. sporogenes, C. pasteurianum, C. beijerinkii (Cannery B) and C. acetobutylicum (Cannery C). The retorting methods used in these two canneries were continuous rotary cookers (Cannery B) and hydrostatic cookers (Cannery C). Anaerobic spores were not detected in cooling water in the cannery that used still cookers (Cannery A). The low total aerobic plate counts found in the still retort system and high counts in hydrostatic type cookers were consistent with the cooling water counts reported by Graves et al. (7) and Odlaug and Pflug (18). No correlation was noted between mesophilic anaerobic spore counts and total aerobic counts. C. botulinum was not isolated from any of the survey samples. The authors concluded that post-process can handling equipment in these plants was the main source of anaerobic spores. In this particular study, can cooling water appeared to be an additional source, but of lesser significance. Mesophilic anaerobic sporeformers were cultured from recycled cannery cooling water by Thompson and Griffith (29). Chlorinated, recycled water for cooling of containers in still retorts was sampled over a 27-month period at one food processing plant. Of 274 samples taken, 28 contained mesophilic anaerbic spores. The isolates were characterized as Clostridium spp., with C. butyricum and C. barati representing 55% of the isolates. The authors summarized the total anaerobic spore count data and compared them with results of others (Table 1). MARCH 2010 | FOOD PROTECTION TRENDS

Food Protection Trends - March 2010

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