Surface Contamination In Fish Processing Plants - Brief Article

Nutrition Research Newsletter, August, 2001 by Hanna Miettinen, Kaarina Aarnisalo, Satu Salo, Anna-Maija Sjoberg

The hygiene of the processing environment is a significant factor in the production of microbiologically safe and good-quality products in the fish industry. Both quantity and the specific type of microbial flora are important factors for evaluating the hygiene of the processing plant. Hygienic production is even more essential for product that are eaten uncooked, such as cold-smoked and cold-salted fish and roe. Microbial growth may reach high levels in fish products if they are stored incorrectly. Also, vacuum packaging, cold storage, and high-salt concentrations may favor growth of pathogenic Listeria monocytogenes compared to other competing microbial flora.

Since there are very few publications concerning hygiene in the fish industry, four Finnish researchers studied the level of surface hygiene in fish processing factories with different hygiene-monitoring methods. Miettinen et al also determined the level and presence of Listeria in the factory environment and products. Samples were taken from 28 factories from 1996 through 1998. Surface samples were taken after cleaning and just before processing begins, while surfaces in direct contact with products (knives, cutting boards) or indirect contact (door handles) were also sampled. Both ATP measurements and contact agar methods were used to detect pathogens.

Based on levels of total aerobic heterotrophic bacteria, approximately half (52.2%) of the cleaned surfaces were clean or only slightly contaminated ([is less than] 1.8 CFU/[cm.sup.2]), 21.8% moderately contaminated (1.8-5 CFU/[cm.sup.2]) and 26% unacceptable ([is greater than] 5 CFU/ [cm.sup.2]). Most of the unacceptable samples had counts [is greater than] 20 CFU/ [cm.sup.2]. Results of the ATP and the total bacteria contact agar slide methods were poorly correlated. However, 68% of the samples were categorized as good to moderate or unacceptable with both methods. Chopping boards in particular were heavily contaminated with enterobactereia, while most of the molds were found on packaging tables and scales. Listeria spp. were found in 65% of the factories. Cold-smoked fish was the most contaminated, with 75% Listeria spp. and cold-salted fish with 20% L. monocytogenes. Listeria innocua was found in the samples more than twice as often as L. monoctyogenes.

The results show that the number of well or adequately washed and disinfected fish factories was small (2 of 28). The importance of good manufacturing practice and hygiene in the fish processing industry cannot be underestimated, especially considering the amount of pathogens such as L. monocytogenes found in this study. After the evaluation of the hygiene results found in this study, it was possible for the factories to focus cleaning and disinfection on the most important surfaces and machines. It is essential to evaluate the hygiene of these factories on a regular basis with effective and appropriate hygiene-monitoring methods.

Hanna Miettinen, Kaarina Aarnisalo, Satu Salo and Anna-Maija Sjoberg. Evaluation of Surface Contamination and the Presence of Listeria monocytogenes in Fish Processing Factories, Journal of Food Protection 64(5): 635-639 (May 2001) [Correspondence to: Hanna Miettinen, Phone: 358-9-456-5150. Fax: 358-9-455-2103. E-mail: hanna.miettinen@vtt.fi]