A preliminary study on the presence of biofilms on food contact surfaces in selected Sri Lankan fish & shrimp processing factories: setbacks in cu




Biofilms are a matrix of microorganisms which are adhered to and colonized a surface. When formed, they are very difficult to remove and act as a source of contamination in fish and shrimp processing environments. This study was undertaken to investigate the presence of biofilms, their bacterial composition on food contact surfaces in selected fish and shrimp processing factories as there are no records available on this aspect in Sri Lanka. Swabs were taken from selected food contact surfaces in two fish processing factories and two shrimp processing factories 6-8 h after the day's major cleaning operation. Biofilm formation was quantified by Aerobic Plate Count (APC) and Escherichia coli counts. Bacteria present on the biofilms were also identified to their generic or species level. Surface adhered bacteria in surveyed fish processing plants had different levels of APCs [in Colony forming units (CFU)]: on deheading and lolling tables 103 cfu/cm2; filleting boards 103 cfu/cm2; trimming boards 104 cfu/cm2 ; knives 106 cfu/knife; gloves 105 cfu/glove; storage boxes (plastic) 105 cfu/cm2; small cutting boards 106 cfu/cm2; water buckets 106 cfu/bucket. E. coli were found only on some of the food contact surfaces viz. knives (5.0 cfu/knife); storage boxes and filleting boards (<1cfu/cm2). Food contact surfaces in the shrimp processing plants had biofilm formation with high levels of APCs and different levels of E. coli: on grading table, APC 8.9x104 cfu/cm2, E. coli < 1 cfu/cm2 ; on processing table, APC 107 cfu/cm2 , E. coli <1 cfu/cm2 , on gloves APC 107 cfu/glove, E. coli 4 cfu/glove; on block pan APC 105 cfu/cm2, E. coli 2 cfu/cm2, on selecting boxes APC 105 cfu/cm2 , and on bowls used for washing shrimps APC 106 cfu/bowl, E. coli 8 cfu/bowl. Predominant bacteria identified in all selected food contact surfaces in the fish processing plants were Bacillus circulans, Bacillus subtilis, other Bacillus sp., Micrococcus sp., Aerococcus sp., Flavobacterium sp., Pseudomonas fluoroscens, and Pseudomonas aeruginosa. Salmonella, E. coli, were found to occur at a lower frequency. In the shrimp processing food contact surfaces, Alcaligenes, Micrococcus, Aeromonas hydrophila, Bacillus subtilis, Bacillus circulans, other Bacillus species, Flavobacterium, Pseudomonas species, Enterobacter aeroginosa, E.coli and Salmonella were also found nevertheless the incidence was low. This study showed that food contact surfaces in fish and shrimp processing industry supply an excellent environment for biofilm formation irrespective of the different cleaning methods used at present. Gloves, small cutting boards used on the top of the tables and knives are of high affinity to contaminate the product with its detached biofilm bacteria.

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