Dynamics of microflora on conveyor belts in a beef fabrication facility during sanitation

The sanitation process commonly used for meat processing facilities includes three major steps: removal of soil (meat debris), cleaning and degreasing with detergent, and sanitization. The microbiological effect of such sanitation practice in commercial setting is largely unknown. Samples were collected from food-contact surface (CS) and non-food-contact surface (NCS) of two conveyor belts (Belt 1 and Belt 2, the latter of which was actively dried with air movers after sanitization) in a commercial beef fabrication facility at five time points: before cleaning (BC), after soil removal (ASR), after cleaning with detergent (ACD), 1.5 h after sanitization (AS), and before work the next day (BW), for enumeration of aerobes, lactic acid bacteria (LAB) and Enterobacteriaceae (EB). Selected isolates from each group of organisms from NCS of Belt 2 were also identified by 16 S rRNA gene sequencing. The mean numbers of aerobes, LAB and EB recovered BC were mostly about 6.0, 3.0 and 2.0 log CFU 1000 cm−2, respectively. None of the individual steps alone resulted in significant changes in numbers of the three groups of microorganisms, with the exception of ACD of both surfaces of Belt 1 and AS of NCS of Belt 2 where ≥1.5 log reduction was observed for aerobes and LAB, respectively. However, the overall sanitation process resulted in significant reductions (p < 0.05) of all three groups by up to 3 log units. Air drying of Belt 2 did not result in further reduction in numbers of any of the three groups of bacteria. A total of 567 bacterial isolates were identified to the genus level. The aerobes from BC, ASR, ACD, AS and BW included 75, 89, 90, 69 and 81% of Gram-negative bacteria, with Pseudomonas (27%), Pseudomonas (34%), Brevundimonas (24%), Stenotrophomonas (19%), and Stenotrophomonas (24%) being the most prevalent genus, respectively. Five and 8 genera of LAB and EB were identified BC, with Carnobacterium (48%) and Yersinia (42%) being the most prevalent genus, respectively. Carnobacterium spp. were present at all five time points, mostly as a dominating component. Unlike EB whose diversity remained largely unchanged from BC to AS, the diversity of LAB decreased to only 1 genus.