Biofilm formation in the milk sampling devices as a result of prolonged use in a dairy processing facility

During prolonged processing of milk, adhesion of bacteria cause biofilm formation in the dairy equipment surfaces. This leads to cross- contamination and shedding of bacteria in processed milk affecting the safety and quality of the milk products. The objective of this study was to determine the extent of biofilm formation in the milk sampling devices used in the dairy industry. To represent a higher incidence of Bacillus licheniformis, raw whole milk (at 4°C) was spiked with vegetative cells of B. licheniformis (4 log cfu/mL) and pasteurized for 12 h, uninterruptedly at 72°C/16 s. Commercial port-septum type of sampling devices was fitted in a pilot-scale pasteurization unit at the points of raw milk-in and pasteurized milk-out. Raw and pasteurized milk samples were drawn aseptically at different intervals of processing to examine the bacterial levels. After 12 h run, attached bacterial cells in the different parts of the sampling ports were swabbed using quick swabs and aerobic plate count was performed using tryptic soy agar with incubation at 32°C for 48 h. Selected isolates from the sampling devices were identified using MALDI-TOF. The experiment was conducted in duplicates and data were compared using ANOVA. The sampling device on the raw side found to experience higher bacterial attachment and biofilm growth (2.12 ± 0.12 log cfu/cm2) compared with pasteurized side (1.14 ± 0.03 log cfu/cm2), indicating a higher attachment potential in the raw side sampling device. A significant difference (P \u3c 0.05) was observed between the biofilm counts in the sampling devices from raw and pasteurized sides. MALDI-TOF revealed B. licheniformis to be the predominant species in the sampling port biofilms on the pasteurized side. However, B. licheniformis, Staphylococcus sp., E. coli, and Strep. uberis were identified in the biofilms of the sampling port on the raw side. The results demonstrated that the prolonged usage may prompt biofilm formation in the sampling devices. This suggests that replacing the septum-based sampling device after a certain interval or processing of milk within a shorter period could help to prevent biofilm formation