EQUIPMENT ▶▶▶
Effectiveness of disinfectants on biofilms
Microbiological contamination through formation of bacterial biofilms in dairy equipment compromises the quality and safety of milk and milk products. We take a deeper look at the effectiveness of disinfectants on biofilms in dairy equipment.
BY MATTHEW WEDZERAI B Bacteria
Pseudomonas aeruginosa Escherichia coli
Enterococcus faecalis Enterococcus fаecium Staphylococcus aureus Bacillus cereus
Streptococcus agalactiae Lactobacillus spp
Source: Kukhtyn et al., (2017) 22 ▶DAIRY GLOBAL | Volume 7, No. 4, 2020
iofilms on the surfaces of dairy equipment threaten not only the quality and safety of dairy products, but also the economic viability of dairy enterprises and sustainability of the entire dairy industry. Bacterial
biofilms occur at all stages of dairy processing, from raw milk collection through to waste treatment. Studies show that bio- films on dairy processing lines are characterised by rapid de- velopment, mostly within 12 hours. Biofilm control currently relies on the effectiveness of clean-in-place systems. A short- age of information on the development and control of biofilms in the dairy industry is pushing research towards establishing effective control strategies. The following sections present re- sults from the work of researchers from Massey University (New Zealand) and National Technical University (Ukraine) who carried out separate studies to shed more light on the
Table 1 – The density of biofilms of bacteria extracted from dairy equipment.
Number of cultures with biofilms (%) 74 82
100 79 87
100 29 57
Biofilms density 1.57 1.62 1.75 1.60 1.74 1.77 1.13 1.21
features of formation of dairy equipment microflora, the ability of micro-organisms to form biofilms on non-corrosive steel surfaces and the effectiveness of disinfectants.
Formation of biofilms The ability to form biofilms allows micro-organisms to survive on most technological equipment. A microbial biofilm is a formation of one or several species or genera of bacteria, fixed to the surface and surrounded by a matrix. Biofilm crea- tion involves four main stages: 1) the adhesion of bacteria to a surface, 2) micro-colony formation or microbial mass growth, feeding from the matrix, 3) maturation through quo- rum sensing (cell-to-cell signalling), and 4) detachment or dispersion of biofilm. Microbial adhesion mainly depends on the bacteria species and the physical and chemical properties of the surface to which it attaches. The formation of extracel- lular polymeric substances (the matrix) occurs during the at- tachment stage of the biofilm to the surface. The matrix pro- vides a medium that facilitates the interaction of the micro-organisms in the biofilm. Studies show that micro-or- ganisms constitute 5–35% of the biofilm volume, while the rest is made up of the extracellular matrix. The last stage of biofilm formation (detachment stage) sees microbial cells and enzymes transferred to new sites, thus propelling contamination and aiding potential spread of infection.
The challenge with biofilms The major problem with cleaning and disinfection of biofilms is their resistance to disinfectant treatment. Studies indicate prevalence of biofilms of different bacteria, both saprophyte and pathogenic bacteria extracted from dairy equipment, des pite cleaning and disinfection with several agents. Thus, the ability of the bacteria to form biofilm on dairy equipment surfaces is an important condition of their survival and cor- res ponding contamination of milk products. This calls for re- search to focus on studying the characterisation of dairy equipment microflora, the ability of different bacteria to form biofilms, the composition of biofilms, the differences of equipment surface and possible effects emanating from the
PHOTO: SHUTTERSTOCK
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