Formation of biofilms on dairy equipment and the influence of disinfectants on them

Scientific studies show that microbial biofilms formed on the surfaces of dairy equipment negatively affect safety of the finished products and constitute a danger to the human health. This is due to the fact that the biofilms, in addition to the saprophytic microflora, may contain pathogenic micro-organisms as well. The present paper reports results of the studies into composition of the microflora of dairy equipment and finished products, the process of biofilm formation on stainless steel with different surface roughness, with the effect of disinfectants on the planktonic and biofilm forms of bacteria determined.It was established that bacteria of the genera Bacillus, Lactobacillus and the Enterobacteriaceae family are most often isolated from dairy equipment and finished dairy products, with staphylococci, enterococci, streptococci, and pseudomonads isolated in a lesser degree. The isolated bacteria mainly form biofilms of high and medium density. It was found that the Escherichia coli biofilms of lower density form on the surface of stainless steel of brand AISI 321 with a surface roughness of 0.16 µm compared to the surface with a surface roughness of 0.63‒0.955 µm. This process takes place at a temperature of 17 °C, over 6‒24 hours, followed by the formation of a high-density biofilm regardless of the surface roughness. It was established that the disinfectant Argenvit proved to be inefficient for the biofilm and planktonic forms of bacteria. The disinfectants P3-ansep CIP, Eco chlor, Medicarine and Maxidez demonstrated bactericidal effect on the planktonic bacteria; they, however, did not act on the biofilm forms. The most effective disinfectant in terms of action on the bacteria in biofilms proved to be the disinfectant Р3-oxonia active-150 based on hydrogen peroxide and peracetic acid.Thus, the data obtained indicate that in order to efficiently sanitize dairy equipment, it is required to use the disinfectants that affect bacteria in the biofilms. This in turn will ensure production of safe dairy products