Inactivation of E. coli and L. innocua in milk by a thin film UV-C reactor modified with flow guiding elements (FGE)

In this study the suitability of a thin-film reactor (TFR) equipped with special flow guiding elements (FGE) was examined to analyse its capability to inactivate microorganisms in milk. Experiments were carried out with UHT-milk inoculated with Escherichia coli (E. coli), DH5α and Listeria innocua (L. innocua) WS 2258. Furthermore, the inactivation of microorganisms originally occurring in raw milk was investigated. E. coli, DH5α and L. innocua serving as biodosimeter were reduced by 4.58-log and 3.19-log, respectively. In milk, the original microorganisms showed a 4-log reduction. Without FGE the reduction was below 0.13-log. Thus, it can be derived that the efficacy of a UV-C thin-film reactor processing absorptive media like milk can be highly improved using FGE. •A 4.73-log and 3.19-log reductions were achieved in E.coli and L. innocua by UV-C treatment ,respectively.•The different fat content has no significant effect on inactivation of E.coli, DH5α in UHT milk using TFR+FGE.•Up to 4 log-reduction was achieved in natural microflora of raw milk.•Higher flow rates like 100 L/h are significantly more efficient than lower flow rates like 30 L/h.