A STAINING PROCEDURE FOR VIABILITY ASSESSMENT OF STARTER CULTURE CELLS

In this paper a staining procedure for detection of viable starter cul ture cells (Lactobacillus, Pediococcus) is described. The method is ba sed on fluorescence in microscopy and staining with two fluorochromes, Erythrosine B (ERB) and 4',6-diamidino-2-phenylindole (DAPI). The sta ining procedure revealed viable cells by bright blue or bright green f luorescence, whereas dead or heat-treated cells had only low intensity fluorescence. Counting of viable cells of lactic acid bacteria dried on microscope slides was carried out both manually and by an image ana lyser, and was compared with the results from the conventional plating method and from adenosine 5-triphosphate (ATP) determinations. The ba cterial cells were dried on microscope slides before staining to give an indication of whether the staining procedure may be useful for defe ction of viable and dead cells in cryosections. The staining pattern o bserved with Lactobacillus and Pediococcus cells was not confirmed wit h Micrococcus cells.