Turbidimetry as a rapid method for enumeration of microorganisms in raw vegetables

25 samples of different vegetables from the raw material stock of a salad p roducing company were checked for total cell counts and for counts of Enter obacteriaceae and pseudomonads before and after washing in cold water. Init ial cell counts of the unwashed samples have been found to be between 4 x 1 0(4) and 2 x 10(8) cfu/g. They were reduced by washing once in cold water b y 0.5 to 1.5 log steps. In more than 25 % of the samples cell counts were n ot reduced by washing. Enterobacteriaceae and pseudomonads constituted the major group of total cell counts (together up to 95 %). Total cell counts o f 10(6) cfu/g and more in 15 out of 25 unwashed samples and in seven washed samples demonstrate that raw vegetables may contain high numbers of microb ial contaminants and therefore may constitute a hygienic risk as ingredient s of MPF products. In 12 out of the 25 samples; cell counts were detected indirectly by measur ing the optical density with an automated turbidimeter (BIOSCREEN). Detecti on times below 24 hours and high correlation between direct plate counts an d turbidimetric data (R > 0.900 for single sorts of vegetable and R > 0.820 for the total estimation) confirmed once more the suitability of turbidime try for microbial enumeration. Modified VRBD broth without Neutral Red yielded better results regarding de tection of Enterobacteriaceae and pseudomonads than Mossel broth.