COMPARISON OF METHODS FOR DETERMINING COLIFORM AND ESCHERICHIA-COLI LEVELS IN APPLE CIDER

The main objective of this research was to determine the easiest and m ost reliable media for enumerating coliform bacteria and Escherichia c oli levels in apple cider During the autumn of 1994 a total of 59 appl e cider samples were collected directly from 12 cider producers and we re assessed for bacterial levels and pH. Plate count agar was used to determine heterotrophic bacteria levels, Coliform levels were determin ed using three different media: violet red bile agar (VRBA), Petrifilm High Sensitivity Coliform Count Plates (PHSCCP), and Trypticase soy a gar with a VRBA overlay (TSA/VRBA) for attempted recovery of coliforms injured by the low pH of the apple cider. Eosin methylene blue agar ( EMBA) and Petrifilm E. coli Count Plates were used to screen cider sam ples for E. coli. Apple cider had an average pH of 3.34 +/- 0.08. Hete rotrophic bacterial levels ranged from 2.30 to 7.11 log CFU/ml. All ci der samples contained coliform bacteria with levels varying greatly; o n the different media, we found the following: on VRBA, <1.00 to 4.37 log CFU/ml; on TSA/VRBA, 1.20 to 4.40 log CFU/ml; and on PHSCCP, <1.00 to 4.56 log CFU/ml. Coliform levels were most easily determined in ap ple cider by using PHSCCP. However TSA/VRBA proved to be more reliable ; coliform detection was significantly (P < 0.05) increased. EMBA was ineffective for screening apple cider for E. coli, with the law pH of the cider producing many false-positive results. E. coli was only reco vered by using Petrifilm E. call Count Plates with one of the 59 sampl es positive for E. coli (non-O157:H7) at a level of 10 CFU/ml.