SELECTIVE ENUMERATION AND SURVIVAL OF BIFIDOBACTERIA IN FRESH CHEESE

Five species of bifidobacteria (15 strains), two strains of Lactococcu s lactis ssp. lactis, two strains of L. lactis ssp. cremoris, and one strain of L. lactis ssp. lactis var diacetylactis were included in a s tudy to develop a selective medium for enumeration of bifidobacteria f rom fresh cheese. Viable counts of bifidobacteria or lactococci on mod ified Columbia agar base (CAB with 0.05% cysteine-HCl) plus raffinose (0.5%) containing various selective agents were compared with non-sele ctive media. The mCAB plus raffinose with lithium chloride (2 g L-1) a nd sodium propionate (3 g L-1) with pH adjusted to 5.1 was used succes sfully as a selective medium for the enumeration of bifidobacteria fro m fresh cheese. Using this medium, it was determined that bifidobacter ia could survive up to 15 days at a level higher than 10(6) cfu g(-1) in a fresh cheese stored at 4 or 12 degrees C. The decrease in the via ble counts of bifidobacteria was faster during storage at 4 degrees C than at 12 degrees C. (C) 1998 Elsevier Science Ltd. All rights reserv ed.