Bifidobacterium longum survival during frozen and refrigerated storage as related to pH during growth

Four strains of Bifidobacterium longum were grown at pH 5.5, 6.0, 6.5 and 7 .0 and evaluated for survival and bile tolerance during frozen and subseque nt refrigerated storage in milk. There were no reductions in cell numbers f ollowing initial freezing,There were effects for strain, pH and storage for th ree of the four strains of B. longum during storage at 5 degrees C in m ilk. Bifidobacterium longum S9 was more stable than other strains in that n o losses occurred, regardless of pH during growth. Results were variable fo r strains II, III, and ATCC 15707 grown at the various pH levels. Bifidobac terium longum S9 did not lose bile resistance during refrigerated storage a s the other three strains did.