Reconstituted skim milk (RSM, 10% w/v) was supplemented with one of five polysaccharides (dextran, inulin, polydextrose, raffinose and trehalose, each at 5% w/v) and mixed with the cell concentrate of exponential or stationary phase cultures of Lactobacillus paracasei NFBC338 before freeze drying. Following freeze drying of the stationary phase cultures, the highest viability was obtained in RSM alone (1.29 x 10(10) CFU/g), while during powder storage a beneficial effect on culture viability was obtained in powders containing dextran, where an 11-fold improved survival at 37 degrees C compared with RSM was attained. The viability of freeze dried exponentially growing cells was improved 4-fold when dried in media containing inulin compared to RSM alone, while stability during storage was improved up to 100-fold by the polysaccharides in the order inulin > polydextrose > RSM. The presence of dextran led to some protection of viability of Lb. paracasei NFBC338 under acidic conditions (pH 2.5), where the rate of viability decline (D value) of the dried culture was 26 min compared with 19 min in RSM in a simulated gastric environment. The usefulness of the prebiotic gum acacia for improving bifidobacterial survival during spray drying and powder storage is also reported, with a view to developing novel synbiotic ingredients.