Preparation of the bifidus milk powder.

Malt extract and skim milk were used as the culture medium for bifidobacteria. Bifidobacterium longum E194b (ATCC 15707) selected from among four strains grew well in a nitrogen atmosphere regardless of the initial dissolved oxygen level of the culture medium. The optimum temperature range for growth was 34 to 37 degrees C. The viable cell numbers of Bifidobacterium in freeze-dried powder from neutralized bifidus milk were 20 times those found in powder from nonneutralized milk after storage for 30 d at 35 degrees C. The optimum residual water content in the powder for bacterial stability was about 3.5% or less. Bifidus milk powder prepared under these optimum conditions contained at least one billion viable cells even after storage for 30 d at 35 degrees C. The powder must be sealed with material made of aluminium for storage.