Although rich in high quality protein, soybean contains oligosaccharides, such as raffinose and stachyose, that are not digested by human beings and may cause flatulence . This drawback along with the disagreeable bean flavors has often limited the consumption of soybean as the raw food
material . To overcome these limitations and to develop a probiotic dietary adjunct, we have studied the fermentation of soymilk, the water extract of soybean with the probiotic cultures of lactic acid bacteria and bifidobacteria that have been shown to exert beneficial effects on human hosts . It was observed that soymilk could support the simultaneous growth of Lactobacillus acidophilus
CCRC 14079 or Streptococcus thermophilus CCRC 14085 with Bifidobacterium infantis CCRC 14633 or Bifidobacterium longum B6 . Besides, a significantly higher reduction in the contents of stachyose and raffinose was found in soymilk fermented with mixed cultures of bifidobacteria and
lactic acid bacteria than that fermented with single culture of the respective lactic acid bacteria. These observations further suggested the possibility and the potential of developing the lactic
acid bacteria- and bifidobacteria-containing probiotic soymilk dietary adjunct.
Because a fluid product usually has limited shelf life and occupies large volume, it cannot be readily
transported to distinct markets at low cost. Furthermore, the microorganism is less stable in fluid than
dried product. Therefore, a further attempt was made to dehydrate the fermented soymilk with freeze-drying and spray-drying which are commonly employed in
food industries . Survival of lactic acid bacteria and bifidobacteria during the drying process was investigated. In addition, the viabilities of these probiotic organisms in the dried fermented soymilk after rehydration at different temperatures and under different storage conditions
were compared in the present study.