Fuente: WIPO "milk" This method ferments a milk starting material by using a Lactocuccus lactis and a Bifidobacterium that have the property of maintaining at least a 30% survival rate of the Bifidobacterium when a culture medium containing, for example, 1% (W/W) glucose and 10% (W/W) reduced skim milk is inoculated with 5.0×106 to 2.0×108 CFU per 1 ml of culture medium of a Lactococcus lactis that does not have a cell-wall-localized protease and 1.0×107 to 3.0×109 CFU per 1 ml of culture medium of a Bifidobacterium bacteria, the bacteria are cultured, and when the pH of the culture medium has reached 4.6 to 5.5, the culture medium is rapidly cooled from the culturing temperature to 10°C and stored for two weeks at 10°C.