Functional oligosaccharides which cannot be digested by human enzyme can not exert their interesting effect until they arrive in the intestinal tract. Subsequently, the beneficial bacteria in tract will metabolize these oligosaccharides selectively as the optimized carbohydrate source. Moreover, these oligosaccharides also can inhibit the pathogens adherence to epithelial cells and enhance the mucosal immune response. Recently, in the market there are some oligosaccharides products aiming to protect human a...