Abstract: Novel alpha-glycosylated soybean glycosides wherein one or more glucosyl residues are bound to the soybean glycoside moiety are prepared. Alpha-glycosylation can be enzymatically achieved by subjecting an aqueous solution containing a soybean glycoside, e.g. soyasaponin or isoflavonoid, and an alpha-glucosyl saccharide to an alpha-glucosyl transferase. Suitable alpha-glucosyl saccharides are liquefied starch, partially hydrolyzed starch and sucrose. Alpha-glucosidase, alpha-amylase, cyclodextrin glucanotransferase, dextransucrase, dextran dextrinase and amylosucrase are usable as the alpha-glucosyl transferase. Since in the alpha-glycosylated soybean glycosides the undesirable bitter, astringent, harsh and lingering choky tastes which are common in intact soybean glycosides are reduced or even eliminated by the alpha-glycosylation, they are suitable for use in food products or orally-usable products wherein taste is an important factor.