HELP!! my steamed rice cake is chewy and gummy?

yesterday i made steamed rice cakes (puto) and i followed all the instructions, but i thought the bread will come out fluffy and spongly. instead, it came out chewy and bitter. have i done something wrong with the steamer? i steamed it in medium temperature in the stovetop for 30 mins. also, i used korean rice flour, not sweet rice flour.