Sometimes seeds make the eggplant bitter. I don't know how to tell the difference between male and female in the Japanese or Chinese versions but Alton Brown did a whole show on eggplant and he surmised that one of the sexes produced a bitter result. Therefore it was best to choose "x" sex of eggplant at the store or market. I regretfully cannot remember which sex he said was best
so...wish I could help!