Can matzah be made out of rice?
While there is an opinion in the Gemara that rules that rice can become hametz (=leaven) and similarly, can be baked into matzah, this position is rejected by the Mishnah (see Masechet Pesachim, daf, or page 35). On today’s daf a different, but related question is raised – can matzah be made out of wheat flour that is mixed with rice flour? The Gemara quotes a Mishnah in Masechet Hallah (3:7) that clearly rules that if dough that is made from a mixture of wheat and rice, as long as the mixture tastes like wheat, the matzah can be used to fulfill the mitzvah on Passover.
Rabbenu Tam understands this to be similar to the rule that when the taste from a forbidden food can be sensed in a mixture we consider the entire mixture to be forbidden. The Ra’avad argues that even though the wheat flour in this mixture is significant inasmuch as its taste is present, still there will have to be a sufficient amount of wheat flour – a ka-zayit (=olive’s worth) – in what the person ate if he is to fulfill his mitzvah of eating matzah on Pesach. In contrast, the Ramban accepts the approach of the Talmud Yerushalmi (Hallah 1:1) that explains that the issue at hand is not the taste of the mixture. What happens in this case is that the wheat flour causes the rice flour to ferment and become hametz, something that is not true when wheat flour is mixed with other things. Such a mixture can be baked into matzah, as well.
The rice discussed by the Gemara is Oryza sativa, an annual cereal grain that grows in marshy areas or flooded fields. Rice originated in the Far East, but was already brought to Israel in the Mishnaic period. It is usually used as a cereal, and it is difficult to make bread out of it because it lacks bonding agents that would hold the bread together. Nevertheless, it was often mixed with other grains to be used in bread production. The Sages differed with regard to the halakhic status of rice – its proper blessing, whether it can become hametz and matzah, and so forth.