In the Maftir for Parshat HaChodesh, we read about the first Pesach that was to be celebrated in Egypt and the subsequent holiday to remember the Exodus that would be celebrated annually. There is an explicit commandment not to eat Chametz, yet we see no Biblical prohibition not to eat kitniyot.
What are kitniyot?
The Shulchan Aruch describes kitniyot as products that can be cooked or baked in a fashion similar to the five chametz grains (wheat, barley, spelt, oats and rye) yet are not chametz.
Where did the tradition for Ashkenazim not to eat kitniyot come from?
The Sefer Mitzvot Katan by Rabbi Yitzchak of Courville (France 1210-1280) mentions that some communities do not eat kitniyot on Pesach. This minhag was observed as well in the community of the Maharil (Rhineland, Germany, 1365-1427). The custom eventually spread to all Ashkenasic communities.
The earlier poskim (Beit Yosef, Rema, Mishna Brura) consider the following to be kitniyot: rice, buckwheat/kasha, millet, beans, lentils, sesame seeds, peas and mustard (even though mustard is not officially kitniyot it just grows like kitniyot).
Over time, more “kitniyot” have been added to the list. There is now a list which includes over 55 legumes that are considered to be kitniyot!
Rav Moshe Feinstein argues that only foods that were specifically included in the original minhag are forbidden. Therefore, potatoes are not a problem as they were only introduced in Europe in the 16th century (imagine if we couldn’t have potatoes on Pesach!). Peanuts were also not around at the time of the chumra and were eaten on Pesach in Lithuania and in the United States (yet many Ashkenasim have taken the stricter view and don’t eat them). Quinoa, a relatively new discovery certainly was not part of the chumra and should not be considered kitniyot (yet it is still labeled as kitniyot in Israel).
Corn, which was certainly unknown in Europe at the time of the chumra somehow became added to the list.
Rav Dov Lior does not consider soy to be kitniyot as it only reached Europe 100 years ago. He also says that string beans and fava beans in their pods are not kitniyot as in that state they are considered vegetables.
There are also leniencies for kitniyot derivatives. Maharsham (1835-1911) permitted oils of kitniyot as did Rav Kook. Rav Melamed points out that soybean, cottonseed and canola (rapeseed) oils are not included in the prohibition and we may be lenient (yet they will still be marked as kitniyot due to the fact that they have a stricter hashgacha). Chocolate that contains lecithin (rapeseed) is also not a problem yet it is still be marked kitniyot or it will say “liftit.”
What we learn from here is that when shopping for Pesach, if a product is labeled Kosher for Pesach-contains kitniyot, those who don’t eat kitniyot must read the ingredients on the label to see if the product is in fact kitniyot or if it is being certified in a stricter manner than the psak from the rabbis that they follow.
If there is a product with a derivative of soy or corn, that does not make the entire product kitnoyot. Even if you say that the corn or soy derivatives are kitniyot they would be batel berov (the small amount of kitniyot would be canceled out due to the fact that most of the food is non-kitniyot).
In Israel there are more options to have access to foods that some rabbis consider kitniyot while others do not as there is a large Sephardic population. All of these products must have a Kosher for Pesach Hashgacha to ensure that no other grains were mixed in.
What surprises me is that the US Hashgachot which are very strict in most areas and will not certify most of the products above (except for the potatoes) are lenient in certifying MSG, aspartame and xanthan gum which are a derivative of kitniyot which has changed form.
What we see from here is that we can keep the minhag of not eating the original kitniyot without adding more and more stringencies every year. The key is to be able to stand in the supermarket and read the Hebrew label on almost every product that you are buying.