Here is an explanation, for those unfamiliar with what Kitniyot is..
http://www.kashrut.com/Passover/Kitniyot/What is Kitniyot?Authored by the Orthodox Union. Copyright © 2008 Orthodox UnionReprinted with permission of the Orthodox Union. Origional article is here
In addition to the Torah’s restrictions on owning, eating and benefiting from chametz, an Ashkenazic minhag developed in the middle ages to not eat certain foods known collectively as “kitnios”. The Mishnah Berurah (453:6 & 464:5) cites three reasons for the minhag (a) kitnios is harvested and processed in the same manner as chametz, (b) it is ground into flour and baked just like chametz [so people may mistakenly believe that if they can eat kitnios, they can also eat chametz], (c) it may have chametz grains mixed into it [so people who eat kitnios may inadvertently be eating chametz]. Although initially there were those who objected to the minhag, it has become an accepted part of Pesach in all Ashkenazic communities.
Which foods are kitnios
The earlier Poskim mention that rice, buckwheat/kasha, millet, beans, lentils, peas, sesame seeds and mustard are included in the minhag (see Beis Yosef O.C. 453, Rema 453:1 & 464:1 and Mishnah Berurah 453:4, 7 & 11) and it is generally accepted that corn (see below), green beans, snow peas, sugar-snap peas, chickpeas, soybeans, sunflower and poppy seeds are also forbidden. On the other hand, potatoes (see below), coffee, tea, garlic, nuts, radishes and olives and not treated as kitnios (see Sha’arei Teshuvah 453:1, Chayei Adam 127:7 and others). Iggeros Moshe (O.C. III:63) assumes that peanuts are not kitnios but notes that some have a custom to be machmir. Some other examples of foods which are or aren’t kitnios will be noted below and in the “Derivatives of kitnios” section.
Iggeros Moshe explains that the minhag to not eat kitnios developed differently than other minhagim and therefore rules that only foods which we know were specifically included in the minhag are forbidden. [See also Chok Yaakov 453:9 who makes a similar point]. With this he explains the generally accepted custom to not consider potatoes to be kitnios even though logically they should be, as follows: the minhag of kitnios can be dated back at least until Maharil, who died in 1427, and potatoes didn’t come to Europe until the 16th century, so potatoes were a “new” vegetable which wasn’t included in the minhag. This logic has also been suggested as a basis for permitting the consumption on Pesach of a grain called quinoa. The thinking is that since quinoa, which has only recently been introduced to the Northern Hemisphere from its native South America, was never considered kitnios, it remains permitted on Pesach even though logically it should be included in the minhag. While this logic is sound, it is noteworthy that quinoa is often packaged in plants that also package wheat and barley, and it is possible that those grains (i.e. chametz) could get mixed into the quinoa. Therefore, before using quinoa on Pesach, someone who knows how to distinguish between these grains should check the quinoa to ascertain that it doesn’t contain any wheat or barley. An important “exception” to the aforementioned rule that “new” vegetables aren’t included in the minhag, is corn/maize which Mishnah Berurah 453:4 and others rule is kitnios even though it was introduced to Europe after the minhag had already begun.
As a rule, spices are not considered to be kitnios and Rema 453:1 makes a point of noting that anise/dill and coriander are not kitnios. Taz 462:3 notes that all spices should be checked before Pesach to establish that no chametz-grains are mixed in, and elsewhere Taz (453:1) specifically notes that anise and coriander seeds should be thoroughly checked. In addition, Taz and Magen Avraham (453:3) discuss whether fennel, cumin and caraway seeds (i.e. three variations of “Kimmel” ) can possibly be checked (and used) for Pesach. Thus, as a rule, spices are not kitnios but require special care to guarantee that no chametz-grains are mixed into them. Some hashgochos consider fenugreek to be kitnios while others do not, and the surprising ramifications of this question will be noted towards the end of the article.
Derivatives of kitnios
The earlier Poskim, including Rema, clearly indicate that oil made from kitnios is forbidden on Pesach, but some of the later Poskim suggest that such oil may be permitted because some of the original reasons for the minhag don’t apply to the oil extracted from kitnios. It is generally accepted to follow the stricter opinion in this matter, but the lenient opinion is sometimes considered as one factor in a larger decision.
Therefore, on Pesach one may not use corn or soybean oil (a.k.a. “vegetable oil” ), and some do not use peanut oil either (see above regarding peanuts). Oil from olives, palm, coconut and walnuts are acceptable for Pesach use because the fruits they are extracted from is not kitnios. Minchas Yitzchok (III:138:2) suggests that cottonseed oil is kitnios, but in a subsequent teshuvah (IV:114:3) he reconsiders this position (see also Mikra’ai Kodesh, Pesach II:60:2); in the United States cottonseed oil is generally not considered to be kitnios but in Eretz Yisroel there are those who refrain from using it.
Canola oil was first approved for food use in the United States in 1985 and there are those who therefore suggested that it is a “new” item which shouldn’t be included in the minhag, as per Iggeros Moshe cited above. However, the fault with this line of reasoning is that “Canola oil” is actually “Rapeseed oil” (a.k.a. colza oil) which has been used for centuries in Europe. [“Canola oil” is rapeseed oil specially bred to have less erucic acid (a suspected cause of heart disease) and therefore only this better variation of rapeseed oil is approved for food use in the USA]. In fact, Avnei Nezer (373 & 533) and Maharsham (I:183) specifically mention rapeseed and its oil in their discussions of kitnios. It is also noteworthy that canola often grows near oats, and therefore even those who might argue that canola isn’t kitnios would agree that all of the oats must be removed before the oil is extracted from the canola.
In recent decades, scientists have learnt to manipulate microorganisms to create and convert all types of enzymes and foods. This has had dramatic effects on the world of kashrus, including kitnios. What happens if one takes bland-tasting corn, and uses enzymes to liquefy and sweeten it – does the resulting corn syrup remain forbidden as kitnios? Is the halacha possibly more lenient if one takes the aforementioned corn syrup and uses enzymes to convert it to sour-tasting ascorbic acid?
These questions depend on a machlokes Rishonim cited in Mishnah Berurah 216:7 regarding the kashrus of musk – a fragrant byproduct of blood which is found in the abdominal gland of the male musk deer. Some Rishonim hold that since blood is non-kosher, musk is also forbidden, but others holds that once the blood is nishtaneh – changed – it loses its original identity and becomes an innocuous kosher liquid. Mishnah Berurah rules that as relates to issurim d’rabannan one may be lenient.
Accordingly, some hashgochos hold that since kitnios is merely a minhag (i.e. even less than an issur d’rabannan) one can be lenient and certify kitnios which was truly nishtaneh. In order to qualify as “nishtaneh” the kitnios must go through a significant change in taste; therefore in the cases noted above, they would certify the ascorbic acid due to the dramatic change in taste from sweet to sour but wouldn’t permit the corn syrup since it isn’t changed/nishtaneh “enough” from the corn which it came from. This rationale is the basis for some hashgachos’ certification and/or acceptance of certain productions of MSG, aspartame and xanthan gum for Pesach. Some argue that Mishnah Berurah’s ruling is limited to cases of b’dieved and doesn’t justify the l’chatchilah creation/certification of such an item, and others argue that nishtaneh may be limited to cases where the forbidden item becomes inedible in the middle of its conversion to the “new” item. We will see below that even those who take the strict position in this matter generally agree that foods created with these ingredients are b’dieved permitted on Pesach.
Halachos of kitnios
The minhag to not eat kitnios begins on Erev Pesach at the same time that one may not eat chametz (Shevet HaLevi III:31 citing Chok Yaakov 471:2 and others). Although one may not eat kitnios, one may own and derive benefit from kitnios. Therefore, on Pesach one may keep cans of sweet corn in their property or feed millet to their parrot. Additionally, children, people who are ill, and people whose diet is otherwise restricted and must eat kitnios, are excluded from the minhag and may do so after consulting with a Rav. This halacha is quite relevant to baby formulas and nutritional supplements (e.g. Ensure) which invariably contain kitnios, and are usually used by people who have few non-kitnios choices, if any. When such foods are used on Pesach they should be prepared in special non-Pesach and non-chametz utensils, which should not be washed with the Pesach dishes. [It must be noted that although the halacha is quite lenient in permitting children and the infirm to consume kitnios, the halacha is quite strict regarding the consumption of chametz, and one must therefore be sure that the product is truly chametz-free before consuming it. The subject of determining whether an item is merely kitnios or if it possibly contains chametz is beyond the scope of this article and will IY”H be dealt with separately].
Kitnios is batel b’rov, which means that if someone accidentally put kitnios into their Pesach food, the food is b’dieved permitted assuming the food contains more non-kitnios than kitnios (Rema 453:1 as per Mishnah Berurah 453:9). This means that although the food may have a pronounced taste of kitnios, the food is permitted (unless there are recognizable pieces of kitnios which haven’t been removed). Therefore, if a beverage is sweetened with aspartame made of kitnios shenishtaneh, even those people who hold that aspartame is forbidden (as explained above) may drink the beverage because the aspartame is batel b’rov in the other ingredients. Similarly, we have seen that there is a disagreement as to whether fenugreek is kitnios. Nonetheless, even those who follow the strict approach may consume maple syrup which is flavored with fenugreek (as it often is) because it is batel b’rov. Thus, although we’ve seen a number of disagreements as to whether certain foods are or aren’t kitnios, those disagreements are limited to one who wants to consume the actual item (or a hashgachah certifying someone else who is intentionally putting the ingredient into a food), but these disagreements rarely affect consumers.
Other Minhagim
In addition to the well-known minhag of not eating kitnios, the Rema (467:8) cites customs to not eat honey, raisins, dried fruit, sugar, saffron and cloves, and other Poskim cite numerous other customs from specific communities. Many of these minhagim are limited to cases where the person doesn’t know for sure that the product doesn’t contain chametz, and therefore many of these minhagim are not practiced nowadays because the hashgachah on the food guarantees that it is chametz-free. As with all matters of halacha, one who is unsure as to whether a family or community custom remains in effect, should consult with their Rav.
