Question: I would like to prepare potato patties made from ground potatoes on the Shavuot holiday. Is this permissible?
Answer: In the previous Halacha we have explained that all forbidden works that apply on Shabbat apply to Yom Tov as well besides for works pertaining to food preparation in honor of the holiday, such as cooking, frying, and baking, etc. which the Torah permits.
Works Forbidden on Yom Tov
There are works which, although associated with food preparation, are forbidden on Yom Tov, such as harvesting one’s field or picking fruit from one’s trees or orchard although one intends to use the grain or fruits on Yom Tov itself. It is likewise forbidden to sheave or thresh wheat on Yom Tov; selecting and grinding are likewise forbidden on Yom Tov, as we shall explain.
The Reason Why These Works Are Forbidden
Our Sages disagree whether or not these works are forbidden on Yom Tov by Torah law or merely by rabbinic enactment.
Some say that the reason for the prohibition of harvesting and picking on Yom Tov is because one usually harvests one’s field, grapevine, or orchard all at once and our Sages therefore prohibited these works so that one does not become overburdened on Yom Tov. Thus, according to this opinion, these works are forbidden by means of a rabbinic enactment and not by Torah law.
On the other hand, others maintain that these works are forbidden by Torah law. In the Talmud Yerushalmi, our Sages derive this prohibition from verses in the Torah.
The Opinion of the Talmud Yerushalmi
Based on this Talmud Yerushalmi, we can infer which works are permissible on Yom Tov and which are forbidden, as follows:
The Torah states, “Only that which is performed for everyone, this alone shall be performed by you.” Immediately afterwards, the Torah states, “And you shall guard the Matzot” to teach us that the only works associated with food preparation which are permitted on Yom Tov are those beginning from “guarding and on”. “Guarding” refers to keeping the Matzot from leavening when they are in dough form. Thus, from kneading dough and on, all works associated with food preparation may be performed; however, works taking place before kneading are forbidden on Yom Tov.
Thus, although kneading dough is forbidden on Shabbat, this is indeed permissible on Yom Tov, as are cooking and baking. Nevertheless, harvesting, threshing, squeezing, and selecting which are works performed before kneading are forbidden to be performed on Yom Tov just as they are forbidden on Shabbat.
Using a Grater
Based on the above, we can understand the law regarding preparing vegetable patties (Latkes) on Yom Tov whereby one must take potatoes and other vegetables and rub them vigorously against a grater after which a batter is formed and then fried, it would seem that this should be forbidden on Yom Tov, for grating vegetables resembles the forbidden work of grinding on Shabbat and this work is forbidden on Yom Tov as well, for grinding is performed before kneading since the wheat must be ground in order to turn it into flour.
Nevertheless, it is indeed permissible to grind vegetables on Yom Tov in order to fry them and the like, for our Sages permitted the use of small, household graters since it is uncommon to grate many vegetables with such a grater; only a small amount is grated based on the amount one needs for the specific Yom Tov. Since the vegetables cannot be grated before the onset of Yom Tov as their flavor turns bad after a day’s time, this is indeed permissible.
Summary: One may grate vegetables using a grater on Yom Tov when doing so is necessary on Yom Tov, such as is the case regarding grating potatoes.