When non-kosher food is accidentally mixed with kosher food, the non-kosher item can be, under certain conditions, considered nullified (batul) and the finished product still kosher. This largely depends on the ratio of the permitted substance to the prohibited substance.

In most cases, the prohibited substance has to be 1/60 or less. Meaning, if 1 gallon of non-kosher food falls into at least 60 gallons of kosher food, the finished product is still kosher and okay to eat. There are some exceptions to this rule. Some prohibited foods only require a simple majority to be nullified, some require a higher level of nullification such as 1/100 (terumah) or 1/200 (orlah) and some can’t ever be nullified.

All of this will be explained below.
1. If a solid non-kosher food is mixed with similar kosher food it will be nullified in a majority as long as they were not cooked together (example: 1 slice of non-kosher raw fish that was mixed with 2 slices of kosher raw fish and there is no way to identify the non-kosher fish). Nevertheless, one person may not cook or eat the entire quantity of the mixed food. The same rule would apply if a pot of non-kosher food was placed near two pots of identical kosher foods and the non-kosher pot remains separated but cannot be identified.

2. If the non-kosher item has a foul taste or adds a bad flavor to the dish, it is considered nullified in a simple majority because one is not enjoying the issur.

1. 1/100 is necessary to nullify terumah (priestly gift from Israeli produce) and Challah (the dough separated as a priestly gift). Both are holy and cannot be consumed by a non-priest or tamei.

2. 1/200 is necessary to nullify klei hakerem (a prohibited crossbreeding of grapes with other plants) and orlah (fruit from a tree within its first 3 years) in Israel.1

1. Chometz that is mixed into a Kosher for Passover item during Passover cannot be nullified.

2. Foods that have a certain significance and are prohibited by themselves (and not an absorption of an issur) as defined below.
a. Beria – A whole creature, such as a bug, or the complete limb (removed from a live animal) cannot be nullified. If it was crushed (pulverized) without the intention to make it batul, i.e. for the purpose of a smoothie, it is permitted.2
b. Chaticha Haroya Lihischabed – A food that is respectable to serve, such as a piece of steak or a nice piece of fish cannot be nullified. If one nice piece of non-kosher meat is added to a cholent with other similar pieces of kosher meat and there is 1/60 ratio of non-kosher meat to kosher meat, the pot is still considered kosher and potatoes and beans are allowed to be consumed, but none of the meat may be consumed.
c. Davar Shebiminyan – Something that is sold by the amount rather than weight, such as eggs which are sold by the dozen cannot be nullified.
d. Something that is intended to add flavor, such as a spice, cannot be nullified as long that the flavor is noticeable.

3. Davar Hama’amid – something that is used to solidify food, such as rennet in cheese, cannot be nullified.

4. Davar Sheyesh Lo Matirin – An item that isn’t permitted right now but can/will become permitted eventually (without nullification), such as an egg laid on Yom Tov and Tevel (Israeli produce before Teruma and Ma’asros [Priestly gifts and tithes for the Levites and the poor] were separated) cannot be nullified when mixed with the same type of food, because the Chachomim did not want to rely on the leniency of bitul when the item would be permitted at a later time (after Yom Tov) or after an action (hafrashas Teruma and Ma’asros).

1. One cannot purposefully nullify an item by adding more of the kosher product so as to make the non-kosher item 1/60, or change the status of a beria/chaticha hareoya lehischabed, in order to cause bitul. Bitul only applies if there was a non-kosher item added accidently and the ratio was 1/60 or less from the start.

2. In general, if the non-kosher item is recognizable within the mixture, such as a piece of meat falling into a pot of milk, the piece itself must be removed and  cannot be nullified (the flavor that remains can be nullified in a ratio of 1/60).

3. When attempting to calculate whether an item can be nullified or not, it must be calculated by volume and not by weight. A majority of food companies measure their products by pounds and kilos rather than by volume (such as liters and gallons). Therefore, the volume must be appropriately calculated in order to determine if the non-kosher item can be nullified.

The “specific gravity” of each item will represent the density. Products with higher specific gravity are denser. The specific gravity of water is 1. When nullification is calculated, the weight needs to be divided by the specific gravity.

For example, the specific gravity of malt syrup is 1.41. 1 pound of malt syrup needs to be divided by 1.41, which equals a volume of 0.709. 0.709 multiplied by 60 is 42.5. This means you must have 42.5 pounds of water to nullify a single pound of malt syrup.

Another example is animal fat. Its specific gravity is 0.9 which means that 1 pound of animal fat, divided by 0.9 equals 1.11. In order to nullify the fat, 66.66
pounds of water is needed.

Another way to measure the volume is to convert the weight into gallons which is a measurement in volume. One gallon of malt syrup is 11.71 pounds, so 1 pound of malt syrup is 0.085 gallons. 5.1 gallons of water is needed to nullify one gallon of malt syrup. A gallon of water weighs 8.34 pounds, so 42.53 lbs. of water are needed to nullify 1 gallon of malt syrup.

Similarly, a gallon of animal fat weighs 7.5 pounds so 1 pound of animal fat is 0.133 gallons and we need 7.98 gallons of water to nullify 1 pound of animal fat.
7.98 gallons of water weigh 66.55 lbs3.

If one doesn’t know how to calculate the volume it cannot be considered as a safeik because the doubt is caused by a lack of knowledge, not a true case of doubt.

OK Kosher only certifies products that are kosher without relying on nullification. This means that 100% of the ingredients must be approved as kosher in order for the finished product to be OK certified.

1 If there’s safeik orlah (the nature of its orlah status is unknown) in produce that grew outside of Israel, it is permitted. See article about
orlah in this issue for further information.
2 After fruits with infestation concerns have been washed well, one
may crush them without checking for insects because the intention is
not to cause bitul. (See Pitchei Teshuva YD 84, 10)
3 The small discrepancy in the final numbers is due to rounding to the
nearest hundredth for the purpose of this article.