Bitul orbatel (nullification orof no significance) is a concept inkashrut that stipulates that food is still considered kosher if a small amount of forbidden food is mixed with a permitted food, such as a drop of milk in a meat dish.Bitul b'shishim (Hebrew: בטל בשישים) is the concept that a dish is kosher if the prohibited food is less than one-sixtieth of the entire dish.Bitul barov is the concept that a dish is kosher if less than one-half of the meal contains prohibited food.[1][2]
Orthodox Union Kosher does not allow for bitul containing non-kosher foods.[3] Products containing more than one-sixtieth fish, for exampleWorcestershire sauces containinganchovies or marshmallows containingfish gelatin, are certified by theOrthodox Union as "OU Fish". However, products containing less than one-sixtieth fish are not required to be labelled with the OU Fishhechsher as long as the fish ingredient is listed on the package. Dairy products containing fish that is not batel b'shishim are listed as OU Dairy Fish, to accommodateSephardi Jews who do not mix fish and dairy.[4]
Cheese made with rennet from ananimal who has not beenritually slaughtered is not kosher, due to the presence of non-kosher meat. Many hard cheeses contain less than one-sixtieth animal rennet, but non-kosher animal rennet is not bitul because the rennet is considereddovor ha-ma’amid (a material that gives a product its form).[5]