KashrusHalachos of Common Kashrus Scenarios

One may not eat milk and meat together, and for this reason, it is recommended that one keep separate milchig and fleishig utensils, even for utensils which are only used with cold food. The custom is to mark the milchig utensils, and leave the fleishig ones unmarked[1] רמ"א (פט, ד). ואע"פ שהרמ"א כ' סכין, ע' תורת חטאת (עו, ח) שנהגו כל כלי חלב. ופמ"ג (סק"ז) כ' וסימנך, חריצי החלב. . One may not use a utensil with a piercing action (e.g., fork, knife or blender) with the other type of food, but one may use non-piercing utensils for cold foods of the opposite type, if they are washed well first to remove all residue. For example, one may use an ice-cream scoop to scoop chopped liver.

One should designate a knife which is only used for bread[2] פרי חדש (ס"ס פט) , so that he will not use a dairy knife to cut the bread and subsequently eat it with meat (or vice-versa).

When a pot or other item is used with hot food or liquid, taste is absorbed into the utensil. This taste may be brought into the next food cooked in it, and for this reason, one may not use a pot to cook food of the opposite type[3] צג, א , or foods which one intends to eat with the opposite type of food[4] רמ"א (צה, ב) .

Steam of dairy or meaty foods can also transfer taste[5] צב, ז. ואם הדבר העליון קר, דוקא אם יד סולדת בו, כמבואר שם, ובדרך כלל אין זה שייך אלא בדברי לחים. וע' פת"ש (שם) דלדעת רמב"ם אין זיעה אלא בדבר לח.

אבל אם הדבר העליון חם, הזיעה יכול להפליט טעם אפי' אין היד סולדת בזיעה, ע' . For this reason, when using the same stovetop for dairy and meaty soup, one should not cook soups in pots which reach within 12 inches of the oven hood, as the hood may absorb taste from one type and transfer it to the other.

If one cooked meat in a milchig pot, or milk in a fleishig pot, the food is forbidden, and must be discarded, and not given away to a non-Jew or given to one’s pet[6] צד, ג. וליתן לפני כלב של הפקר, הט"ז (סק"ד) אוסר, אבל ע' פת"ש (סק"ה) שיש מתירים, דדוקא חמץ בפסח אסור ליתנו לכלב של הפקר. . If the pot was aino ben-yomo from the other type of food, however, the food is permitted (although the pot may no longer be used).

A. Aino Ben Yomo and Nat Bar Nat

If one did not use a certain pot or utensil for milk (or meat) within the last 24 hours, the pot has a status of aino-ben-yomo, and does not impart a considerable taste into the food cooked in it[7] רמ"א (צה, ב) . If one does not know if a pot or dish was used to cook within the last 24 hours, the pot is also considered aino ben-yomo[8] קכב,ו דלא כרמב"ם (מאכ"א ג,טז) שמשמע סתם כלי הוא בן יומו, וע' ב"י ס' קכב .

Therefore, if one cooked meatballs in a milchig pot, and the pot was not used to cook milk or a dairy dish within the last 24 hours, the meatballs may be eaten. If one does not know if it was used for dairy in the last 24 hours, the meatballs also may be eaten.

If the only milk which touched the utensil in the last 24 hours was cold or lukewarm (below 113 degrees Fahrenheit[9] בדי השלחן (קה, ל) ) when they came in contact, the absorption in the utensil is aino ben-yomo and cannot cause the next food it touches to become assur[10] כל שאינו בחום שהיד סולדת בו אינו מבשל, ע' שו"ע (קה, ב).

וגם, אפי' אם היה בחום יד סולדת בו . For example, if one ate meatballs with a fork after the meatballs cooled off and were not hot to the touch, and was otherwise not used in the last 24 hours, the fork is aino ben-yomo. If the milk was 113 degrees or warmer, the food may become prohibited, and a Rav should be consulted[11] אם המאכל היה בכלי שני, והוא דבר צלול, ע' רמ"א (קה, ג) שאינו מבליע הטעם. ואם הוא דבר גוש בכלי שני, תלוי במחלקת אם הוא נידון ככלי ראשון כל זמן שהיא חם, ע' ט"ז (צד, יד).  .

The exception to the rule of aino ben yomo is, if the food which is cooked in the aino ben-yomo pot is sharp or spicy, such as onions or hot peppers, the food draws out the absorbed taste in the walls[12] רמ"א (צה, ב) . For example, if one cut an onion with a fleishig knife (rendering it fleishig; see later), it may not be cooked in a milchig pot, and if one already cooked it, a Rav must be consulted.

A ben-yomo fleishig pot may not be used to cook food which one intends to eat it with milk[13] רמ"א צה, א or on milchig utensils[14] בדה"ש (צה, ל) הביא מחלקת וכ' ונראה להחמיר (or vice-versa). If one already cooked food in the pot, he may not mix the food with milk, but he is permitted to eat it on milchig utensils[15] רמ"א צה, א . If the food was accidentally mixed with milk, the food may be eaten[16] רמ"א צה, א .

One is permitted to cook food he intends to eat on pareve dishes immediately after eating dairy. For example, one may use a fleishig ben-yomo pot to cook applesauce to be eaten (on disposable utensils) as dessert after a milchig meal.

An aino ben-yomo milchig pot may not be used to cook food one intends to eat with meat[17] ע' גר"א מקיל בזה, וחכ"א מקיל אם אין לו כלי אחר , but may be used to cook food to be eaten on fleishig utensils[18] דאפי' אם הכלי בן יומו, יש סוברים דמותר בכה"ג, ובפרט שיש לצרף דעת הגר"א להתיר. וע' בדה"ש (צה, ל). . For example, one is permitted to use an aino ben-yomo milchig pot to cook fish which one intends to eat on fleishig utensils.

If one cooked pareve food (containing no sharp ingredients) in an aino ben-yomo, milchig pot, it is permitted to mix the food together with meat[19] רמ"א צה, א . The food also may be reheated in a fleishig pot or eaten on fleishig dishes[20] ק"ו מדין הראשון, דאפי' לאוכלו עם המין השני מותר . For example, if one cooked noodles in an aino ben-yomo fleishig pot, he may subsequently transfer it to a milchig pot and add cheese to it.

If one stirred an aino ben-yomo fleishig pot, containing pareve soup, with a ben-yomo milchig ladle, the pot and ladle are still kosher, and the soup should only be eaten with the type of food of the ben-yomo utensil[21] (in this case, milk). The same applies if the pot was ben-yomo and the ladle was aino ben-yomo.

B. Knives and Sharp Foods

If one cut an onion, or other sharp food, with a fleishig knife, he may not eat it with cheese[22] רמ"א צו, א . If one is unsure which knife was used to cut it, the onion may not be eaten with milk or meat[23] דהוי ספק דאורייתא .

If one cut a pickle with a milchig knife, or poked it with a milchig fork, it should preferably not be eaten with meat[24] משום שיש לספק אם מיקרי דבר חריף או לא . However, if one does not remember which pickle it was, or it was already mixed with other food, it may be eaten with meat[25] דבטל ברוב .

If a fleishig (or milchig) utensil remained in a sharp liquid, such as vinegar, for five minutes, the liquid draws out flavor from the utensil, and should only be eaten with that type of food[26] שיש לספק כמה שיעור כבוש בדבר חריף, והוא "כדי שיתננו על האש וירתיח" (קה, א), וע' דרכ"ת (ס"ק מב) מחלקת אם השיעור ח"י דקות, או לא פחות מששה דקות, וי"א אין אנו בקיים. .

One may purchase cut-up fruit or vegetables from a non-kosher store^[27] רמ"א צו,ד, כיון שאפי' אם חותכו בסכין שחתך בו איסור, לא יהיה שמנונית בעין אלא על קצת מהם, והם בטלים . However, one should not purchase cut-up lemons or other sharp foods.

If one buys a soda at a non-kosher restaurant which contains a lemon slice, he may drink the soda, but he should not suck the lemon[28] דאפי' אם חתכו אותו עם סכין של איסור, לא אמרינן חתיכה נעשה נבילה, וכיון שיש רק כמות מועטת של לימון בתוך הסודה, המיץ הוי בטל בששים. .

C. Sinks and Dishwashers

One should not put milk and meat dishes in the same dishwasher, even if it is not used for both simultaneously[29] . If one did put them in together, the utensils are permitted and the dishwasher may still be used for whichever type it is designated for[30] .

If one found a milchig spoon at in the fleishig sink, or scrubbed it with a fleishig sponge, the spoon is permitted in many cases. The spoon may have not come in contact with water directly from the faucet, in which case the secondary spray (kli sheni) would not be able to create issur. It also may have not come in contact with water that was 112 degrees Fahrenheit, which would also not present an issue. If it did, this may have happened while there was soap in the water or on the spoon, which would also not assur the spoon. If one knows with certainly that one of these certainly happened, a Rav should be consulted.

If one finds a milchig utensil among his fleishig ones (or vice-versa), the utensil is permitted, because they may have not been washed together, and even if they were, the aforementioned doubts apply[31] .

D. Ovens

An oven must have a standard use of milchigs or fleishigs. One is permitted to use the oven for the opposite type of food, or food intended to be eaten with the opposite type, if the food is either covered[32] (e.g., with aluminum foil) or dry[33] אג"מ יו"ד א,נט (e.g., bread).

If one cooked pareve food (e.g., bread) uncovered in an oven simultaneously with meat, he may not eat it with milk[34] רמ"א (קח, א). ואם אין לו פת בריוח, מותר, דהוי כדיעבד (שם). . However, if one cooked uncovered pareve food in a clean fleishig oven, it may be eaten with milk. (“Clean” means no edible residue remains, even if there are charred remnants stuck on the bottom of the oven.) One may even cook pareve dry food, such as bread or cake, in a fleishig oven (immediately after cooking meat in the oven, but not simultaneously), intending to eat it with milk[35] רמ"א (שם), דלא מצינו ריחא ופיטום מכלי שיחזור ויפלוט לאוכל (ש"ך סקי"ב). וע' פמ"ג (שם) שאין לבשל בו לכתחלה, וע' בדי השלחן. . One may also cook covered, liquid dairy dishes in a clean fleishig oven.

If one cooked meat in a clean milchig or non-kosher oven, the meat may be eaten, and a Rav should be consulted regarding the status of the oven. If one baked milchig food simultaneously in the oven with fleishig food, the foods may be eaten[36] צז, א. דריחא מותר בדיעבד. . If one baked it with pareve food, the food should preferably be eaten with the type of food it was baked with[37] ? דהוי כלכתחלה, ע' רמ"א קח, א .

If one baked pareve food in an oven after milk or meat was baked in it, the food remains pareve and may be eaten with the other type[38] .

E. Going on Vacation

If one plans on storing his meat and dairy products in the same ice chest, both of them should be double-wrapped in order to avoid potential issues of kavush[40] ע' שו"ע (קה, א), ועמ"ש לקמן {הל' תערובת בענין כבוש} (items soaked together).

One who wants to heat up food in a non-kosher oven or microwave may double-wrap the food and then heat it. If, accidentally, it was heated in an oven without a covering, the food may be eaten. If it was heated in a microwave without a covering, a Rav should be consulted.

One may not use any utensil with a piercing action, such as a fork or knife, even on a temporary basis, without prior kashering[41] ואם רוצה להשתמש בו באופן עראי, צריך נעיצה בקרקע קשה. ויש מקילים דדי לשפשפו עם steel wool. אבל באופן קבוע צריך הגעלה. . One may use a non-kosher spoon, plate, or pitcher[42] אבל אין להשתמש בו בקביעות בלי הגעלה כיון שאפשר שהעכו"ם נתן בו מיץ ענבים ונעשה כבוש, ע' רמ"א (קכא, ה) וש"ך (שם ס"ק יג). for cold food temporarily without prior kashering (if clean from residue). However, one may not use it for hot food, or for an extended period of time for cold foods, without prior kashering[43] רמ"א (קכא, ה) .

Before first use of a non-kosher countertop or table, one should thoroughly wipe the counter beforehand to ensure it is clean from all residue.

When using a (non-kosher) sink for both meat and milk, one must ensure before washing a dish that there is no residue of the other type of food in the sink, and one should try not to let the dish touch the sides or bottom of the sink. If it does touch the sink, the utensil is still kosher[44] אג"מ (יו"ד א, מב) .

Regarding kashering utensils, microwaves, ovens, stove grates, grills, and other items, see {Chapter on Kashering}.