You cook meat in a pot. You eat the meat, and clean the pot spotless. There is not a speck of meat left anywhere within
20 feet of it. Then you clean the pot again.
Although there is obviously no meat left in this pot, you
may not use it to cook dairy (Y.D. 93) This is the principle of
"Belios" are invisible "particles" that exist in food which,
under favorable conditions, travel from the food into just about
anything they come in contact with.
When meat is cooked in a pot, Belios of the meat travel into
the pot. This is what we mean when we say in Yiddish that a pot
is "Fleishig"; i.e. it contains Belios of Fleish (meat; "Milchig"
means "containing Belios of milk or dairy). When dairy is later
cooked in that pot, the Belios of meat travel into the dairy
product being cooked. Belios of meat have the same status in
Halachah as meat itself. A dairy product with meat Belios in it
is like a dairy product with bits of meat in it. In other words,
In addition, any food subsequently cooked in that pot also
becomes Treif. Consider: When the dairy product was cooked, its
Belios - dairy Belios - traveled into the pot. The pot now
contains Belios of meat and Belios of dairy. When something -
stringbeans, for instance - is later cooked in that pot, the
dairy Belios ”and• the meat Belios travel into the stringbeans,
making it Treif, as it now contains "particles" of both meat and
Although colorless and odorless, Belios do have a taste.
They taste exactly like the food they came from. In fact, a
"litmus test" to determine whether or not dairy that was cooked
in a "Fleishig" pot did indeed absorb meat Belios (or vice versa)
is to let a gentile taste the dairy; if he can not taste the meat
Belios, we may assume they are not there (Y.D. 93, Shach 1) (Note: In actual
practice, we do not rely on this "taste test. (Ramah, Shach ibid.)
Belios also take up "space." The total mass of all the
Belios in any given item can not exceed the mass of that item.
Meaning, a large meatball has more Belios than a small
Knowing the mass and volume of the Belios in an item
is important for determining "Bitul."
Another similarity Belios have to real food is that after a
while they spoil. The shelf life for Belios is 24 hours, after
which they putrefy and become unpalatable ("Nosen Taam Lefgam").
Spoiled, unpalatable Belios are considered Halachicly
"neutralized," and no longer retain the identitly of their mother
source. After 24 hours, meat Belios are no longer considered
like meat, and dairy Belios are no longer considered like dairy.
This means that if you cooked meat in a pot (thereby loading
it up with meat Belios), and 24 hours later boiled milk in it,
”the milk is 100% kosher•, because by the time the milk was
cooking, the Belios of meat were already spoiled, and lost their
original status as meat (Y.D. ibid.)
Important qualification of this Halacha: Chazal were
uncomfortable with the idea that people would be using their
Fleishig utensils for dairy after waiting 24 hours; a measure of
caution was necessary, they felt, to insure that real Fleishig
utensils would not be used for Milchigs and vice-versa. They
therefore prohibited the intentional use of any Fleishig utensil
for dairy, even if the meat Belios are already spoiled. After
the fact, if such a pot was used, the cooked dairy product may be
Similarly, if a pot contains Belios of both meat and dairy,
even if they are spoiled, it may not be used intentionally to
cook neither meat nor dairy, as intentional use of even spoiled
Basar Becholov Belios is prohibited. It is the custom to refrain
from using such a utensil even for Pareve (neutral) foods
(Ramah Y.D. 93, Shach 3, Ramah Y.D. 94).
Example: Reuven's wife never dreamed that her husband
would ever fix himself breakfast, so she never told him
which pots were Fleishig or Milchig. Believing a
certain frying pan designated for dairy, Reuven fried
his egg in it, with butter. As he was about to take
his first bite, Mrs. Reuven enters, visibly upset and
screaming something about that particular frying pan
being used only for chicken cutlets. The Halacha: If
the pan was used for chicken cutlets within 24 hours of
Reuven's frying his egg, breakfast must be thrown out.
If the last time Mrs. Reuven fried meat in that pan was
more than a day ago, the eggs may be eaten. ”However,
the pan itself, as it is now imbibed with Belios of
both dairy and meat, may not be used in the future for
any type of cooking (NOTE: What to do with the pot is a different issue).