A Kosher Formula

I have heard it said that running a successful kosher program is as easy as PIE: Products, Ingredients and Equipment. One must keep an updated schedule B (products) an updated schedule A (ingredients) and have a proper system for keeping track of the kosher/pareve status of equipment. I would like to add another interpretation to this wise adage. Running a successful kosher program is as easy as π (as in 3.14159…).

Product formulas are not the only formulas that one needs to understand in assessing a kosher program; sometimes we must employ mathematical formulas as well. If we are required to verify the volume contained inside of a pipe we must understand the formula V= πr2h. If we must figure out the volume of the metal of the pipe we must understand the formula V= πh(R2- r2). And if we need to know how much product flowed through a pipe, well, it can get complicated very quickly.

In a more complex question relating to inlet and outlet flows, we consulted with Dr. Don Engelberg, Professor of Physics, Queensboro Community College in New York. We needed to answer the following question. Oil was drawn off a tank at a certain rate and was being replaced at a different rate. In this case the kosher status of the equipment would be determined by whether or not most of the original oil would be replaced within 24 hours.

If, for example, the tank initially held 400 gallons of oil, had an intake rate of 10 gallons/hour and an outlet rate of 12 gallons/hour, would the tank remain kosher? Dr. Engelberg crafted for us the following formula for answering this question.

X = V * (1 + ((I – O) * T / V))O/(O – I)


X = Volume of old oil left at the end (in gallons)

V = Initial volume in tank (in gallons)

I = Intake rate (in gallons per hour)

O = Outlet rate (in gallons per hour)

T = Time elapsed (in hours)

In this case V = 400; I = 10; O = 12 and T = 24. Solving, we find that the volume of old oil left at the end (X) = 186 gallons. Since this is less than half of the original amount, the tank will remain kosher. Easy as pie.

Rabbi Eli Gersten serves as OU rabbinic coordinator – recorder of OU policy. In that important capacity, he works closely with the OU’s senior rabbinic team that reviews and formulates OU Kosher policy. A frequent contributor to BTUS, his “The Science of Kosher Materials” appeared in the Spring 2010 issue.

OU Kosher Staff