Kashering Of HTST Systems-Plate Pasteurizers

Many of our plants feature kashering of HTST plate pasteurization systems. It is particularly common for this kashering to occur via automated CIP, whereby the CIP system is programmed to operate at kashering temperatures.

Unless such a CIP system is set up very meticulously, there is a significant likelihood that it will not kasher. Please allow me to explain.

The typical automated CIP kashering system includes a caustic wash at 190 F or above to achieve pegimah, followed by a fresh water flush at 200 or so (high of 212 and low of 190), which is the actual hag’alah. (If there will be 24 hours of down-time before the fresh water hag’alah, there is no need for the caustic to provide pegimah.)

There are some areas of an HTST system which are not necessarily included in every CIP as set up by the plant, and which often will not be included in a hot fresh water flush. These areas – the divert system, including the balance tank, as well as the cooling section and leak detect valves – are not intended for full, normative hot product flow, and they will often be cleaned at lower temperatures and thus not kashered properly, unless we specifically program for them to be kashered as required.

It is thus important to communicate and verify with our plants that have CIP kashering of HTST systems that the divert and leak detection valves be opened periodically during each phase of kashering, and to specify and monitor that the cooling section likewise be subject to both phases of kashering. This will assure that the entirety of the system is kashered as per the stages and temperatures that we require.

Rabbi Stone, who provided most of the following information and has an extremely impressive mastery of this topic, cautions that RCs and RFRs should only address this issue with companies once the RCs and RFRs are sufficiently proficient in the matter, as major michshol can otherwise result. RCs and RFRs who need guidance should always consult with those who have the requisite proficiency before making changes in CIP/kashering systems.

The only effective method for educating about this important issue is on-site training; this memo is merely an overview.

That having been said, let’s turn our attention to how HTST systems work and the kashering that they require.


Although during normal production, we encounter the balance tank as operating at cold temperatures, the balance tank actually is a hot-use vessel, for when plants start production, they recycle hot product through the system, including the balance tank, until the system’s heat is sufficient to make finished product and send it to the filler for packaging.

Typically, during start-up, product will leave the balance tank, become pre-heated in the raw regen area, then be pasteurized and held hot in the holding loop, after which it begins to be cooled in the pasteurized regen area. Product then proceeds through the cooler, which may be turned off at this point. Product is then diverted back to the balance tank, often quite hot.

During regular production after start-up, product is cooled after exiting the holding loop, and the balance tank does not get hot – unless hot product which needs to be reheated is diverted there.

In sum, the balance tank is initially exposed to hot product and needs to be kashered.


During CIP, the balance tank will be subject to some hot caustic water, but likely not enough to kasher or perhaps even be pogaim it. This is because the CIP features very brief pulsation of divert valves, in which the valves which can divert product that has been heated (and not yet cooled) back to the balance tank are opened; however, the valves are opened for very short intervals (usually 30 seconds), likely not enough to overflow the balance tank with roschin (boiling water) or anything close.

The cooling sections of the system are off during CIP, and caustic water circulates through the whole system, including the balance tank. However, this water is often not roschin when it gets to the balance tank, as by the time it exits the heating sections and travels through the pasteurized regen and cooler, this water is commonly below roschin temperatures, only after which it then reaches the balance tank.


When kashering, it is thus necessary to assure that roschin water will indeed enter (and overflow, or at least maximally fill) the balance tank. How can this be achieved?

The answer is by opening the divert valves during part of the kashering for intervals of several minutes, so that roschin water, freshly heated to the maximum by the heating unit, will go directly to the balance tank (rather than arriving there after a full loop through the pasteurized regen and cooling areas, where it loses temperature even if these areas are not cold). However, the valves cannot be open for all of the kashering, as otherwise the water will not get through the rest of the system, leaving it unkashered!

Again, the cooing section must be turned off for kashering.


How does one know that the divert vales were opened for part of the kashering? There are two ways to determine this:

a. The outer area of the Taylor chart, around its perimeter, often has a pen line, which features a solid line that does not fluctuate. This line measures the divert valve: when the valve is closed, the line is in one position, and when the valve is open, the pen line drops at a 90-degree angle and turns at 90- degree angle, so as to create a clear indentation. This indentation shows that the divert valves opened or closed. One can thus tell that the valves were open and closed and for how long.

b. Every valve has a number, as does every pump and every piece of equipment in the system. The number identifies the valve and shows where the order was sent. Thus, one can use a CIP pin chart or computer graph to show the opening and closing of each valve. One must identify the relevant valves that need to be opened – and one needs to be trained to be able to read a CIP pin chart or computer graph for this purpose.

Please note that every system features two temperature probes – one at the end of the pasteurization holding tube and one at the exit of the cooling system.

Also, typically, divert and leakage valves open and close in tandem.

This memo is a mere overview for those who asked to know more about these systems; it does not suffice and cannot act as a training tool.

Please consult those who have mastered this topic for guidance toward implementation.

OU Kosher Staff