Kashering a Food Plant

Kashering a plant is not a bigger version of kashering a kitchen. The halacha is the same; what changes is that a plant is a connected system, and the parts of it that matter are usually the parts nobody thinks of as equipment.

The survey comes first

Before anything is kashered, the whole plant is walked — from the raw-material stores, through every production stage and every machine, to the packaging of the finished product.

Each item is then determined individually: the machines, the vessels, and — the ones most often missed — the pipework. For each, two questions: what its status is, and whether it can be kashered at all.

It is worth being clear about why the survey runs to the packaging line rather than stopping at the cook step. Product picks up status from anything hot it contacts, and a filler, a chute or a transfer line is contact. A plant that kashers its kettles and not its downstream pipework has kashered the part that was easiest to think about.

Equipment that cannot be kashered

Some will not survive it, and some cannot take it in the first place. Where that is the finding, two things follow:

1. Flag it, and supervise that it is not used. An unkasherable machine left on a certified line is the same failure mode as an unlabelled forbidden pot in a kitchen — someone will use it.
2. If it is necessary to production, either find a replacement, or put the question to a competent posek. Do not design around it privately.

This is the step most worth doing early, because it is the one with a lead time. Replacing a machine is a procurement decision, not a scheduling one.

The twenty-four hour problem, and how plants solve it

Kashering requires the equipment not to be ben yomo — a full day must pass without use. For a plant that cannot simply stop for a day, that looks like an impossible requirement.

The practice is a neat piece of scheduling rather than a leniency: kasher on the day after the plant's existing idle day.

• In Israel, kasher on Sunday — the plant did not run on Shabbos.
• Elsewhere, kasher on Monday, where the plant did not run on Sunday.

The day you are already down supplies the twenty-four hours. Nothing has to be created for it; it has to be noticed. If your site has a fixed weekly idle period, that is where a kashering belongs, and building the schedule around it costs nothing.

Boiling water, not process liquids

Food machinery is kashered with boiling water. Not oil, not fat, not the product itself. Where someone has kashered with another liquid, the kashering is repeated with water.

This causes genuine difficulty on lines that water would ruin, and that problem has its own page — when your process cannot tolerate water. It is worth reading before proposing an alternative, because most of the obvious alternatives have already been tried and considered.

Steam and vapour rising off boiling water are not accepted as a kashering medium either, though some permit it where the absorption itself happened that way.

A machine that needs libun but cannot take it

Where a machine requires libun and cannot be brought to that heat without being damaged, there is a defined route:

1. Clean it exceptionally thoroughly — no grease and no soiling left in evidence anywhere. This step is not optional, and the reason is precise: for visible residue, waiting twenty-four hours does nothing. Age degrades absorbed taste; it does not degrade a deposit.
2. Leave it twenty-four hours unused.
3. Run it at the heat it normally bakes at.

The first step is where these fail in practice. Scraping is the work; the waiting is free.

Places boiling water does not reach

Every kashering has a geometry problem, and in a plant it is usually a joint.

Lids attached by hinges are the standard example: forbidden material — or chametz — sits absorbed at the point of connection. Before kashering, dismantle them and clean them properly, and give libun kal to anywhere a hand cannot reach to scrape.

The same applies to any part of a vessel that the boiling water will not reach. Either libun kal there, or pour hot water over the spot and pass a glowing stone or glowing iron across it so the water actually boils at that point. Where a lid cannot be dismantled to go into boiling water, it gets the same treatment.

Which is a useful way to audit a proposed kashering: trace where the water will physically go, and treat everything it misses as a separate job.

What this means for scheduling one

Practically, a plant kashering has three lead times that do not overlap, and planning fails when they are treated as one:

• The survey — has to happen far enough ahead that an unkasherable machine can still be replaced.
• The idle day — fixed by your production calendar, not by anyone's convenience.
• The cleaning — the real labour, and the step that decides whether the kashering works at all.

Steam-cooked plants have a further constraint again, because the system holds water that must itself be turned over, and that alone can take more than a day.

These are general principles, not a ruling on your plant. What your equipment needs is a question for your certifying rav and your coordinator.