Pasteurisers and What They Achieve

Two plants pasteurise at the same temperature for the same time and get different halachic results. The difference is not the thermometer — it is whether the system is open or closed.

That is an unusual situation in kashrus, where the answer usually follows the material. Here it follows the equipment, and it is worth understanding before you specify a line.

What mevushal actually requires

For wine, boiling confers mevushal status, which removes the handling restriction. Two conditions attach, and the second is the one that matters here:

1. It actually boiled.
2. It diminished in volume through that boiling.

Hold that second requirement next to what a modern pasteuriser is designed to do.

The closed system is engineered against it

A closed pasteuriser runs the product through sealed pipework. Nothing evaporates — that is the point of the design. Producers go further and deliberately engineer the process so that the taste does not change at all, because a detectable change would be a defect.

So a closed system is built, on purpose, to prevent exactly the two things that ordinary cooking does: driving off volatiles, and reducing volume.

That is the heart of the stringent position on pasteurised wine. Ordinary boiling loses alcohol immediately and changes the character of the wine. A closed pasteuriser that only kills organisms, leaving the product organoleptically identical, is hard to call cooked — and the observation offered is that ordinary drinkers cannot tell pasteurised from unpasteurised at all.

The lenient position holds that heating is heating, and that the distinction between methods of heating was never drawn. Both positions are held by major poskim, and the dispute is live.

The open system does something different

Grape juice production shows the contrast, and the reason is a process requirement rather than a halachic one.

Juice is preserved with bisulfite to stop it fermenting. Before bottling, that has to come back out — so the juice is boiled in an open system, driving the gas off into the air or into lime water that captures it. Some installations run a second pump to return the water vapour to the juice after the gas has been scrubbed out.

Wines, by contrast, are often pasteurised in a closed system precisely so the vapour returns and the volume does not drop. Nobody wants to lose product.

So the two systems exist for ordinary commercial reasons, and they happen to land on opposite sides of the mevushal question. That is the useful thing to know: the halachic outcome was decided when the line was specified, by an engineer who was not thinking about it.

The argument that the exemption has expired

There is a further point that matters more to producers than to anyone else, because it is about market structure.

Mevushal wine was never included in the original decree, and the stated reason was that it was uncommon — drunk occasionally, in small quantity, not found in every house. The exemption tracked rarity, not any quality of the wine.

The stringent argument observes that this has simply stopped being true. If essentially all wine is now pasteurised before it leaves the winery, the condition the exemption rested on has gone. This is not presented as adding to the decree — it is the claim that the thing which kept pasteurised wine outside it no longer holds.

Whether that argument prevails is above our pay grade and belongs with your certifying rav. What it means practically is that a producer cannot treat "we pasteurise" as settling the question, in either direction.

What to establish before you build

If mevushal status matters to your product — and for wine and grape juice it usually determines your addressable market — these are the specification questions, and they are cheaper to ask at design stage than after commissioning:

• Open or closed? And if closed, is there any point at which volume is deliberately lost?
• Does it boil, or does it hold below boiling? Holding at 85°C is not the same claim as boiling.
• Is there measurable volume reduction, and can you evidence it?
• Which position is your certification working to? Ask explicitly — the two positions give different answers for the same line.
• What happens before the heat step? Boiling protects wine a non-Jew has not yet handled; it does not repair wine that was already handled. See supervising a winery.

That last point is the one that catches retrofits. Installing a pasteuriser does not launder the upstream process — it changes the status of wine going forward, and only if the upstream chain was intact.

These are general principles rather than a ruling on your plant. What your line achieves is a question for your certifying rav and your coordinator.