It scorched

Why it happens to thick products

The same conduction problem as the jar, one step earlier. Thin liquids circulate and carry heat away from the bottom; thick ones do not, so the bottom layer sits against the element and cooks far past the rest.

What it costs

• The burnt layer, which is product you bought.
• The flavor of everything above it, which is harder to admit.
• The time to scrub a kettle that is now the constraint on the next batch.

Avoiding it

Heat you can control at the bottom rather than at the maximum, constant movement through the reduction rather than occasional stirring, and a vessel sized so the product is not a deep column over a small element. Steam-jacketed equipment exists precisely because of this problem and it is usually the first serious purchase a growing sauce maker makes.

Do not try to rescue it

A scorched batch does not come back. Decanting the good part off the top carries the taint with it, because the flavor compounds are already through the product rather than sitting on the bottom. Decide that rule in advance, because the moment to decide is not while looking at a day of work.

It is the clearest signal that the kettle is the constraint

Scorching usually arrives at the moment a maker starts pushing batch size in the equipment they already have, because a deeper column of thick product over the same element is exactly the condition that causes it. That makes it an early warning rather than only a loss: it is the operation telling you which piece of equipment has to change before the volume can. Growing through it by stirring harder works for about one season.

It is also the failure most likely to happen on the biggest day of the year, because that is when the kettle is fullest and the attention is thinnest.

References