Hi Richard,

So I first came across this technique from someone who had spent a lot of time in Russia, and the more I researched it the more common I realised it is in that tradition. It works on many different levels.

Essentially, when you scald flour above 72°C you kill the enzymes in the flour. This means the enzymes in the sourdough don’t have to fight against the indigenous enzymes in the rye. The sourdough enzymes can then speed up the rate at which the sugars and specifically the pentosans are made available, and that speeds up the rate of fermentation. The accelerated rate of rye metabolites produced by the bacteria increases the sourness.

Now of course, if you’re looking for a slightly sweeter bread you want to prevent that sourness running away, and the way I balance it is by using a huge amount of cold starter in my rye, so it kind of balances itself out once the cold starter is in. The combination of the scald, the absence of indigenous enzymes, and that cold starter creates a sweeter version of a rye, especially if you then add malt or anything sugary.

It’s worth saying that the Russian zavarka tradition often goes a step further than a simple scald, pre-fermenting the scald itself with a small amount of starter for several hours before bringing it into the final dough. That gives you a sweet-sour layer of complexity in the finished loaf, because the gelatinised starches in the scald feed a slow, controlled fermentation that develops sweet, malty notes alongside the sour coming from the main dough.

The cold starter has a second effect that’s worth understanding. Cooler fermentation temperatures shift the bacterial balance towards more lactic acid and less acetic, so the sourness you do get is rounder and yoghurty, which is another reason cold rye doughs taste sweeter even at high inoculation rates.

There’s a Maillard angle here too. Scalded ryes develop a deeper crust colour and more complex caramel-malt notes, because the gelatinised, partially-hydrolysed starches sit there ready to react the moment the loaf hits the oven.

And for rye specifically, the pentosan story is as much about structure as it is about fermentation. Pentosans hold many times their weight in water, and scalding unlocks that water-binding capacity, which is a big part of why scalded ryes have that dense, moist, almost gelatinous crumb that keeps for days.

Vanessa