Earlier today, Lauren posted a question on Rose’s blog about why the microwave and not a conventional oven is used in the preparation of kate flour. Although this isn’t the first time I’ve been asked this question, I haven’t actually tried heat-treating flour in my own oven until now. As I responded on Rose’s blog:

I haven’t tried heating flour in a conventional oven (yet!), but I have read about it. In relation to pancake springiness, heat-treatment at 120 degrees C for 2 hours in an oven has been shown to have the same improving effect as chlorination (Seguchi, 1990). Interestingly, incubation of starch granules at room temperature for 233 days also has the same effects on the starch granule’s oil-binding capacity (Seguchi, 1993). However, more recent scientific analysis suggests a different mechanism of starch gelatinisation when the granules are heated in a microwave compared to conduction heating (Palav & Seetharaman, 2006). Microwave heating (but not conduction heating) results in granule rupture, which in turn has an effect on the rheological behaviour of the dough or batter.

Lauren then asked about how to avoid the ‘toasted’ taste when microwaving flour, which is something I have also been thinking about for some time now. Chocolate cakes are one way of masking the flavour (and they always find an appreciative audience among my children), but it would be lovely to be able to solve the ‘colour or crumb‘ conundrum.

It’s funny how the majority of my flour experiments took place whilst builders were working intensively on our home last year. Perhaps the arrival of our plumber this morning acted subconsciously as the final call-to-action today. Whatever the spur, it wasn’t long before 10 oz of soft 00 grade flour was in the oven at 120 degrees C for 2 hours!

From some distant reading, I also recalled an invention in which pharmaceutical substances were prepared in a microwave without scorching by means of continual tumbling (if anyone finds a reference for this memory, do let me know –  I didn’t bookmark the source when I first came across the information). I wasn’t up for continual tumbling today, but I did wonder if perhaps the toasting problem was a result of too little agitation during heating. Now, I have been known to shout and rant a bit at electrical appliances in the past, but I opted instead to agitate the flour every 10 seconds by opening the microwave door and swirling it quickly with a fork. It took about 10 minutes of microwaving-time (which equates to about 18 minutes of preparation time) before the flour reached 130 degrees C.

Here are my 3 different flour-treatments of today: to 130 degrees C with 1-minute agitation in the microwave (top-left); to 130 degrees C with 10-second agitation in the microwave (right); 2 hours at 120 degrees C in the oven (bottom-left).

As well as being less toasted than the less-agitated microwaved flour, the whiter-microwaved-flour also produced considerably less wastage on sieving:

I then proceeded to bake cakes using the 2 whitest flours: one lazy lie-in from the oven; one greatly-agitated from the microwave. I am excited to report that both flours produced a yellow butter cake without any taste of toasting and far beyond anything that can be achieved without flour-treatment.

In terms of vital statistics, the microwaved-flour cake rose just over 1 cm higher than the oven-flour cake and had a slightly finer, more delicate crumb. Although today revealed a choice of flour-treatment, for me the ‘battle’ is won by the microwave on two counts: crumb and environment (apparently, the microwave uses about 75% less energy than a conventional electric oven).