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I recently made chocolate pudding by putting 25ml of cream, 410ml of 3% milk and 50ml of cornstarch (not a good way to measure cornstarch, I know) along with two handfuls of Callebaut milk chocolate into the bowl of my Kenwood Cooking Chef, set it to constant slow stir (stirring speed 1) and set the cooking temperature (this stand mixer can cook in the bowl, while mixing) to 94 deg C. After a while I reduced the stirring speed to "once in a while" slow stir (stirring speed 3).

The result was really great but I wanted to redo it with even more chocolate to get a more saturated choccy flavour.

This time, same measurements, save for the choccy, of which I put in 169g, which seemed like more than double the last time.

This time I found out the gelatinization temperature of cornstarch is 60 deg C, so I set it to cook at 70 (just to be safe). It did not thicken at all. Thinking maybe it will after refrigeration I put it in the ol' fridge but all that happened was that a very thick surface coating was created. From experience with Creme Brûlée, I think it's the fat in the chocolate that accumulated and solidified at the top.

Put it in again in the bowl, added about 100ml more of starch and set it to stir at 68 deg C.

(BTW from experiments with the same starch and water I can, indeed, confirm it gelates at ~60 deg. C)

It's still cooking but I was wondering - is there some reason adding more chocolate made it harder for the starch to gelate?

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The problem is not the chocolate, it is the temperature.

I don't know what exactly you refer to by "the temperature of starch gelatinization" - the gelatinization of starch is a long, continuous process, that happens long after the starch has swollen and thickened. It is the process that is responsible for bread going stale - but not the process of thickening.

To thicken starch, you have to take it to temperatures between 90 and 100 C - the exact temperature differs between starches from different plants, and I believe is also somewhat dependent on processing. Some need 96 C, for others, 94 C is sufficient. The most common thing is to simply let the starch boil visibly, until you see bubbles form and plop, and then take it away from the heat.

The amount of chocolate shouldn't be a problem for the starch, there are many dishes which are slightly thickened with just a tiny amount of starch mixed into a main liquid with lots of fat or other ingredients, and they work perfectly well.

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  • I'm referring to en.wikipedia.org/wiki/Starch_gelatinization, https://www.sciencedirect.com/topics/food-science/starch-gelatinization#:~:text=During pan bread baking%2C starch,water move to the starch. and bakerpedia.com/processes/starch-gelatinization. Although, I admit I haven't read them just glanced. Also I refer to me putting water + a lot of starch in the bowl and observing how at 60 it turned to a pudding texture. – mummy May 31 at 18:56
  • The first source only says " Some types of unmodified native starches start swelling at 55 °C, other types at 85 °C, without defining a single "gelatinization temperature" - the numbers are about "start swelling", the granules are far from bursting yet. The second one says "The amylose and amylopectin fractions start to solubilize at 158°F (70°C) and 194°F (90°C), respectively." so they agree that you will have to bring it above 90 C to start the process. Also, in the graph, you see that the starch bursts after what they call "gelatinization temperature". Personally, I haven't observed the... – rumtscho May 31 at 19:25
  • ... slurry reaching a peak of viscosity and then thinning before it bursts and turns to actual pudding, maybe there are some minor differences which are measurable but not noticeable. I also don't know what you noticed at 60 C, maybe the transition from a pure suspension to the starting of swelling - but it is unlikely to have been the completely thickened state cooks want in a pudding, that one certainly requires the full bursting at over 90 C. – rumtscho May 31 at 19:28
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    yeah, increased temperature and it did the trick. -_- Sorry, seems I was fooled by the starch starting to swell at 60 and thought "oh, my, this must be it!". – mummy May 31 at 20:31

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