Fudge Fail Could it be doubling ingredients

Question

I know this is a common question. But I am getting different results with each batch. But I did double my ingredients, hit the correct temperature but still ended up with a pliable toffee. will try and post a pic.Recipe: 6 x tins condensmilk (385g), 2.4kg Castor Sugar, 150ml Golden syrup, 450ml Water, 360g Salted Butter, 30ml Vanilla. Method: disolve water and sugar over a low to med heat (gas bottle with plate), add syrup and butter until melted, add c/milk. keep stirring. Temp hit 114, turned heat down and kept it at that temp stirring for another 5min. Took off the heat added vanilla and stirred / beat for a further 3min. Poured into tray and ended up with a pliable toffee. I made a batch with half the ingredients and it ended up perfect. I am looking for a hard fudge and not a soft american fudge. I am flumoxed and a tad frustrated as I hit the correct temperatures etc. Both batches were made on the same day, so the weather was not an influencer, Hopefully someone can shed some light. tks a mil

Answer 1

My guess would be that it is a temperature issue. How did you measure the temperature?

You have roughly 4 kg of ingredients, so the temperature will not be the same everywhere. Of course the stirring is supposed to resolve that but the amount of stirring needed for that also scales with the quantity of the ingredients.

Additionally the surface to volume ratio changes when you double the ingredients. A bigger batch will cool down slower, especially while still in the pot. A different pot would also have a different heat capacity.