I'm a new user, but after a fair amount of searching on Chowhound and elsewhere I've still not found a clear answer to understand how much of an impact the material of a roasting pan might have on cooking times. My question arises from a very specific case: on two recent occasions, I cooked a 1.5 kg boneless Angus rib roast under essentially identical conditions but in two different roasting pans, and the time taken to reach the right internal temperature was way longer the second time round.
The joint was bought from the same source and essentially had the same dimensions, and in both cases I was aiming for medium-rare and roasted at 120°C for 30 min per half kg (so total roasting time 1.5 h). I tested with a thermometer within the final half hour to reach an internal temperature of about 48°C, then left it to rest before doing a brief final sear at high temperature just before serving. The joint was never frozen, and I took it out of the fridge and left it at room temperature 1–2 hours before roasting.
The first time round I used a cheap, thin, Teflon-coated roasting pan (not sure of the material, but it's slightly magnetic, so presumably steel). The coating means it is dark-coloured inside and outside. The result was perfect: 1.5 hours was just right to reach 48°C.
The second time round I used a slightly heavier stainless steel roasting pan that was not coated, so was shiny metallic inside and out. This time, after 1 h 10 min, the internal temperature was still only 29°C, and with guests about to arrive, I raised the temperature to 150°C and kept testing regularly. But it took another 1 hour 5 min to reach 48°C internally. I noticed that the top seemed to be cooking somewhat faster than the bottom, so I turned the joint round part the way through. In total, it therefore took 2 h 15 min rather than the 1.5 h the first time. On the second occasion, I was actually even more careful to give the joint a full two hours outside of the fridge before roasting, so I can't imagine that the starting temperature would have been very much lower the second time round (where I live, room temperature means around 27–29°C year-round).
Both times the position within the oven was the same, the thermometer was the same, and I even calibrated the thermometer in ice water and in a boiling kettle (0.4°C and 99.5°C). The oven was set to top and bottom heating, with fan.
After worrying that maybe my oven was malfunctioning, I bought a two-probe digital oven thermometer and tested the temperature at the top and bottom across a range of temperatures, and it was typically within 5°C of the set temperature both when set to 120°C and at 200°C.
So, the only real difference that I can identify was the material of the roasting pan. I've read many websites that say that pure stainless steel has poorer heat conduction, and the dark Teflon coating on the old roasting pan should have helped heat absorption.
But is it really possible that the material of the roasting pan could have made such a large difference to the cooking time???
Many thanks in advance for any helpful comments!
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