You can find Part I of this essay, here.
A typical takeaway food dish, aluminium body with cardboard lid and filled with about 300 g of water was used as a simulacrum of a TV dinner:
The oven was set to 200 C.
The oven temperature ('Toven') and food temperature ('Tfood,cold' and 'Tfood,cold') were then measured at 10 minute intervals. The results are represented below, graphically:
Slightly surprisingly, there apears to be very little difference in temperature evolution between the use of a preheated oven ('Tfood,hot') and a non-preheated oven ('Tfood,cold') This may in part be explained by:
1. the food tray is aluminium, an excellent heat conductor,
2. the content is a pure liquid, which tends to heat faster than a pure solid,
3. 300 g is less than the more typical 500 - 800 g for a TV dinner,
4. the required heating time seems significantly lower than the one generally recommended by various outlets ('20 to 30 minutes') This may be due to said outlets 'playing it safe'.
It appears thus that it's worth for individual consumers to experiment a little with heating times of various foods, because substantial savings in heating times and thus £££ may be made.
Damn, and I thought I was saving so much time in skipping the pre-heat...
ReplyDeleteSo the "takeaway" is to follow directions vis. time and not add cooking time when starting with a cold oven?
ReplyDeleteWould your experimental results have been substantially different if the final food temp had been 100C requiring you to effect a partial phase-change (enthalpy/latent heat of vaporization) water to steam? The last degree of temperature would take more time (or needed added pressure)...
ReplyDeleteIt would be interesting to note the two differences in total cooking time based upon when the last bit of water turned to steam...
DeleteSorry, didn't see these comments until now.
ReplyDelete#1: you can save time and energy by skipping the pre-heat pahse. Just monitor final temperature, then make a note for that particular food.
#2: yes, results seem to indicate it's favourable not to preheat, as I've been doing for some time now. Again, monitor final temperature. I use a, IR gun probe now (also useful for probing guests on Covid!)
#3 and #4: it's academic. 100 C is far too high and would scorch most things like pasta or taters. 75 - 80 C is now considered ideal but I believe just north of 70 C is fine too.
I didn't know that... I'm not much of a cook. I'm more of a "popcorn" kinda guy. ;)
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