--
Peter
Should I doff my chef's hat
You're missing an assumption about the average size and shape of a roast.
What really counts os the thickness or, more meaningfully, the depth to the
centre, of the meat. Because of the limitation imposed by the size of
domestic ovens (and therefore a certain conformity in the sizes of pieces
of meat that can be cooked in them), the weight/time equation works well
enough most of the time.
--
Peter
But, each of these cuts have the same depth to the center. The only significant
variant is the length.
--
Peter
Which was my point - the instructions make assumptions that are wrong, but
not sufficiently wrong not to work sufficiently well to get by most of the
time.
Cooks take reponsibility for most failures in the kitchen, so the
formulators of these "instructions" are never called to account..
--
Peter
A roast cooks from all surfaces inward; cut one in half, and you have
two surfaces that are now closer to the center, even if the other two
are not, so the cooking time does get adjusted as a result.
Also, no cooking instructions ever say to cook a certain time and leave
it at that; they all have tests for doneness.
--
-- DE
>>
>
>
> But, each of these cuts have the same depth to the center. The only
> significant variant is the length.
>
But you won't end up with the reddish centre part which is crucial to a
good roast!
--
Rectagon to eat
Goddamn. Am interfacial transfer question. For me, this is like someone
asking Karl a bible question, except I am going to get the answer right.
First, model each roast as a sphere. Then assume the thermal conductivity
of the roast is the same regardless of size. Next, assume that the heat
capacity of the roast is constant with size. Ok, so the total amount of
heat you have to get into the roast to cook it (i.e., raise its temperature
to some specified level (let's say 70 C for the sake of argument because
you like really dried out tough beef)) is equal to:
Heat = M * Cp * (Tf - Ti)
where M is the mass of the roast (g), Cp is the heat capacity (cal/(g-
deg)), Tf is the final temperature (C), and Ti is the initial
temperature (C). I am going to make a big assumption here and say that
temperature is uniform through the roast (it isn't really, but I don't want
to have to integrate the temperature profile (this assumption is really the
same as saying the thermal diffusivity is very fast compared to the time
required to heat the roast (I think anyway (which, come to think of it is
the same assumption that guy used to show that strong mantle overturning
generated the biblical flood so if it's good enough for Karl it's good
enough for me)))).
Ok, so you can see from the first equation that the total amount of heat
required to cook your roast is directly proportional to the mass. But
remember that the ratio of the surface area of a sphere to its volume goes
as the inverse of the radius. This is important because the amount of heat
you can deliver to the roast has to go through the surface and we are going
to assume the surface heat flux per unit area is the same regardless of
roast weight. That means it is more efficient to deliver heat to a smaller
roast in terms of surface area to volume.
If you want to do the math, you can figure the heat flux per unit area will
be given by:
Flux (cal/cm^2-s) = k*r*Cp*(Ta-Tr)
where k is the thermal transfer coefficient (cm/s) and r is the density of
the roast (g/cm3). To get the net heat per unit time going into the roast,
multiply Flux by the roast surface area.
Anyway, you either don't care anymore or see why it takes less time to cook
a smaller roast. The bottom line is the 20 min/lb is an approximation
where someone have gone through and done the calculations I outlined above
assuming a realistic shape for the roast (or maybe even approximating it as
a sphere) and real temperatures, heat capacities, diffusivities etc.
--
Bill "this was in my wheelhouse" Asher
> A roast cooks from all surfaces inward;  cut one in half, and
> you have two surfaces that are now closer to the center, even if
> the other two are not, so the cooking time does get adjusted as
> a result.
Harrumph. But the centres of the two halved pieces are not the
original centre - and their centres have, in fact, moved such
that they are closer to elements of the original surface(s).
(I'm still trying to enumerate your surfaces: the original had
two, and the two severed chunks have four. Enlightenment,
please, lest I wrestle in my sleep with this.)
Cut to the chase. Get a meat thermometer.
> First, model each roast as a sphere.
i haven't read the rest of your post because i stopped at this line. did
you know, there's an old joke that's a favorite of mine with the punch
line, "assume a spherical cow"? is that *really* what you just said
here, too? lololol...(well, maybe it's only funny if you know the joke,
and maybe not even then, sorry.)
h
> i haven't read the rest of your post
oops, i left out the word "yet". sorry :)
h
You know, if you were baking the roast in zero-g, it would be a lot more
spherical. So maybe it would make more sense if I said: "Assume you are
cooking in zero-g and that surface tension makes the roast nearly
spherical." There. Now it is not nearly so stupid a statement.
--
Bill "next time, you cook the stupid roast then" Asher
Here's the joke I know ...
A group of wealthy investors wanted to be able to predict the outcome of a
horse race. So they hired a group of biologists, a group of statisticians,
and a group of physicists. Each group was given a year to research the
issue. After one year, the groups all reported to the investors. The
biologists said that they could genetically engineer an unbeatable
racehorse, but it would take 200 years and $100 billion. The statisticians
reported next. They said that they could predict the outcome of any race,
at a cost of $100 million per race, and they would only be right 10% of the
time. Finally, the physicists reported that they could also predict the
outcome of any race, and that their process was cheap and simple. The
investors listened eagerly to this proposal. The head physicist reported,
"We have made several simplifying assumptions... first, let each horse be a
perfect rolling sphere..."
> William Asher wrote:
>
>>First, model each roast as a sphere.
>
> I wasn't going to talk to you anymore since you turned into a
> dick, but exceptions are my rule.
>
> Roast balls?!?!?
>
> Give me your address I have to send you a 22lb brisket.
>
> <snip weirdo-whacky thermal conduction equation>
>
>
I didn't turn into a dick, I just act like one. And it's not a new
behavior on my part anyway.
I could have modeled the roasts as cubes. The surface area to volume ratio
would still go as the inverse of the characteristic dimension of the cube.
If you wanted to do tetrahedrons, same thing. It becomes more
problematical if you are not talking about a platonic solid since there is
more than one characteristic dimension.
Couldn't you send me a goose instead. It might save Tiny Tim's life.
--
Bill "or you could turn the page" Asher
The bigger the roast (and, yes the longer the cooking time) the more
"rare" meat there is in the middle. You get to pick either well done
(on the outside) or rare (at the core). :)
--
Rectagon
> William Asher wrote:
>>I didn't turn into a dick, I just act like one. And it's not a new
>>behavior on my part anyway.
>
> That's why I carry a shortarm with a huge load (not to be confused
> with Karls new wide-load posts (or were those pant-loads)).
>
>>I could have modeled the roasts as cubes. The surface area to volume
>>ratio would still go as the inverse of the characteristic dimension of
>>the cube. If you wanted to do tetrahedrons, same thing. It becomes
>>more problematical if you are not talking about a platonic solid since
>>there is more than one characteristic dimension.
>
> Were you looking in your undies when you said that?
>
>>Couldn't you send me a goose instead. It might save Tiny Tim's life.
>
> No, you get brisket. Toss it somewhere hot and wait for grease to
> happen, then eat.
>
>
I thought you were just happy to see us.
It's undies-free thursday at work today. Which sucks cause it's
relatively cold today.
God bless us one and all.
--
Bill "bit on the brisket side" Asher
But here the roasts are shaped like a log
--
Peter
Getting log headed
> If I cut the roast in half I will get two 3 lb
> roasts, each as thick as the original.
As thick in which dimension? Anyway, get a meat thermometer.
--
Steve
> "Rectagon" <rect...@netscape.net> wrote in message
> news:11q3ot2...@corp.supernews.com...
>> Peter wrote:
>>> "Rectagon" <rect...@netscape.net> wrote in message
>>> news:11q3clm...@corp.supernews.com...
>>>> Peter wrote:
>>>>
>>>>>>
>>>>>
>>>>>
>>>>> But, each of these cuts have the same depth to the center. The
>>>>> only significant variant is the length.
>>>>>
>>>>
>>>> But you won't end up with the reddish centre part which is crucial
>>>> to a good roast!
>>>>
>>>
>>>
>>> ???
>>>
>>
>> The bigger the roast (and, yes the longer the cooking time) the more
>> "rare" meat there is in the middle. You get to pick either well
>> done (on the outside) or rare (at the core). :)
>>
>
>
> But here the roasts are shaped like a log
>
Peter:
For any solid object, the surface area to volume ratio increases as the
overall size decreases as long as the shape remains the same. When you cut
the big roast into two, you increase the surface area through which heat
can flow into the roast so it cooks faster. In your example there are now
two extra sides of the roast available for heat transfer, which is why it
is cooking faster. The example where you had the smaller piece and larger
piece, the smaller piece cooks faster because it has a higher surface area
to volume ratio than the larger piece.
Piece!
--
Bill "nobody listens to me" Asher
> But here the roasts are shaped like a log
That's what you get for buying a used one.
--
Steve
So, I wonder if it would cook faster if you cut it in half.
--
Rectagon to find a grizzly bear to poke with a stick
Yeah, but for ONCE I said it in simpler language!
*sigh*
No winning, I would pick a scientific discussion to finally find a
commonly concise response.
--
-- DE
> Here's the joke I know ...
the one you reminded me of is basically the same, but reading it might
make you feel better. (because it makes fun of those pesky math people
instead):
The USDA once wanted to make cows produce milk faster, to improve the
dairy industry. So, they decided to consult the foremost biologists and
recombinant DNA technicians to build them a better cow. They assembled
this team of great scientists, and gave them unlimited funding. They
requested rare chemicals, weird bacteria, tons of quarantine equipment,
there was a horrible typhus epidemic they started by accident, and, 2
years later, they came back with the "new, improved cow." It had a milk
production improvement of 2% over the original.
They then tried with the greatest Nobel Prize winning chemists around.
They worked for six months, and, after requisitioning tons of chemical
equipment, and poisoning half the small town in Colorado where they were
working with a toxic cloud from one of their experiments, they got a 5%
improvement in milk output.
The physicists tried for a year, and, after ten thousand cows were
subjected to radiation therapy, they got a 1% improvement in output.
Finally, in desperation, they turned to the mathematicians. The foremost
mathematician of his time offered to help them with the problem. Upon
hearing the problem, he told the delegation that they could come back in
the morning and he would have solved the problem. In the morning, they
came back, and he handed them a piece of paper with the computations for
the new, 300% improved milk cow.
The plans began: "A Proof of the Attainability of Increased Milk Output
from Bovines: Consider a spherical cow......"
heather
> So, I wonder if it would cook faster if you cut it in half.
Ask a Chinese cook with his wok.
Heh. Your wife is going to have a field day with this one!
I like Bill's post on the subject, especially as he imagines roasts as
spheres.
IMAO, most roasts tend towards either cylindrical or slab shapes; it is
not possible to enumerate surfaces without answering that basic
question, especially as a cylindrical roast will have 3 surfaces in
theory, but at least 4 in practicality (as the bottom is flattened thus
making it a plane it lays on, while the "sides and top" may form an arc.
This would substantially complicate the equations, especially as Bill
has insistently, stubbornly, unscientifically, penis-like as Karl might
call it, ignored critical issues of thermal transfer.
In fact, if one were to be so crude as to cook the roast in a (heaven
forbid!!!) microwave oven, the entire scenario and resultant analysis is
modified completely.
--
-- DE
<snip>
>
> So, I wonder if it would cook faster if you cut it in half.
>
Probably not in your case since you would likely forget to turn on the
oven.
--
Bill "cooking's a woman's work anyway" Asher
<snip>
>
> *sigh*
> No winning, I would pick a scientific discussion to finally find a
> commonly concise response.
>
It's not my fault you didn't simplify your answer by assuming the roasts
were spheres.
--
Bill "cutting corners to make meat ends" Asher
<snip>
>
> The plans began: "A Proof of the Attainability of Increased Milk Output
> from Bovines: Consider a spherical cow......"
>
Sometimes, just to hear the applied mathematicians snap their pencils in
anger, I will "solve" a simple differential equation of the form
dX/dt = aX(t)
by dividing through by X(t), multiplying through by dt, and then
integrating.
--
Bill "mostly I just keep my mouth shut till they get bored and walk away"
Asher
Had to expand any doorways recently? You know how these scientist types
are!
--
-- DE
I know a lion that works with!
--
-- DE
Which woman would that be?
I could use someone around the house to do it!
--
-- DE
>
> Which woman would that be?
>
> I could use someone around the house to do it!
>
The little one?
--
Bill "backpedal, backpedal" Asher
Stop Karling me!
--
-- DE
At least I didn't challenge you to a slam dunk contest.
--
Bill "I hate losing" Asher
new verb for the a.c. FAQ: karl (vt): to deliberately bait someone using
snide innuendo of an explicitly sexual, racial, or intellectual nature.
e.g. 1. Bill was karling Debra over her lack of prowess in the kitchen
and klingonesque sexual appetites.
(do I get bonus points for karling Debra in my definition of karling?)
DE,
This is why I hang out here. Only on alt.corel could a post that starts
with a cooking conundrum have a post like this.
C.
Yeah, but it didn't succeed in trolling Karl like I had hoped it would.
--
Bill "win some, lose some" Asher
> In fact, if one were to be so crude as to cook the roast in a
> (heaven forbid!!!) microwave oven, the entire scenario and
> resultant analysis is modified completely.
Well, I was mulling over the following suggestion for Joell, given
that he likes lots of rare meat, and what with him living in a
frigid Swift Current at this time of year and all:
Pop the (fresh) roast in the microwave set on defrost cycle timed
for half the weight of the roast. This should produce a slightly
warmed, rare roast which is what he wants. However, the
appearance would be singularly unappetizing.
So, you go to your tool storage locker and grab one of those
toilet auger thingies, and turn the spiralled business-end of the
auger into an end of the roast. (Choose any part of the surface
if the roast is spherical thus without a defined end, or one of
the two ends if the roast is log-ical.)
Grab the roast-on-auger assembly, and go smartly to the
neighbourhood minor hockey arena (a curling rink is an adequate
substitute). Extend the roast up very close to one of those
ceiling-mounted, gas-fired radiant heaters they use to keep
parents' noses and foreheads warm, and turn the auger rapidly so
that the exterior of the roast is quickly but uniformly seared to
an appealing dark crispness.
That should produce a nicely done, appetizingly appealing roast -
with the most of the meat warm and succulently rare.
Why go out when you can do this at home. Holding the roast over the
Bernz O'Matic Home Gas Welding Torch with the flame spreader attachment
installed on the nozzle with two two-pronged meat forks (the kind with
long handles and long tines) should work just fine. After that, he can
set the roast down on its serving plate and use the torch to quickly
carbonize the sugar glaze on the dessert pudding.
C "you have to think of it as a process" L
> I have a question I'm hoping one of you scientist gastronomists can
> help me with.
> I have this 6.2 kilo carp. (Don't ask me where i got it, let's just
> pretend it's a carp, not a cigarette-butt-eating koi from the
> Emperor's private moat, wouldn't want anyone getting into trouble
> here.) The recipe suggests I nail it to a pine board using iron nails
> and bake in a medium oven 1 hour per kilo or until the fish is easily
> scraped into the garbage. Serve the board with fresh lemon slices and
> a piquant onion relish.
> While the recipe is quite specific on types of nails (no treated,
> galvanized or stainless steel) and cooking times, it is lacking in one
> important aspect (what we used to call 'jello').
> How big a pine board to use?
Ahhh ... tradition ... it's always a challenge to do things the correct
way, isn't it?
I asked my wife and she looked at one of her grandmother's Japanese
cooking scrolls. It says there that you're supposed to use a board of
sugi (cedar) or keyaki (zelkova) for carp, but only if the zelkova is
freshly cut down. Pine is for burning trout and anchovies. If you
don't have a spare cedar board around, you can always hack grandma's
cedar chest to pieces and use a board from that. You can roll the
prepared fish in the lavender from the sachets after you've tied it
closed for extra flavor.
The board should stick out from under the carp at least one cm. (or two
/tai/ in the old measurement system) in all directions, after you've
gutted it and filled it's belly with sea salt and red umeboshi (pickled
plums). So there's your board size question answered. Oh, and after
you've stuffed the fish, you have to tie it closed in the Tohoku kimono
wrapping pattern using a string made of braided strips of yellow bean
vine. THEN you nail it down to the board using a hammer with a hand
forged head.
The nails should be pure iron, hand forged ones from one of the better
nail smiths in Kyoto or Omi-kuni. And no lemon. You always serve the
board with yuzu juice and a bottle of an impertinent little dry nihonshu
from Aki-kuni or Kikkawa-kuni.
HTH.
CL
> So, you go to your tool storage locker and grab one of those
> toilet auger thingies,
Especially appropriate for those used roasts Peter buys.
--
Steve
> a cooking conundrum
Is that like one of those Reynolds roaster bags, but smaller?
--
Steve
I didn't realize I'd stumbled onto one of those "guy" threads.
Now where did Robb go? He usually thrives in this environment.
--
-- DE
While Karl's attention is elsewhere, God is keeping the discussion under
observation ...
--
Peter
> Peter McCormack wrote:
>> On Thu, 15 Dec 2005 11:40:22 -0500, Peter wrote:
>>
>>>The cooking instructions for a roast say 20 min to a pound. The roast weighs 6
>>>lbs, meaning cook for 2 hours. If I cut the roast in half I will get two 3 lb
>>>roasts, each as thick as the original. Alternatively, if I cut 1/3 of the roast
>>>off, I will of course have 1 4lb roast and one weighing 2lbs. All roasts have
>>>the same thickness. It doesn't make sense to me that each roast should cook for
>>>a different time. What am I missing?
>>
>> You're missing an assumption about the average size and shape of a roast.
>> What really counts os the thickness or, more meaningfully, the depth to the
>> centre, of the meat. Because of the limitation imposed by the size of
>> domestic ovens (and therefore a certain conformity in the sizes of pieces
>> of meat that can be cooked in them), the weight/time equation works well
>> enough most of the time.
>>
> I don't fully agree.
>
> A roast cooks from all surfaces inward; cut one in half, and you have
> two surfaces that are now closer to the center, even if the other two
> are not, so the cooking time does get adjusted as a result.
>
> Also, no cooking instructions ever say to cook a certain time and leave
> it at that; they all have tests for doneness.
True, but with all the other variables (and any adjustments after doneness
tests), the authors of the weight/time instructions usually get away with
it, even if the cook doesn't. Added to that, ovens vary, and are variable -
even after three years, we still haven't figured out reliable
time/tremperature offsets for our fan oven. As a couple of others have
suggested, a meat thermometer is the way to go.
--
Peter
> new verb for the a.c. FAQ: karl (vt): to deliberately bait someone using
> snide innuendo of an explicitly sexual, racial, or intellectual nature.
> e.g. 1. Bill was karling Debra over her lack of prowess in the kitchen
> and klingonesque sexual appetites.
>
> (do I get bonus points for karling Debra in my definition of karling?)
Yes, and a nomination to BOAC.
Let's start using this "You've been karled" thing, now.
--
Giuseppe "Oblomov" Bilotta
"I'm never quite so stupid
as when I'm being smart" --Linus van Pelt
> rare meat
Like tibbogs?
--
Giuseppe "I *know* it's about the amount of cooking" Bilotta
[W]hat country can preserve its liberties, if its rulers are not
warned from time to time that [the] people preserve the spirit of
resistance? Let them take arms...The tree of liberty must be
refreshed from time to time, with the blood of patriots and
tyrants.
-- Thomas Jefferson, letter to Col. William S. Smith, 1787
> Sometimes, just to hear the applied mathematicians snap their pencils in
> anger, I will "solve" a simple differential equation of the form
>
> dX/dt = aX(t)
>
> by dividing through by X(t), multiplying through by dt, and then
> integrating.
Be glad I was too tired yesterday night when I first read this post.
--
Giuseppe "Oblomov" Bilotta
Hic manebimus optime
> While Karl's attention is elsewhere, God is keeping the discussion under
> observation ...
Now *that's* something I would prefer over having to use the W key on
my keyboard ...
--
Giuseppe "Oblomov" Bilotta
Axiom I of the Giuseppe Bilotta
theory of IT:
Anything is better than MS
Uh, Peter, did I not just say "they all have tests for doneness"? Just
what would you consider a meat thermometer, if not a test for doneness
that is checking the internal temperature of the meat?
-- DE, feeling Toppish this morning
<sheepish>Yes Miss.</sheepish>
--
Peter
> On 15 Dec 2005 23:53:57 GMT, William Asher wrote:
>
>> Sometimes, just to hear the applied mathematicians snap their pencils
>> in anger, I will "solve" a simple differential equation of the form
>>
>> dX/dt = aX(t)
>>
>> by dividing through by X(t), multiplying through by dt, and then
>> integrating.
>
> Be glad I was too tired yesterday night when I first read this post.
>
I was like 0 for 40 yesterday in trolling. It was like I was Dan Akroyd in
that skit on SNL a long time ago where he is the radio talk show host and
can't get anyone to call in so he starts saying more and more ourageous
things, ending with: "How about killing baby puppies? I'm for it."
--
Bill "new day dawning" Asher
We must get Wim back here to show you all how it is properly done!
(But it was a very nice effort, Peter, and left me in a generous mood
today.)
-- DE
LOL!
> Had to expand any doorways recently? You know how these scientist types are!
Are you asking if she gained weight?
--
Peter
>
> -- DE, feeling Toppish this morning
Reverse missionary?
Thought you had more imagination than that
--
Peter
Of course not!
I was inquiring as to Bill's hat size!
--
-- DE
<snip>
>
> Of course not!
>
> I was inquiring as to Bill's hat size!
>
I have a really small head, just so you know. My bicycle helmet size is
xxs and I typically have to special order them.
--
Bill "not a swell guy" Asher
All the humo(u)r in it has been lost now, though, *sigh*.
Mind if I troll you instead, Mr. <no, I won't say it!>
-- DE
>Peter wrote:
>
>
>
>>"Rectagon" <rect...@netscape.net> wrote in message
>>news:11q3clm...@corp.supernews.com...
>>
>>
>>>Peter wrote:
>>>
>>>
>>>
>>>>But, each of these cuts have the same depth to the center. The
>>>>only significant variant is the length.
>>>>
>>>>
>>>>
>>>But you won't end up with the reddish centre part which is
>>>crucial to a good roast!
>>>
>>>
>>>
>>???
>>
>>
>>
>
>Cut to the chase. Get a meat thermometer.
>
>
A good one, if you cook like I do, it makes all the difference,
particularly with roasts. But then, I like chuck roasts for the
delicious fat it has.
Sometimes a hat is just a hat.
--
Bill "having a bad hair day" Asher
Of course a good meat thermometer is a necessity. The particular roast in
question was prime eye round, which is plenty juicy. I personally think chuck is
too to chewy to make a good roast. Many cheap buffets pass of chuck as roast
beef.
--
Peter
> I have a really small head, just so you know. My bicycle helmet size is
> xxs and I typically have to special order them.
That's the Beldar Jr. model?
--
Steve
It's not so much the size as the horns.
--
Bill "devil in the details" Asher
Oh goody, approval! Can I be naughty now?
--
Peter
Hmmm, and here I thought that was what got us into this in the first
place! <wg>
The question is: have you been naughty enough to be pleasing?
Or are you especially pleasing when you are naughty?
-- DE
(figuring that Santa has got it all wrong)
Whatever. Too many foreign pop culture to make any sense of it, for
me.
--
Giuseppe "Oblomov" Bilotta
"I weep for our generation" -- Charlie Brown