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Modernist and Baldwin Slab Charts -- Sous Vide


sigma

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So, I'm looking at the two charts, and Baldwin seems to suggest that which is intuitive to me. That is to say that cooking a meat in slab form should take longer than in cylinder form for each thickness of meat. On the other hand, Modernist seems to suggest that, for all but the largest sizes, cylinders should take more time. This makes no sense at all. In fact, Modernist estimates that a 15 cm diameter cylinder of 3 cm thickness would take 1:21 to cook to 55 degrees, while a slab of at least 5x length and width of the same thickness would take approx 50 minutes. But this makes no sense because the slab is at least 15x15 cm, by definition, and in that case you could inscribe the cylinder in the slab. But by doing this, by cutting off the meat and making it smaller, without changing thickness, you would increase the cooking time! That seems impossible. I am sure I am reading the whole thing incorrectly, but I would really appreciate an answer from somebody else who has puzzled over the same issue. Thanks!

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Tables 1 and 4. Table one assumes a diameter of 15 cm. Table two assumes of 15 cm but infinite diameters. It isn't operative for this question, though, since slab and fixed diameter both deal with increasing thicknesses.

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  • 3 weeks later...

Sigma--I'll take a gander, but I don't have a copy of MC, and I find your description of the various dimensions a little hard to parse. Can you post a visual aide with the dimensions labeled (either a scan of the MC page or one you draw yourself)?

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I can try, though it really isn't my strongsuit...

So, here is the cylinder chart from Modernist which assumes a 15 cm diameter. Choosing a thickness of 3 cm, the diameter is 5x the thickness. Choosing a delta T of 55, we get 1hr 21m.

dsc0039qx.jpg

Here is the slab chart from modernist. It assumes a length and width at least 5x the thickness, so once again we choose 3 cm thickness, and we have a slab that is no smaller than 15x15x3, given the book description. Once again we choose a delta T of 55, and the time, according to the book is 49 min 45 sec.

dsc0041di.jpg

Since we have chosen the smallest possible size for the slab (it must be at least 5x length and width) the logic here should hold no for all possibilities. Now, since the cylinder from chart one can be inscribed in the slab from chart two, it is clearly smaller in some way. However, the time suggested is longer. In fact, the book suggests that by increasing the size of the cylinder to make it a slab, in other words by filling in the area left by the inscription, we can lower our cooking time by 26 minutes. This seems absurd, so either I am reading the charts incorrectly, or there is something very wrong with their model. Given that nathanm et al are clearly brighter than I am, I would assume the former, but Baldwin's chart, which you can see on his site, conforms to my theory.

I'd love an explanation from the Modernist people, or from anybody else, or a critique of my argument. Also, sorry if there is a copyright issue, I couldn't figure another way to do this.

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Looks like the approximations crossover when the thickness is between 5cm and 6cm--all the 5cm times are shorter for the slab, and all the 6cm times are shorter for the cylinder. I'd say the slab times are all probably "correct," and the MC model is broken for thin cylinders. I too would be interested in how the MC team came up with such wonky numbers for thin cylinders.

Another oddity: take a look at the cylinder times for a delta of 65F. If you look at how much additional time is required per additional centimeter of meat you get this:

3cm --> 4cm: 41min

4cm --> 5cm: 44min

5cm --> 6cm: 35min

Huh? At the very least, those numbers should be monotonically increasing or decreasing. There's something seriously wrong with that table.

Edited by emannths (log)
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  • 2 weeks later...

I wonder if they got the terms screwed up in the cylinder table.

It doesn't make much sense to me to have a cylinder of a constant diameter, but varying thickness -- that's just a round slab.

If however, the captions were reversed, and they were talking about a cylinder with a fixed 15cm/6 inch LENGTH, and variable DIAMETER, that would make a whole lot more sense!

I know that the errata says that the 6cm column for all three pages of tables are wrong, but I don't recall seeing anything else.

Nathan?

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I should have gone back to the book, rather than just looking at sigma's copy. Table 1 is for a cylinder of a fixed diameter but varying thickness (a round slab, in other words), while Table 2 is for something like a sausage of fixed length but different diameters. (That is the only "cylinder" table that makes any sense to me.)

But comparing the times for a round slab that is 5 times the thickness, vs. a square slab that is 5 times the thickness in both directions, the times ought be approximately the same, or the round slab should take less time, so something is clearly screwed up.

The errata for the 6cm column for Table 1 shows 3 h 32min for a 65C delta T. That would be 43 minutes for the 5cm to 6cm difference, as opposed to 35 minutes. Compared to the 44 minutes for the 4cm to 5 cm, that's at least in the ball park. But you are right -- someone ought to rerun the calculations again, and explain their assumptions. That ways, someone like Douglas Baldwin could rerun them as well. Right now, we have apples and oranges.

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