July 20, 2018 at 2:34 pm #885612fergusmomParticipant
Hello – newbie here! I’m using an InstantPot Ultra.
I’m assuming the times listed on the meat sections of your chart are ‘per pound’, is that correct?
If so, I’m confused about how long to cook my 5.5 lb boneless lamb leg. In the “by thickness” section, it says “12/high/natural” for lamb in general, and in the “by cut” section, it says “35/high/natural” specifically for “lamb leg/shank”. In both cases, I’m looking at the InstantPot (not mini) column.
How long should I set my InstantPot for to cook this lovely roast for dinner tonight?
Thank you!July 21, 2018 at 1:34 am #885622GregParticipant
The “By thickness” section is “per inch” thickness. The “By cut” section is for the leg. It assumes an average size of three inches thick.
So either cook it for 35 minutes as per the by cut section, or plop it on a table and use a ruler to measure how high it rises. Then use the per inch section to calculate the cooking time.
In general, what determines how long a given item takes to cook is it’s thickness. NOT its weight. This is regardless of the cooking method. The weight of an item is analogous to its thickness, but it doesn’t always work. Thickness always does.
Think about it. Take two equal weight pieces of fillet steak. Hammer one out to 6mm (0.25″). Put them both on a hot griddle at the same time. You would not expect the flattened out one to take the same time to cook as the chunky one would you? Likewise a spatchcocked chicken cooks much faster than the same bird would if left whole and stuffed.
The use of weight to determine cooking time is a holdover from the time when cooks were uneducated. They were told how much it weighed when they bought the piece. They were not told how thick it was.
The science behind it is pretty straightforward. For a given substance at a fixed pressure and temperature, heat travels through the object at a fixed rate. It is considered cooked when the centre reaches a given temperature. If you change the temperature (an oven) you will change the time it takes to cook. If you change the pressure (pressure cooker) you will change the time it takes to cook. If you change the thickness (mallet) you will change the time it takes to cook. If you change the desired final temperature (Rare Vs “Well Done”) you change the time it takes to cook.July 21, 2018 at 2:07 am #885624GregParticipant
I just re-read your post and noticed the 35mi for a shank.
Shanks are a special case. They are hardworking parts of the animal and have a lot of connective tissue (gristle, Tendons etc). they need extra time to break this down into tender and flavourful gelatin. What I said above still holds. It is just that connective tissue is a different substance to meat.
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