[conspire] sous vide question.

[Ivan Sergio Borgonovo]

On 10/24/2017 06:40 PM, Paul Zander wrote:
> If I understand, the key feature of sous vide is temperature control.
> In traditional cooking methods, there is a very broad range of
> temperatures between “hot” and boiling.  Boiling is easy to observe,
> so most recipes say simmer or boil.
> 
> It is rather easy to find an oven thermometer or a candy thermometer
> in the cookware department.  Thermometers for simmering are not
> marketed (except for the chem lab.)

As said you don't need very precise temperature control unless you're 
planning something really "chemistry" oriented. Precision of 1C should 
be enough. You could even think to do something more sophisticated and 
provide programs (1h at 70C, 4h at 55C).

You can buy a temperature sensor for less than 1$, glue it to the 
outside of the internal layer of the pot and measure water temperature 
indirectly.

I assume the pot is something like


|----|       |----|
|    |       |    |
|    |       |S]  |
|    |_______|    |
|    /\/\/\/\     |
\_______R_________/

Consider that the content will spend most time in thermal equilibrium 
and that should be enough to measure the temperature of the water 
indirectly without using an immersion sensor... you'll just have to 
calibrate the sensor.

> Food science has proven that protein (meat) shrinks as it is heated.
> This drives out water and causes the food to be tough and dry.  The
> higher the temperature, the more shrinkage.  Boiling is much too hot
> for meat and most vegetables.

Yep... that's why having a meat with different tissues you may consider 
adding program cycles. Temperature are generally below 70C.

> Having had occasion to design other temperature controllers,
> including one with the set point at 60K, I am reasonably confident I
> can get the electronics correct.  Also use a thermometer to verify
> the calibration.

If you're doing something analog.. consider you'll have to deal with 
thermal inertia and a bit of non linearity because you're going to 
measure temperature indirectly, unless you want to buy an immersion 
sensor, but then you'll have to make a hole in the pot etc...

> I will have to think about water circulation, the shape of the pot,
> and how the bag(s) might hinder flow.

Water circulation is going to raise the cost of everything pretty much 
and it may not be that useful depending on the size of the pot etc...
At that point you'd better start from scratch.

> From the various samples by Ross, I think the real advantage of sous
> vide is with tougher cuts like brisket and ribs. Over temperature
> shrinks proteins and makes meat tough.  Long cooking time breaks down
> connective tissue and makes them tender.  Sous vide can balance the
> two conflicting requirements.

Unfortunately connective tissue and proteins degrade at different 
temperatures generally connective tissue at higher temperature, so 
mostly you're just making a better compromise.

Cooking in a pan has higher temperatures but you generally you won't 
have enough time to heat the internal part unless you "overcook" the 
outside part.

Furthermore some chemical reactions that give food flavour happens at 
even higher temperature.

So most of the time you do both... sous vide + pan, to just heat the 
surface.

> I am amused by some web postings to sous vide fish fillets.  I can
> saute fish in 10-15 minutes in a frying pan.  Looks like a solution
> in search of a new problem.

Fish cook at much lower temperature and doesn't have connective tissues 
that require softening, generally it is rich of water that is a good 
conductor, fish meat don't get as hard as meat if overcooked.
I haven't been able to find any good application for sous vide and fish.

But maybe there are.

Cooking vegetables with sous vide on the other side could be very 
interesting.

> Rick has a good point about temperature and safety.  There appears to
> be a risky region with some recommending cooking rare steaks at 125F
> and other saying 140F is the minimum needed needed to be safe.

You can kill most things at 60C after 5min. There are some recipes that 
go below 55C and average times are far longer that 5min.
I wouldn't be concerned about that, rather I'd be concerned about the 
result since different cut of meat and different recipes may need 
different temperature with a higher precision that 5C.
Plus most seasoning and spices have a disinfectant effect.

have fun hacking

-- 
Ivan Sergio Borgonovo
http://www.webthatworks.it http://www.borgonovo.net