Reheating sous vide and saving time.

[realoldnick]

Are there any data about how long it takes food from the fridge to heat to a percentage of the applied temperature in the bath?

So far as I have seen, to reheat sous vice food sous vide, you set the bath temp to what you cooked at, so as to not overcook, and then use the original time, sans tenderising and pasteurisation, for a simple warming to bath heat.

It occurred to me that nearly all meat is acceptable to eat at a temperature quite a bit lower than the actual cook temp: it just needs to be warm to bring out the juices and wake up the meat. It would save a bit of time (possibly quite a bit, because the temp delta speed is anti-log or like that...asymptotic) if you used the original temp to heat the food, but were happy to settle for a lower serving temp.

So it seems to me of use if you could know a time at which the food reaches some percentage of the bath temp, because it seems that the time to _reach_ bath temp is not much affected by the bath temp, just by thickness....that makes sense to me; higher "temperature pressure", faster temp climb. But I can't find anything about this, graph or figures.

So, for example. I cook at 57 C, for however long I need to get the desired effect. I then refrigerate. Later I want to heat for eating. Say I am happy to eat at 40 C. In a 57 C bath, given a thickness, how long would it take?

Any info greatly appreciated.

Nick

 

[daveomak]

Baldwin explains everything about sous vide cooking....

http://www.douglasbaldwin.com/sous-vide.html

 

[dr k]

This is the heating table from the link above that Dave posted. If you want to reheat in a water bath at 57*C and pull at 40*C, 40/57=.7 so 70% of the time on the thickness/shape time below maybe a starting point before sticking a therm in the meat.
Heating Time from 41°F (5°C) to 1°F (0.5°C) Less Than the Water Bath’s Temperature
Thickness Slab-like Cylinder-like Sphere-like
5 mm 5 min 5 min 4 min
10 mm 19 min 11 min 8 min
15 mm 35 min 18 min 13 min
20 mm 50 min 30 min 20 min
25 mm 1¼ hr 40 min 25 min
30 mm 1½ hr 50 min 35 min
35 mm 2 hr 1 hr 45 min
40 mm 2½ hr 1¼ hr 55 min
45 mm 3 hr 1½ hr 1¼ hr
50 mm 3½ hr 2 hr 1½ hr
55 mm 4 hr 2¼ hr 1½ hr
60 mm 4¾ hr 2½ hr 2 hr
65 mm 5½ hr 3 hr 2¼ hr
70 mm — 3½ hr 2½ hr
75 mm — 3¾ hr 2¾ hr
80 mm — 4¼ hr 3 hr
85 mm — 4¾ hr 3½ hr
90 mm — 5¼ hr 3¾ hr
95 mm — 6 hr 4¼ hr
100 mm — — 4¾ hr
105 mm — — 5 hr
110 mm — — 5½ hr
115 mm — — 6 hr
Table 2.2: Approximate heating times for thawed meat to 1°F (0.5°C) less than the water bath’s temperature. You can decrease the time by about 13% if you only want to heat the meat to within 2°F (1°C) of the water bath’s temperature. Do not use these times to compute pasteurization times: use the pasteurization tables below. (My calculations assume that the water bath’s temperature is between 110°F (45°C) and 175°F (80°C). I use a typical thermal diffusivity of 1.4×10-7 m2/s and surface heat transfer coefficient of 95 W/m2-K.) For thicker cuts and warmer water baths, heating time may (counter-intuitively) be longer than pasteurization time.70

 

[daveomak]

If you want to reheat in a water bath at 57*C and pull at 40*C, 40/57=.7 so 70% of the time on the thickness/shape time below maybe a starting point before sticking a therm in the meat.

Kurt, morning... How did you calculate those numbers .. Are they scientifically correct ??

 

[dr k]

If you want to reheat in a water bath at 57*C and pull at 40*C, 40/57=.7 so 70% of the time on the thickness/shape time below maybe a starting point before sticking a therm in the meat.

Kurt, morning... How did you calculate those numbers .. Are they scientifically correct ??

That's why I put the disclaimer at the bottom because this is a sou vide heating/reheating chart and not the pasteurization chart. It is my understanding that his food has been pasteurized at 57*C and quickly cooled in an ice water bath in the fridge so it can last up to 4 weeks in the fridge. Now he wants to reheat in a 57*C water bath for a higher temp pressure for quickness and wants to eat it at 40*C. Baldwin stated that heating not pasteurizing to your desired doneness and searing to finish should not be for lowered immune system people and should be consumed within four hours but this food has been pasteurized and just needs to be heated to 40*C. The best way is to have a sou vide probe in the meat in a 57*C water bath and pull and eat at 40*C. If no probe is in the meat, I just took a fraction of the time to start checking the temp. If it were me, I'd probably put it out on the counter and consume it within a couple hours just to take the chill off. In the chart above a 35mm 5*C (fridge temp) slab like steak takes 2 hours to heat to .5*C below the water bath temp. I just took 70% of 2 hours so I'd check for 40*C temp in 1.4 hours or before. I follow the pasteurization chart times on initial sou vide cooks if not longer because it can't over cook or change texture under 48 hours.

 

[daveomak]

Later I want to heat for eating. Say I am happy to eat at 40 C. In a 57 C bath, given a thickness, how long would it take?

This chart is for heating foods ONLY...

If you have a 1" / 25mm steak, why not use Baldwins chart ??? No need to worry about the final temp... Your sous vide handles that... If your food has been perfectly cooked, why increase the bath temperature that may overcook it....
..................slab.......cylinder........sphere....SHAPES...
25 mm.... 1¼ hr..... 40 min....... 25 min
Approximate heating times for thawed meat to 1°F (0.5°C) less than the water bath’s temperature. You can decrease the time by about 13% if you only want to heat the meat to within 2°F (1°C) of the water bath’s temperature..

 

[SmokinAl]

Well I haven't really got into all the scientific stuff, but I reheat all kinds of meat. PP, brisket, fatties, pastrami, corned beef, eye of round, etc. You get the picture. I take the meat out of the freezer & set the SV at 143. I usually let it heat for 1 to 1 1/2 hours at that temp.It doesn't cook the meat any more, but warms it up nicely. If you have frozen some AuJus in the bag it makes it even better.
Al

 

[dr k]

Well I haven't really got into all the scientific stuff, but I reheat all kinds of meat. PP, brisket, fatties, pastrami, corned beef, eye of round, etc. You get the picture. I take the meat out of the freezer & set the SV at 143. I usually let it heat for 1 to 1 1/2 hours at that temp.It doesn't cook the meat any more, but warms it up nicely. If you have frozen some AuJus in the bag it makes it even better.
Al

Right especially from frozen to reheat. In this case fridge temp food if it was a steak like I mentioned above, I wouldn't be thinking too much about it. Run faucet water warm to the touch and fill a pan and put the sealed bag in it for.5-1hour. He just wants it to 104*F, 40*C.

 

[realoldnick]

Thanks for all the replies.

Trouble with Baldwin is the attached :)

It's his formula for heating times and rates. :eek:

I am up with pretty much all of what is said and I have all the _full_ heat times (to 0.5 deg c below the bath etc). I am looking to minimise and plan the time of reheat. Say I come home in the evening and want to reheat a steak as fast as possible asndf haver an idea of when it will be ready. That is why I was looking for something that predicted the time.

I use a meat thermo for this, but that does not plan the time, just measures it.

The only graph I found was for mahi mahi, IIRC 27mm thick. It also seems that most merat is within quite a small range of thermal conduction. So I figure I cam assume meat is much the same and apply the "square of the thickness" law of heating to at least get an idea, then use a meat thermo to measure. If I come outg ahead on time then all the better.

 

[realoldnick]

This is the heating table from the link above that Dave posted. If you want to reheat in a water bath at 57*C and pull at 40*C, 40/57=.7 so 70% of the time on the thickness/shape time below maybe a starting point before sticking a therm in the meat.

Actually the curve is way not linear, so using 70% will result in an overestimate of the time it takes. From the mahi mahi chart by Baldwin, 40C is reached in 12 mins. To get to the water bath temp takes 30 mins if I read it right.

I reckon that while the heat speed is faster for fish than meat, that _curve_ will apply to either: it's about temp pressure rather than materials. So I just use the reach bath temp times for meat of thickness then apply that curve.

 

[realoldnick]

I used that curve above, with (again)the idea that the _curve_ is going to be similar for meat and fish. From that I have made a few figures for required eating temperature when placed in a bath temperature. I am going to test them out, which will of course take a lot of measuring and time :(.

With all sous vide, my worry has been time, if I try to get someone else with a busy schedule to use it (and I have someone in my family who wants to learn). So I would encourage sous vide-freeze-reheat for a faster "cook" after work another day . But that means a time budget, so I want to get a good idea of what happens. I know BBQ-ers are much more "wing it and watch" than sous vide guys, but you are the only forum who has really tried to help and I thank ou for that.