Your bags seem to float horizontally, which makes temperature uniformity and heat transmission in an unstirred bath even worse. You might try to suspend your bags on a skewer (see http://forums.egulle...ost__p__1699134 ) and eventually clamp a table cloth weight (this idea is from Bob Jueneman) to the bottom rim of the bag:
--- snip --- snip --- snip ---
A few days ago I cooked a rolled prime rib of beef for 24 hours at 55C. Seared with a blow torch first. Then cut down the middle and then the two steaks were seared in a hot griddle afterwards. This was inspired by Heston Blumenthal's perfect steak. I chose to do it at 55C after reading so much about potential bacteria growth etc. The meat was a perfect medium-rare. However next time, I will do it at the same temperature as Heston which is 50C. The flavour and texture was really nice. I finished it off with some melted smoked butter, and sprinkle of smoked salt.
Comment by PedroG: 24h / 50°C is definitely dangerous. You might try 53°C if you can keep your bath stable at 53°C ± 0.1°C controlled by a NIST- or ISO-calibrated high precision thermometer. With an unstirred bath and without a calibrated reference thermometer you should rather stay at 55°C.
Covering the bath with ping-pong-balls reduces heat loss and water evaporation, and a simple indoor fountain pump (mine supported 59°C without problem) may substantially enhance water circulation and temperature uniformity, see http://forums.egulle...ost__p__1729644
Thank you for your advice and suggestions. The bath is unstirred but has heating elements on three sides and the bottom, and is double insulated (two layers . It also has a lid (which I didnt photograph) which fits nicely on top and prevents much of the temperature fluctuation. The bath is pretty good at holding a steady temperature (albeit according to its thermometer in unstirred water, but apparently the design of the heaters is such that it promotes convection currents).
To quote it's manual "The Tank of the bath is made of seamless corrosion resistant stainless steel for a longer life time and easy cleaning. By means of the smooth surfaces of the tank, the risk of contamination is minimised. The sheet heaters are placed on 3 sides outside of the tank, the use of a PID control system and triple insulation consisting of glasswool, an aluminum layer layer and an air gap, gives this water bath an excellent temperature uniformity and stability."
It is also stated to have:
Tank Volume, liters 9.5
Useful Volume, liters 7
Temperature Range Ambient Temperature +5ºC / 99.9ºC
Temperature Sensor Fe-Const
Control System Programmable PID Microprocessor
Temperature Set and Display Sensitivity 0.1 ºC
Temperature Uniformity <40ºC ±0.2ºC
Temperature Stability ±0.1ºC
Timer 99.9 hours + Hold position
Delayed Start Timer 1 min. to 99.9 hours
Internal Material 304 Stainless Steel
External Material Epoxy-Polyester Powder Coated Steel
Power Supply 230V, 50/60 Hz
Power Consumption 800 W
Internal Dimensions (WxDXH) mm 240x300x150
ALTHOUGH IT ONLY ALLOWS ME TO COOK UP TO 80C!
I agree with the floating issue, however that photo was of the beef, which wasnt actually floating, its just horizontal coz thats the only way it would fit in. The bath is more shallow than I would like. As I am currently using ziploc bags, i do try immersing them in cold water first to help get rid of the air inside and then sealing, but there is still always some. I have tried a skewer through the top above the seal to keep them vertical, which does help.
I was quite annoyed that there was a really cheap chamber vacuum machine for sale on ebay today, but I missed it due to my gf hassling me!!! So I have been considering getting this Food Saver. What are your thoughts please?Food Saver V2860
Once again I really appreciate your feedback!
Edited by Guy MovingOn, 23 February 2010 - 09:47 PM.