I have gone through 2 Taylor digital thermometers with probes and ruined a couple of batches of cheese because of inaccurate readings. What thermometer do you all recommend? I really liked the probe feature but maybe that's not an option and still be reliable.
I like analog thermometers that can be calibrated with the nut at the top. The small ones are really cheap, maybe $4. I calibrate them a few times a year and new ones before use. I am not a fan of digital ones; too much money spent over the years on new probes and broken thermometers. Same for hydrometers; I prefer analog ones.
Well there you go. Last night I reached for the old analog one in the drawer so I could keep making cheese. Darn!
I used to use a probe type when smoking my bacon; right up until the time it started reading 15 degrees too low. I now use the analog thermometers with the nut at the top for calibrating, and calibrate them each time before using. I liked the probe, but there was no way to calibrate it, and now I just don't trust them.
Yeah. I got about 3 uses out of them and then I could tell the temperature more accurately with my finger than what the thermometer read.
I'm sort of anal about temperature and like to be within 1 degree of desired temperature targets. I just can't read an analog accurately enough to get this close and on several occasions I have twisted the analog dial while it is on the pot and wiped out the calibration. So, I prefer a digital without an external plug in probe. Here's what I use.
Digital Thermometer (http://cgi.ebay.com/Digital-Kitchen-Thermometer-/160494198152?pt=LH_DefaultDomain_0&hash=item255e331d88)
I occasionally test it in both frozen slush and boiling water to be sure it is "calibrated".
Can the CT-03 be calibrated?
I actually got that very thermometer (see photo below). I use it in my 20qt pot for Sous Vide cooking and for some cheese. (How I wish that the temp. alarm be adjustable to low sous vide / cheese temps)
My problem is that like many others here, I don't know what thermometer to believe anymore...
Analog thermometers should be the most accurate and reliable (even Extech tells you to calibrate their probe thermometers based in an analog thermometer). That said, analog thermometers too have been plagued by inconsistent readings from one brand to another.
My assumption (for now) is that the most accurate readings are with analog thermometers that carry the NSF seal on them. These are the only ones approved for professional use - for a reason, I suppose.
What's wrong with this picture?
(Note in photo below, how the only thermometers that were in line with each other were the 2-week old digital oil/candy thermometer and the one analog thermometer that carries the NSF seal)
In the digital thermometer world, I only like the durable K/J probes, like the ones cooper atkins makes. But those are pricey.
I also calibrate regular dial thermometers against an alcohol lab thermometer. And I have a correction curve for the lab thermometer based on temp readings at boiling and ice water, corrected for atmospheric pressure. This lets me have a solid known standard that is authoritative.
Linuxboy, I think it takes it over the top for me... just need something dependable and accurate - and not too expensive either. I am thinking that the Taylor brand professional food service thermometers are worth the $17-$25. They are all NSF and ANSI certified, some are ISO and HCAAP 9000 certified too and have accuracy as much as +/- 0.6F all the way from 0F to 230F. They can all be calibrated. Only question is to what - since I don't have a lab thermometer...
I am also planning on building a machine to do both sous vide and cheese. It will be made with industrial grade thermocouple connected to a PID unit that will be programmed to control a heating element based on the milk/water temp. Not sure how to calibrate that thermocouple either... Has anyone here made such thing before? If so - advice will be helpful. If not, does anyone want to share the experiment? The parts should cost about $30-$60 only and it shouldn't take more than an afternoon to build.
Quote from: iratherfly on November 29, 2010, 09:49:55 PM
They can all be calibrated. Only question is to what - since I don't have a lab thermometer...
Couldn't you just use the boiling and freezing points of water in absence of a lab thermometer?
Absolutely, you can use the boiling and freezing points. I like to use lab thermometers to help with calibration because they're cheap ($3) and once you determine the drift curve for that specific thermometer, it always works. It's a do once and re-use kind of approach, to have a single authoritative source. You can do the same thing for thermocouples and figure out the drift, sure. But with cheaper thermocouples, there's room for them to not perform well under all conditions. Like if you drop one and it experiences stress... it could throw off the reliability on cheaper ones. Thermocouples rely on an electrical signal and this can be degraded by physical damage of the cable, circuitry, or junction.
Let me know if that's not clear of if you need help with figuring out how to calculate the bias curve for a thermometer. There's probably some guide you can find online for it, too. I just learned the lab methods long ago, so I still follow the same ones.
Yoav, it shouldn't be too hard to create a PID-controlled unit. There are similar devices out there. One fellow has even created a converted rice cooker to act as an automated cheesemaking machine, like a bread machine.
I use lab thermometers for calibration as well. I was just suggesting the obvious if you do not have one available. My father was a chemist, so I have boxes and boxes of lab equipment and glassware (which comes in handy more often than you would think).
perhaps I don't understand what a lab thermometer is and how it's different from any other high quality thermometer. What is this mystery $3 thermometer that is so good that all those $25 thermometers should go by it? ..and why does it need all these extra recordings? Isn't there just a good reliable instrument out there?
Boiling and freezing points are inaccurate unless you calculate them at ISA (elevation 0 ft MSL and outside temp of 15C) or, you calculate the pressure altitude based on the changes to your air and elevation. Even then, impurities in the water can change their boiling/freezing points. You can use purified water, is the look of bubbles enough of an indication that you should be 100C? How hard should the ice be before you can declare it perfect 0C? In other words, I hope this isn't getting to be as annoying as using pH meters.
An alcohol lab thermometer is analog. And it functions based on the established properties of thermal expansion, which functions linearly based on temperature. Meaning that if you use RO/distilled water, and boil it for the high reading and put in ice water for the low, and record the barometric pressure and elevation (as you said), you can develop an exact bias curve for that specific thermometer. It will have that same bias curve from now on. You might need to make slight adjustments in the future based on the barometer, but those are minor.
It's so good because it's analog.
All thermometers need all the adjustments based on the bias curve of each one. But with calibrateable ones, the bias can be adjusted for. When you use a bi-therm (the metal dial ones), it suffers from the exact same situation as analog mercury/alcohol thermometers - the reading bias. But, unlike the lab thermometer, a bi-therm may develop different bias curves over time, especially as it is calibrated. So it needs to go through the entire effort or recalculating everything to be used as a standard, whereas with a lab thermometer, you just need to adjust for daily differences in the barometer.
With digital probes, they are actually more reliable, especially if of high quality and especially if the circuitry accounts for calibration fluctuations. But same sort of idea if used as a standard - the degree of drift may change, especially if a cord is kinked or it's dropped, or other some such. This rarely happens with good units and easy to spot by using two thermometers to compare.
Yes, there are good, reliable bi-therms, alcohol/mercury thermometers, and digital ones. Most of them are costly.
If I never have to calibrate a thermometer and it's reliable enough for me not to destroy cheese than I may just go for that more expensive one... I seriously doubt that I can calibrate a thermometer based on another thermometer based on a barometer; that's a bit too crazy-laborious. Otherwise, I don't feel that eyeballing frozen water is more accurate than just relying on an NSF/HCAAP certified thermometer, know what I mean?
It's calibration that made me stop almost completely using pH meters and now (I mean, by the time you calibrate them with two liquids and rinse, do the two liquids and the rinse again, clean the probe, stick it in your milk and wait 10 minutes for the a stable number to display - the cheese is doomed. Especially once you acidify the milk to find out it only changed 0.1pH and you can't tell if it's suppose to do this or just a bad pH calibration - unless you have a $1000 food lab meter). I am now looking into getting a no-calibration ISFET meter. Leaving the pH meter behind actually made me a better cheesemaker. I learned to look at the curd, feel it, smell it and judge it based on artisanal methods (such as measuring how much whey is on the curd). Unfortunately I can't say that I am similarly capable of sticking my finger in milk to tell the accurate temp; I am not *that* good. O0
ISFETs still require calibration. They're just easier to clean. And they are still subject to fouling of the junction. The key difference is that there's no glass bulb. I use an ISFET probe, and you're right, the setup would be over 1,000 new. But, I like good instrumentation as an engineer. :)
I agree, a good NSF thermometer shouldn't vary and shouldn't need constant calibration. For me it's no big deal to use a thermometer with known bias curve because I already did the work, so it's now a 30-second task and an additional way to confirm.
What particular brand or model analog thermometer do you happen to have, linuxboy?
Just curious...
The alcohol lab one? It's unmarked, have no clue. I think it came from a surplus sale? Very basic, just red alcohol, annealed glass. it's surprisingly accurate, though.
Quote from: linuxboy on November 30, 2010, 02:15:13 PM
An alcohol lab thermometer is analog. And it functions based on the established properties of thermal expansion, which functions linearly based on temperature. Meaning that if you use RO/distilled water, and boil it for the high reading and put in ice water for the low, and record the barometric pressure and elevation (as you said), you can develop an exact bias curve for that specific thermometer. It will have that same bias curve from now on. You might need to make slight adjustments in the future based on the barometer, but those are minor.
It's so good because it's analog.
All thermometers need all the adjustments based on the bias curve of each one. But with calibrateable ones, the bias can be adjusted for. When you use a bi-therm (the metal dial ones), it suffers from the exact same situation as analog mercury/alcohol thermometers - the reading bias. But, unlike the lab thermometer, a bi-therm may develop different bias curves over time, especially as it is calibrated. So it needs to go through the entire effort or recalculating everything to be used as a standard, whereas with a lab thermometer, you just need to adjust for daily differences in the barometer.
With digital probes, they are actually more reliable, especially if of high quality and especially if the circuitry accounts for calibration fluctuations. But same sort of idea if used as a standard - the degree of drift may change, especially if a cord is kinked or it's dropped, or other some such. This rarely happens with good units and easy to spot by using two thermometers to compare.
Yes, there are good, reliable bi-therms, alcohol/mercury thermometers, and digital ones. Most of them are costly.
Okay, forgive me for needing the further explaining.
So... what based off of the readings we get from it beng in boiling water, the ice water, as well as the recordings for the barometric pressure and elevation, by developing a "bias curve"-- we can now use the readings from this thermometer to compare to all other thermometers and calibrate accordingly?
Is that correct?
If not then I'm not really understanding what functions the "bias curve" serves for?
and, in your last sentence you say that alcohol/mercury thermometers are mostly very costly, but i thought it was the alcohol ones tht you were telling us that cost you only around a couple of bucks?
forgive me for the questions-- I dont mean to be a PITA-- just trying to understand.
Ok, so, for analog thermometers that are not adjustable, they are made according to a standard to read accurately. But, unless you use the thermometer in the exact conditions it was made, it will read differently. And you can't adjust the markings, they are usually right on the glass. So you have to create a chart and manually adjust for your environment in terms of air pressure and in terms of any other bias that comes into play.
That specific bias is unique for your situation. If you calculate it, that analog thermometer should be able to accurately tell you the temp because the bias curve remains the same for that thermometer in your situation. And it then serves as the authoritative source.
Many digital thermometers have a similar version of this idea. In their programs are usually weights that help to automatically recalibrate based on readings.
Notice I said most are costly. It depends on what you need. If you need waterproof, reliable, shock-resistant meters, that will cost. If you want a basic lab one, those are cheap. But the basic lab thermometer is not absolutely foolproof. If you drop it from a high height, it can break (hence, not reliable/durable). Or, the alcohol inside may separate and have air gaps in between (again, during a make, not helpful at all). You can usually fix the latter issue, but still. To have a constantly reliable meter, those usually run $50+. Just because something is NSF doesn't necessarily mean much except the company paid to get it NSF certified. All meters have their drawbacks.
I usually use two bi-therms, calibrated manually and against a lab meter. The bi-therms are durable. I sometimes will glue a bi-therm after calibration to prevent the nut from moving.
I make it more complicated than it has to be. I have a *ahem* fondness for complicated things.
Haha, you sure do Linuxboy!
So now that I understand it better... How often do you think I should check for calibration my good, calibratable NSF analog and digital thermometer? And the probe of my pH meter? (Extech
Also, I am building a Sous Vide and Cheese vat machine. It would be made of a digital PID controller that takes temp readings from a connected high-end food-grade thermocouple (immersed in the liquid) and switch on/off a waterproof heating element (like the one you immerse in a cup of water to boil it for tea) to match a user-requested temperature and keep is steady.
For sous vide sake, the heating element will be in the water and there will be an aquarium type of propeller pump that keep the water circulating to assure even temp throughout the vat. For cheesemaking, I will use a double boiler configuration where the heating element and propeller pump will be in the vat and the thermocouple will be immersed in the milk insert (the double boiler). Hmmm... doesn't this sound like your kind of project? Anyways, how often do you think I should calibrate this thing?
Quotegood, calibratable NSF analog and digital thermometer? And the probe of my pH meter?
Thermometer = every week (or if it's constant, every 1-3 months, as needed, just to be sure)
ph = every make.
if your thermocouple is in a well (no contact with food, does not get gummed up), there shouldn't be a need to calibrate beyond the initial one and an annual/period check to confirm. K/J probes and a good circuit board go a very long way. In the handheld temp meters, it's usually the flexible wire or probe that gets damaged and causes wrong readings. Or a meter falling to the floor, or other shock. Thermocouples are generally reliable if stationary and enclosed/protected.
I can help however you need in terms of design suggestions, but not much time to build one of these myself. I've done PID projects before, but not lately. I've never done power electronics/industrial EE work commercially, but I know the basics. My brother has a master's degree in this (servos, PID, industrial controls, etc), so I could ask for his input, too.
IRF - I deal with a large digitally controlled vat every day. As background, I have a 40 gallon make pot inside a 70 gallon heated water vat. Based on my observations, I have a couple of suggestions for you.
First, I do not feel that a circulation pump of any kind is necessary. I tried this in the water vat and found NO difference in the rate of heat transfer to the milk pot.
Second, the thermocouple should go in the water bath and not the milk side. FarmerJD convinced me of this. You don't need to know what the temperature of the milk is, you want to know where it is going to end up. For example, assume that your milk is 80F and you crank up the heater to warm it up to 90F. The milk gets to 90F and the PID with thermocouple in the milk cuts off the heater. Great, right? No, the water bath had to be much hotter to force the milk to reach an equilibrium of 90F. The water may be 120F and will keep heating your milk. Result? You will end up dumping the 120F water and lose control of the maintenance temperature. Then your milk drops to 86F and you're back to the balancing act. With the thermocouple in the water, you simply set it a couple of degrees higher (because of heat loss) than the desired milk temp and let it do its thing. Right? Well not really. That can take all day to stabilize depending on your volume. So what I do is preheat my water vat WAY higher than finish temp, say 150F. I pour milk into the make pot and then drop the digital controller back to the finished temp +2-3f. The 150F water makes the initial heat transfer MUCH quicker, but the water will stabilized at the finished temp.
Quote from: linuxboy on November 29, 2010, 11:09:58 PM
Let me know if that's not clear of if you need help with figuring out how to calculate the bias curve for a thermometer. There's probably some guide you can find online for it, too. I just learned the lab methods long ago, so I still follow the same ones.
this would be absolutely great if you could post this.
Way better solution than spending $100 on a Thermapen.
Quote from: Sailor Con Queso on December 04, 2010, 10:16:43 PM
So what I do is preheat my water vat WAY higher than finish temp, say 150F. I pour milk into the make pot and then drop the digital controller back to the finished temp +2-3f. The 150F water makes the initial heat transfer MUCH quicker, but the water will stabilized at the finished temp.
This is the fastest way to do it, but make sure you do a little math to make sure you don't overheat it. Sailor has found what his setup needs but your number may not be as high depending on how much water you have compared to your milk.
Quote from: FarmerJD on December 06, 2010, 08:11:44 PM
Quote from: Sailor Con Queso on December 04, 2010, 10:16:43 PM
So what I do is preheat my water vat WAY higher than finish temp, say 150F. I pour milk into the make pot and then drop the digital controller back to the finished temp +2-3f. The 150F water makes the initial heat transfer MUCH quicker, but the water will stabilized at the finished temp.
This is the fastest way to do it, but make sure you do a little math to make sure you don't overheat it. Sailor has found what his setup needs but your number may not be as high depending on how much water you have compared to your milk.
Do you happen to have the math, again, of calculating one's needs, Farmer?
Sorry to bother you.
I would need a little info:
1. amount of water in the boiler/outside container
2. amount of milk
3. final temp of milk desired
4. starting temp of milk
of course the answer would be an estimate since the containers both lose heat to the air.
For you guys that are calculating the thermodynamics, e.g. rate of heat transfer from bath to milk, are you calculating the resulting rise in milk temperature per minute as well? So you don't blow the 2-degrees per minute rule? Here's some other questions:
- Maybe a circulation pump in the bath doesn't help heat transfer to the milk, it should help make sure your controller's heat measurement represents the overall average of the bath's water though, right? I mean, if the water isn't being mixed, won't it have hotter/cooler areas depending on what kind of convection is occurring and where the heating element(s) is/are?
- Would a slow circulation of the milk be a good idea? The reason would be to make sure the pot of milk is heating evenly as well, not hotter towards the outside and cooler towards the inside. No? Plus, if the milk is hotter to the outside, wouldn't the heat transfer slow as well since the rate of transfer depends on the temperature differential across the boundary?
Thanks,
Brian
Quote from: tananaBrian on December 08, 2010, 10:36:48 PM
For you guys that are calculating the thermodynamics, e.g. rate of heat transfer from bath to milk, are you calculating the resulting rise in milk temperature per minute as well? So you don't blow the 2-degrees per minute rule? Here's some other questions:
- Maybe a circulation pump in the bath doesn't help heat transfer to the milk, it should help make sure your controller's heat measurement represents the overall average of the bath's water though, right? I mean, if the water isn't being mixed, won't it have hotter/cooler areas depending on what kind of convection is occurring and where the heating element(s) is/are?
- Would a slow circulation of the milk be a good idea? The reason would be to make sure the pot of milk is heating evenly as well, not hotter towards the outside and cooler towards the inside. No? Plus, if the milk is hotter to the outside, wouldn't the heat transfer slow as well since the rate of transfer depends on the temperature differential across the boundary?
Thanks,
Brian
Good questions. You think alot like I do. These are a few thoughts not meant to be authoritative in any way ;) .
The initial heating phase does not have to follow a slow schedule. The process Sailor described was the initial heating of the milk to 88-90 degrees before adding culture/rennet. With the "cooking" phase, you have to tinker with it a little. I keep my water temp 3-5 degrees ahead of my milk and stop this many degrees ahead of my target. The math on that would be much harder (considering all the variables) than just trial and error for 1-2 makes.
In regards to circulating the water, convection currents will do the trick without a pump, provided the heating element is close to the bottom. See this link (http://www.youtube.com/watch?v=7xWWowXtuvA#) for a demo. Another factor to keep in mind is the stirring of the milk; since it is in constant motion during the heating process (at least mine is), the constant cooling of the water along the milk pot creates another dynamic in the water tank to keep the heat moving by conduction.
On a practical note, this isn't just theory. I have measured my water tank in various places and found no discernible difference even though I have no pump. I actually bought one and wound up not using it because of this.
Hope that all makes sense.
I have developed a spreadsheet to calculate equilibrium temperatures, time to target temp, etc based on my particular setup. Everything depends on volume of water, volume of milk, and the BTU values of your heat source. I have 35 gallons of heated water and 35 gallons of milk in a 70 gallon tank. Since the volumes are the same, quick math is easy for equilibrium temperatures. If the milk starts at 40F and the the water is 140F, then both will reach equilibrium at the average temperature of 90F. Put another way - 40+140=180 divided by 2 = 90F. Of course there is some heat loss, and the heat source keeps generating BTUs so that's why I start with 150F water in my vat. After the water hits 150F, I reset my digital controller to 90F or whatever my target temp is. It is MUCH better to overheat than underheat in the beginning. As the milk heats up, I can always drop the volume of water to slow down heat transfer and avoid overshooting the target temperature. And by the way, these calculations can be used even if you are making cheese in your kitchen sink. You just have to know volumes and temperatures.
Interesting physics and math. Not difficult, but it does take some head scratching. Here are some basic concepts:
It takes one BTU of energy to raise one pound of water, one degree F. Assuming water & milk are both 8.6 lb/gal means 70 gallons (combined water & milk in my vat) x 8.6 = 553 pounds. It will take 602 BTUs to increase that 70 gallons by one degree. Substitute your own volumes to calculate your needs.
By definition, a 1000w (1kw) electric water heating element running for one hour generates 3413 BTUs.
A 1500w element produces 5119 BTUs/hr. So 5119/602 = 8.5 degree rise per hour.
A 4500w would give 25.5 degrees per hour. A 6000w would give 34 degrees per hour.
So now you have everything you need to calculate temperature and times for your own setup.
Hey, If I gave you the spreadsheet, you'd miss out on all of the fun. Enjoy. ;)
Wow. This thread has turned into pure gold. LB, JD, Sailor and everyone else that have contributes so far. Thanks. May the cheese be with you. :)
Quote from: humble_servant7 on December 06, 2010, 07:36:40 PM
Quote from: linuxboy on November 29, 2010, 11:09:58 PM
Let me know if that's not clear of if you need help with figuring out how to calculate the bias curve for a thermometer. There's probably some guide you can find online for it, too. I just learned the lab methods long ago, so I still follow the same ones.
this would be absolutely great if you could post this.
Way better solution than spending $100 on a Thermapen.
Um, a little short on time. But seriously search on google for something like "thermometer calibration curve"
lots of info out there for how to do it.
Sailor, Linuxboy so sorry it took so long to respond to such comprehensive answers. Was away working and haven't had any time to cheese around...
Thanks for your offers to help. A friend of mine is a scientist-professor and said that in his university lab they have these special baths that mimic perfect atmosphere, elevation and pure water. They dump their alcohol thermometers into them to get the perfect universal temperature for calibration. Would love to see that. I am giving him all my thermometers to calibrate. Let's see how this works!
As for your help with my dream machine... Thanks!
The water circulation is not so important when making cheese unless it's a bit of water and a large vat. I just want to avoid hotspots and uneven temps. Milk is usually easy because it's so dense. The pump however is very important for sous vide so it will still be part of the machine. I will just turn it off and on as needed.
As for putting the thermocouple probe in the water Vs. the milk, I am a bit confused as to why. I get that you need the water to be hotter than the milk target but the PID doesn't know how hot is the heating elements and shouldn't care... it needs to start and stop the heating element to assure perfect temp of the milk. In other words, if it takes 137F water to heat the milk to 90F than shouldn't the PID be set to 90F and the thermocouple be in the milk? And what if another day the atmosphere and room temp make it 146F? How would the I (or the PID) know to adjust it? With the thermocouple in the milk the heating elements always switch on/off according to the milk temp; I shouldn't even know the water temp as long as the milk is correct. I have a feeling that I misunderstood a good point. Can you explain?
Quote from: iratherfly on December 21, 2010, 06:12:25 AM
As for putting the thermocouple probe in the water Vs. the milk, I am a bit confused as to why. I get that you need the water to be hotter than the milk target but the PID doesn't know how hot is the heating elements and shouldn't care... it needs to start and stop the heating element to assure perfect temp of the milk. In other words, if it takes 137F water to heat the milk to 90F than shouldn't the PID be set to 90F and the thermocouple be in the milk? And what if another day the atmosphere and room temp make it 146F? How would the I (or the PID) know to adjust it? With the thermocouple in the milk the heating elements always switch on/off according to the milk temp; I shouldn't even know the water temp as long as the milk is correct. I have a feeling that I misunderstood a good point. Can you explain?
The problem is that if the thermocouple is in the milk; and the thermostat is set to 90F; and the water heats to 100F in order for the milk to get to 90F; then when the thermostat cuts off, the final temp will still rise to a point between 90 and 100
without the elements on. I think maybe the confusion was because I tried to tackle two issues at once: the initial heating ( when you are not concerned with the rate of increase) and the actual "cooking" phase when the rate is essential. Or it could be the incredibly long sentences. :o :) Anyway, I hope that makes more sense. Let me know if I muddied the water even more or if I misunderstood the question.
Quote from: iratherfly on November 29, 2010, 09:49:55 PM
I am also planning on building a machine to do both sous vide and cheese. It will be made with industrial grade thermocouple connected to a PID unit that will be programmed to control a heating element based on the milk/water temp. Not sure how to calibrate that thermocouple either... Has anyone here made such thing before? If so - advice will be helpful. If not, does anyone want to share the experiment? The parts should cost about $30-$60 only and it shouldn't take more than an afternoon to build.
Have you had any takers on your sous vide machine experiment? I would start a separate thread for it though. I may just jump in there ....
FarmerJD, I get it. I suppose the only question now is which is better? Putting the thermocouple in the water and Learning at what temp to shut it off in order to get a the correct milk tem? Or, putting it in the milk and learning how long before I reach the desired temp I need to shut it off and time it like that? On the stove, I turn off the heat at 87F to get 90F milk and I feel comfortable and accurate about it... One thing to remember is that water is less dense than milk. It doesn't hold temperature for long time and takes far more energy to heat up than milk, so if for example you have a double boiler configuration where it takes 100F heated water to get your 90F milk. Turning off the heater at 100F will not end up with a milk that's eventually 100F. The milk which is more stable and dense will cool the water down to 93F or so... it becomes the power source of the double boiler now. Does it make sense?
By the way, I always treat the speed of initial heating at the same importance as the cooking phase. In traditional and farmstead cheese the milk comes from the animal and carries the animal's body heat, or sometimes through a pasteurizer with a quick cool down cycle. The keeping of temperature as well as the quick cooling and quick heating of milk are essential in preventing pathogen growth and development of unwanted acids. I always felt that the quicker I bring it back up to desired temp -the higher milk quality I preserve (and I grow less of the competing bacterium).
KosherBaker So far, some very quirky and sweet couple that happen to live a few blocks away found out about my sous vide experiments through Twitter. They have already built a couple of these and they are blogging about it here: http://qandabe.com/ (http://qandabe.com/). We met last Friday and talked food and philosophy in a local coffee shop (got to love this town) and we are building one together in the new year. I am ordering the parts today! I will post photos on a separate thread when we do it. (If you start a thread, I will post it on yours, PM me in case I've missed the thread)
Quote from: iratherfly on December 22, 2010, 05:48:34 PM
FarmerJD, I get it. I suppose the only question now is which is better? Putting the thermocouple in the water and Learning at what temp to shut it off in order to get a the correct milk tem? Or, putting it in the milk and learning how long before I reach the desired temp I need to shut it off and time it like that? On the stove, I turn off the heat at 87F to get 90F milk and I feel comfortable and accurate about it... One thing to remember is that water is less dense than milk. It doesn't hold temperature for long time and takes far more energy to heat up than milk, so if for example you have a double boiler configuration where it takes 100F heated water to get your 90F milk. Turning off the heater at 100F will not end up with a milk that's eventually 100F. The milk which is more stable and dense will cool the water down to 93F or so... it becomes the power source of the double boiler now. Does it make sense?
By the way, I always treat the speed of initial heating at the same importance as the cooking phase. In traditional and farmstead cheese the milk comes from the animal and carries the animal's body heat, or sometimes through a pasteurizer with a quick cool down cycle. The keeping of temperature as well as the quick cooling and quick heating of milk are essential in preventing pathogen growth and development of unwanted acids. I always felt that the quicker I bring it back up to desired temp -the higher milk quality I preserve (and I grow less of the competing bacterium).
IMHO, putting it in the water is better because you are adding heat not taking it away. If you keep the water at 100F, the milk will eventually get there although at an ever decreasing rate and the good news is you don't have to worry about going over. As far as density is concerned the difference is very small especially whole milk like I use with a 4-6% fat value. (1 to 1.03)
I agree about the importance of quick initial heating. My point was that you did not have to worry about keeping it at a slow rate like the cooking phase; you could just heat it as fast as you could. Good discussion, good luck with the sous vide experiment.
Thanks FarmerJD!
My experience using water for sous vide in the same vat usually used for milk -cheesemaking has shown me that the difference is very significant. 2 Gal. milk seem to hold temperature about 3 times longer than ...get this; 4 Gal. water. But it makes me wonder - maybe I should use something thicker than water in that external water bath. Just thicken it. That could be interesting.
Anyway, my only fear remaining is ...what if it takes too long to heat up to the desired temp? Other than that I think you have a good point. I will keep the thermocouple on the outside. I just ordered the parts and it includes a high power 1000W bucket heater instead of travel immersion heater. I assume if that can bring the water bath to temp fast enough -I have nothing to worry about regarding the milk.
1000w will not work for a significant amount of milk/water. I use a 2500w and barely have enough power. Wayne has five 1500w I think and sailor uses two 3000w. I'm not sure how big your setup is but there is a thread on here where we talked about how to do the thermal calculations. You might want to check it out.
thanks ...but how big of vats are we talking here? This is a 5 gallon stockpot. In fact, I got the 1000W heater in the mail and it's bigger than the pot!!! I am sending it back and replacing with 2-3 immersion heaters (the ones you stick in your mug to boil water to make yourself tea when you travel).
Also, remember that in sous vide the food never touches the water so I can fill it in hot water from my faucet and begin the process at 115F so I only need to raise it by 20F-25F for most dishes
oops! I was under the impression this was a much larger setup. Just ignore my last post. hard to keep all the threads from merging in my scattered brain. :)
JD perhaps if you have a recommendation of number of watts per unit of measure? Then everyone can calculate the power needed based on their requirements.
Without putting a pencil to it, I would say about 30W per gallon would give you the ability to raise the temp 1 degree F every five minutes and 75W would increase that rate to 1 degree F every 2 minutes. This would be fine for the cooking phase most of the time. The initial heating rate with this wattage would be pretty slow so if you could get 3 elements with appropriate wattages you could conceivably operate all three during the initial heating phase (say a combined 150W per gallon with a 30W/gal, 40w/gal and a 80w/gal element), then cut back to only one (30w/gal) for the initial cooking phase, then add one more element (40w/gal) for the last third of the cooking phase or as needed. My recommendation is at least 100W per gallon but if you can't swing this, shoot for at least 50-75W per gallon. BTW, when I say per gallon, I am referring to the total amount of liquid including the water in the outside jacket. I have not allowed for heat loss, mass of the pots, kids pouring their ice tea in the jacket or other variables and I may have made a major mistake in the calculations since I am doing this in my head. My system is 40 gallons and I have a 2500W element (62.5W/gal) that doesn't meet the "1 degree F in 2 minutes" requirement and that is consistent with my practical results. I am going to rest my brain now. ;D
Awesome stuff JD as always.
Quote from: FarmerJD on December 30, 2010, 09:18:39 PM
BTW, when I say per gallon, I am referring to the total amount of liquid including the water in the outside jacket.
That's water and milk, right?
Right. My setup is about 24-25 gallons of milk to 15-16 gallons of water or 40 gallons total. I really ought to have 4000W but I get by.
Hey all!
So I finally did it and the new sous vide and digital cheese vat machine is up and running! Couldn't be happier with the result and really want to thank you all for giving me your input on this thread. Especially Sailor, Linuxboy and FarmerJD,
I started a new thread for it with photos and a complete guide. https://cheeseforum.org/forum/index.php/topic,5951.msg42962.html#msg42962 (https://cheeseforum.org/forum/index.php/topic,5951.msg42962.html#msg42962) - "DYI $100 Digital Cheese Vat / Sous Vide Machine! (Photos) - A full guide!"
In the restaurant world, we use thermometers that can be calibrated by the ice water method of 32 degrees f and boiling point of 212 degrees f at sea level. In cheese making is that critical to be within a degree or two?
Andy
Sorry for taking so long to reply. The temperature is very significant to the quality of the cheese. If this was only one process that depended on it it would not be a big deal but the acidification depends on it, the bacteria and enzyme inoculation depends on it, the drainage of whey and firmness of curd depend on it, and later, the aging process depends on it. When ALL of these are off because they are based on wrong reading, the cheese quality may suffer a lot. 2 degrees are not critical but when you go to 4-10 degrees change on ALL of these processes your cheese is worthless. Remember that this begins with bringing the milk to the body temperature of the animal producing it - to mimic the farmstead process and premium activity of bacterium and enzymes in the milk.
Last year I got a nice new thermometer and began using it for a specific cheese. It worked okay and then I began having off batches that eventually turned into cheese that was totally off (took about 4 months) When I got my new extech lab thermometer and a new candy thermometer for tall pots I decided for fun to throw them all int he same hot water. Boy, was I shocked to see the new thermometer was perfect to the 2/10th of a degree with the lab thermometer, while the thermometer I used for that cheese was 4.5 degrees off. I began using the new thermometer on the cheese recipe and what do you know, cheese was perfect ever since in every batch.
How did people test and adjust temperature closely 200-300 years ago, and probably with a wood fire?
Galileo had a reasonable water thermo-scope back in late 16th century. The mercury thermometer was invented in 1714, still the best and most reliable tool to this day. I go nuts cross checking my easy to use infrared and digital thermometers.
Were they so common that almost everyone had one, like the home thermometers of today?
There is lots of history behind thermometer, barometers, sextants etc for the ships of the day.
Mostly in cheese making in the monasteries, it was the same as it is today, extremely well honed sensory calibration of the right time to do stuff like cut the curd or drain the whey. I watch folks here in Brazil making some great cheese with no tools at all. They have many generations of doing one cheese exactly the same way. While us "Modern" folks are dependent on our digital pH meters and thermometers, these people know the proper pH point to drain from a drop of whey on the tongue. Fun to watch.
Thanks. That's what I was getting at... learning the 'sensory calibration' whereas we rely on "tools" and seldom learn the "feel".
Coffee - "Many generations of doing one cheese exactly the same way" is the point. If you do the same cheese day after day you may be able to develop sensory techniques. But, I feel that it is almost impossible to develop a true "feel" when doing several different kinds of cheese on an irregular basis. Most people do not have the ability to stick a finger in water and tell the temperature within 5 degrees, much less 1 or 2 degrees.
Right now my milk supply is changing dramatically because of Spring, new calves, lactation cycles, change in diet, etc. Without using the flocculation method, a spinning bowl and a good timer, I would be making a lot of mistakes. For example, I do 35 gallon batches and my rennet dosage has dropped from a high of 42ml per batch in January to 28ml in my batch yesterday. That's HUGE - a 33% change. And a lot of that change has happened in the last 2 weeks. So if I had continued using the 42ml that I used in January, my curds would have set too long before cutting, causing extra moisture to be trapped in the finished curds. The extra moisture would have promoted aging too quickly. As a result my cheeses could have ended up bitter and inferior. What sensory clues would alert you to make adjustments like that?
Yesterday I made Lancashire with Aroma B and a little MA11 to help with acidification. With cheddar types, and salted curd cheeses in general, the acidity at milling and salting is critical to getting a consistent texture. I drained at a pH of 6.1 and Aroma B is slow, so it took 1-1/2 hours after draining to reach a pH of 5.6 (where I like Lancashire). I have made a lot of cheddar types and I can tell when a curd mass gets below 5.4 because the curds are MUCH firmer and harder to mill. But without a pH meter, you are really just guessing and hoping for the best.
Simple tools make us better cheese makers.
Hey, I wasn't arguing against tools... I'd be sunk without them. On the other hand I do believe there are some things/places where we can really develop a feel, eventually if we choose to pay very close attention to the many nuances.
While it is cool to watch a master do his thing with no tools - in a make room not much cleaner than a barn-, I don't think many of us on this forum can get the generations of experience needed to go without tools! I'm having hard enough time with pH meter, acidimeter, mercury and digital thermometers, not to mention sterile make room.
Sailor, how did you know when and how much to reduce your rennet? I'm down to 1:12000 and thinking I could go lower. I get a clean break at 3X floc, but floc is still just under 10 min.
I try to keep my floc times at 13-15 minutes, so when it starts dropping, I add less rennet. I talk to the farmer every time he delivers milk to see how the herd is doing. He gave me a heads up that many of his cows had calved and they were beyond the colostrum. At the same time, the milk started having a yellower color (probably from the changing diet). When I tasted the milk, it started having a richer, creamier flavor. The milk seems to have become a little sweeter with less of an earthy smell and flavor. No sophisticated lab equipment here, so yes, there was lots of sensory observations going on. ;) But a lot of it was also just talking with the farmer and trying to predict how things were going to change with Spring coming on. It occurs to me that you probably don't see that same kind of dietary change in Brazil.
My delivery is 175 gallons - 5 batches of 35 gallon makes. My first make of the week is a judgement call, so when I started seeing these changes, I reduced the rennet a little to see what would happen. After the first make, I know what the floc time was and know exactly how to adjust for the remaining makes.
Going from Fall into Winter, I saw the EXACT opposite happen. Around late October my rennet dosage per batch started going up from 28ml and peaked at 42ml in January. I'm sure Pav knows the biochemistry behind the changes, but it's really just the magic of Mother Nature. I would think that milk would get richer for Winter so that calves would have more nutrition during harsh weather, but empirically that doesn't seem to be the case.
Yes, 10 minutes is a little short for my taste, so IMHO you still need to reduce your rennet.
Having not too long ago read Angela Miller's Hay Fever (http://www.amazon.com/Hay-Fever-Chasing-Vermont-Changed/dp/0470398337), she discusses a bit of Peter Dixon's role in planning out just these kinds of changes based on seasonality in their milk supply. I find this aspect of cheesemaking - something akin to your discussion of tweaking ripening time by knowing the properties of acidifying mesophilic SLABs - really interesting, and important.
Great, informative post, Sailor. Thanks for the experience points.
I met Angela through a mutual friend (her publicist) and she invited me to the farm. I was supposed to take an advanced cheesemaking school by Peter Dixon at Consider Bardwell but then I had an emergency and the next month he was busy (he got married on the farm) so I ditched it until this coming summer. Angela is very charming and interesting lady (very emotional speaking about her goats!) Their cheese is really fantastic.
If you want to get some of Peter Dixon's cheesemaking info, may I suggest to read American Farmstead Cheese (he is one of several co-authors. An excellent book full of techniques, formulas, business info about the cheese business, stories, cheese history, etc.)
Lastly, one thing she told me that stuck with me: "To become a million dollar cheesemaker overnight, start at 2 million" - love it
Sailor,
Yes being in Brazil has differences. We are heading into the last week of summer now and this means the best climate for milking is ahead in the fall and winter. Temps are cooler and less mud in the forecast. We are at 3000 ft in altitude so we never get HOT, mid 80's is a really hot day, but the cows like the 50's and 60's that will soon be the norm. Lows in the mid 30's is winter in July.
These changes, anywhere, do change the milk available and there are tools to measure fat, protein, total solids etc. I am using a nearby dairy with a full lab to analyze and I often feel I'm trying to bring to scientific numbers what "feel" and experience should be doing.
I am working on only one cheese, cheddar, to see if I can get some of this with time.
I'm still working on finding out how low I can possibly go on rennet, now down to 2.5ml/30 liter batch.
@Iratherfly: Yes, I remember you telling me this, which is what led me to her book. A nice read.
I do have, and really enjoyed, Paul Kindstedt's book, and enjoyed Dixon's chapter as well. I also picked up the back issue set of his Journal. Found some interesting things in there, particularly on international, traditional practices, and cave construction.
Joe - I am currently at 28ml per 35 gallons or .8ml/gallon. That is about .17ml/liter or 5.1ml/30 liter. So, your rennet is obviously stronger than mine and/or it's reacting very differently to your milk. Trust your flocculation point and reduce your rennet.
ArnaudForestier - what journal is that?
Quote from: iratherfly on March 14, 2011, 05:14:48 PM
ArnaudForestier - what journal is that?
I don't know which back issue ArnaudForestier is referring to, but here's a link to Peter Dixon's journal information:
http://www.dairyfoodsconsulting.com/publications.shtml (http://www.dairyfoodsconsulting.com/publications.shtml)
Brian
Thanks Brian!
I thought this was some paper magazine I didn't know about
Quote from: iratherfly on March 14, 2011, 05:14:48 PM
ArnaudForestier - what journal is that?
His collection of back issues of the Farmstead Cheesemaker's Journal (http://www.dairyfoodsconsulting.com/publications.shtml). Oude Kaas had made mention of it, and I got it some time ago.
Sailor,
I'm using Chymax Extra. The label says 1:3000. I have heard that is a number for any milk including UHT and that my milk being fresh I would need less. Tomorrow will be going down to 2ml/30liter.
Our milk gets rennet at about 45 - 60 min after milking.