Thursday, August 23, 2012

Let's talk curing chambers

I've received many many emails asking about specifics of my curing chamber, and more specifically about using different types of refrigerators to use as a curing chamber, so I wanted to post some quick information on choosing a fridge.

The general idea when we're turning a fridge into a curing chamber is that we want to control temperature, through a temperature controller, and humidity, through an ultrasonic humidifier and a humidity controller. In order to do this the fridge has to run "dry" so that we can add moisture back to the level of our choice, generally 70%-80%.

Easy enough, right? Well, sort of. Most normal, large, kitchen refrigerators, run "dry". Basically, they work by blowing air over a cold evaporator coil, and direct it into the fridge. Since the evaporator coil of a fridge is rather chilly, the moisture in the air condenses out, and the air that ends up in the fridge is very dry. At the same time the water which condensed out of the air onto the evaporator coil freezes and needs to be melted off periodically and directed out. This is exactly what a "frost free" fridge does. Every 12 hours a small heater wire melts the ice which forms on the evaporator coil and the water is collected and directed out to a pan where the water can evaporate back into the environment. So, in the end we have a "dry" fridge, which on it's own would normally run somewhere around 20-40% RH, we add humidity back in and control temperature, and voila'! curing chamber.

The questions arise when people start wanting to use standup freezers, chest freezers, or compact fridges such as the ones used in dorms or wine refrigerators (since they conveniently run at temperatures suited for what we need) or some other kind of system for their curing chambers. The two most common questions about fridges are in regards to wine fridges and compact refridgerators, and whether they can be used. The simple answer is.... sort of. Let me explain.

All the compact and wine fridges I've see have one thing in common which makes them very different from the standard fridge I recommend for curing. They cool not by blowing air over an evaporator coil but by cooling the fridge directly via a cooling plate inside the fridge; just a metal plate with channels in it in which the refrigerant runs. You can often see the metal plate at the back of the fridge, or if the compact fridge has a "freezer" section at the top, that's what cools the fridge. The problem with these is that the cooling plate does work to cool the fridge, and it does condense the water out of the air (remember we want a "dry" fridge so we can rehumidify) but the water isn't removed from the refrigerator section, at least not very well. The water condenses out; some does drip away into a collection tray, but most re-evaporates right back into the chamber, so we're back where we started.

Wine fridges generally cool using the same principle, at least the ones I've seen, they use a cooling plate inside the refrigerator section.

The bottom line is that these compact refrigerators, from what I've seen,  have no good way of extracting moisture from the air and keeping it out, which means when you put meat in there to lose water, the moisture loss has no where to go, and ends up making the fridge more and more humid as your products dry.

Are there ways to get them to work? Sure, there are, I haven't given them much thought because I haven't had to. You'd have to figure out a way to dehumidify to a specific level. If you want to try, give it a go, but I have to tell you I'm not sure how to do it, so...sorry! I know for example, as I've said before one can buy beads and sheets which absorb and release moisture to maintain a humidity of choice, or that a tray of wet salt will maintain about 75% RH. I have no idea how effective these things are though and how fast they actually work.

What about standup freezers? Well, looking at my standup freezer, it does look like it would work. Mine doesn't have a cooling plate, it blows cold air in through a vent, so I have to assume there is an evaporator plate somewhere cooling that air before it gets to the freezer ( add to that that it's a frost free freezer and i'm even more sure about that). But, i have never measured the RH in there and I don't know how it would do or what it would do running at 55 deg. F.

How about beverage fridges with nice sliding glass doors? Well, I know that Scott at Sausage Debauchery has successfully converted one of those, but I don't know how he did it. I do know that he was pulling his hair out for a week to get it to work properly.

How about chest freezers? I don't know, I don't own one so I don't know what cooling method they use.

I'm sure there are 100 different types of refrigeration systems, and I cannot possibly know if every one will or will not work. The first questions you should ask yourself is "Does this fridge have an evaporator coil outside the refrigerator section which will dry the air before it blows into the fridge"? If the answer is "Yes", then the fridge SHOULD work. If it doesn't, well, you're on your own to figure it out:)

Good Luck!

55 comments:

matt said...

I use two fridges. I have a very tall (6ft) wine fridge which has pretty much an air conditioner in the top which blows cold air down. It is great, but falling apart. The best thing is that I can set it to 55F without the need of a separate temperature controller. My other is a more standard fridge setup, into which I have drilled a 4" hole on one side with a CPU fan over it. Small holes drilled in the other side. I have that hooked up to a timer to extract humid air.

Both have their pluses and minuses, neither, frankly, is perfect. I generally prefer the larger wine fridge - it holds more, and is simple.

I am looking at going the sliding door beverage fridge route - a double door one. Most you get can a new thermostat for so you can run it at 50-60F without the need for an external controller, which I guess can really wear those pro units out. As for humidity control in that? Well I would love to come up with a "plumbed in" solution, so I don't have to keep pouring in gallons of distilled water.

jaymo said...

Most chest freeezers need to be defrosted a few times a year, implying they don't extract any moisture and thus wouldn't be a good choice.

There is probably a way to build a collar around it, similar to what people do to install tap handles for serving beer, and then rig up a fan to circulate air/moisture out, but it seems to me at that point it's easier to go out and track down a used fridge.

Max said...

I've also gone with the wine fridge mainly, as Matt points out above, because you don't need a separate temperature controller. I tried the beads for humidity control and they do work to some extent, but I've had far better success with just a saturated salt solution in the bottom

Jackson Peel said...

I've used a wine fridge before and tried both trays of rock salt (rotated out every couple of days) and a bead-based dehumidifier (designed for a closet). Both were a hassle and not terribly effective. Now that I know what the problem was, I'd experiment with opening the door to circulate air more often. (Might open it up to bad mold, though.)
I made a bresaola that turned out incredibly well. My theory is that the higher humidity slowed down the curing which gave the flavors more time to penetrate. Not sure if that's scientifically accurate, but it was the best bresaola I've ever had.

Jasonmolinari said...

i agree with your finding that longer time in drying gives better flavor. That's why i run my humidity pretty high, closer to 80% normally.

Twinkles said...

There are dehumidifiers which you can use a controller with to handle any excess moisture in the fridge. http://amzn.com/B000H0ZDD2

Jasonmolinari said...

Thanks Twinkles, that's very interesting. It works just like a fridge, but cooling a plate and collecting the condensed humidity.
I didn't realize they made this kind of dehumidifier!

Anonymous said...

Hi there I'm finding my wine fridge even with a salt solution is only running at about 45 to 50 % humidity. With a couple projects inside, why do you think this may be

Paul said...

When I first started tentatively curing a couple of years ago (stealing your recipes) I had no equipment and no room to put any. I make sure I get the necessary warmth and humidity for fermentation when necessary by making the kitchen a bit warm and steamy but other than that I just cure everything in my flat in West London. The results have always been good but of course vary between seasons.

Portland Charcuterie Project said...

I built a curing chamber out of a dorm fridge last year and with the temp/humidty mods it worked well.. that being said, 90% of the stuff I make ( proscuitto, salamis, coppa, lonzino) just gets hung up in my mancave ( my freestanding garage converted to living space a few years ago).. it's hot in the summer (up to 100 degrees on a few rare days, but mostly in the 80's ) and I keep the heat on in the winter to keep it at around 55 in the winter.

All my stuff has turned out phenomenally and so I tell most of you not to worry a whole lot if you don't have a curing chamber. When I was in italy last year, I visited a friends farm and the dad had his charcuterie hanging in a room in the barn, which was ridiculously hot and all of his stuff turned out beautifully.

That being said.. follow the established instructions, and remember that black and green mold is bad!

Andrew said...

I have been using an upright freezer that I converted a couple months ago. No cooling plates, it blows cool dry air in. It works great the the humidity stays pretty constant.
I'll be putting a lonzino in Wednesday.

csxtian said...

PCP, I have to be honest, keeping any meat at 80,90 or 100 degrees is really pretty dangerous and creates quite a playground for bacteria. While you may see fluctuations of temperature in 300 year old caves that could potentially hit the 80 mark, consistently they are well below that.

In addition, fat will begin to leak and melt significantly at that temperature and result in a lot of loss and drip, and if making salumi, a terrible bind with the fat leaking.

I can't see how any sort of control and even drying would be achieved at that temperature and would expect that you would dry incredibly too fast.

The last two things aside, I would caution anyone keeping a meat product at 80 or higher of a high risk of bacteria, especially in the early stages. There is a reason the Health Department pushes restaurants to get below 40, disagree or not, it is a safe zone. While you can push to 50 or 55, those higher temperatures just make me cringe.

Also note that the starters you use will usually die at anything above 75, as they are not intended to tolerate temperature extremes.

Jasonmolinari said...

I;m kind of with csxtian on the temperatures. I personally would avoid temps above 60.

Anonymous said...

I just finished setting up a fridge as a curing chamber. I dida similar setup for the interior plug. Have you seen any issues with the high humidity and possible electrical issues? I bought a Dayton 1UHG3 humidifier controller to run my humidifier. I'm thinking to stop wild swings in humidity, I can set the humidifier at a lower setting so it doesn't over saturate the air and let the Dayton do its intended job. Was wondering If your humidifier has its own output control and how you have it setup. I'll know for sure when I get my hygrometer in that shows daily highs/lows.

Bob

Jasonmolinari said...

I haven't run into electrical issues, BUT, i can't say it's the safest thing in the world. Use at your own risk:)

Bob said...

Jason, I've seen it mentioned for air circulation/exchange that you can either just leave the door cracked, or you can drill ventilation holes in the sides. I was thinking about going the hole route. What I haven't seen mentioned was the size of the holes. Got any suggestions?

Jasonmolinari said...

Bob, i just open the door every day or 2...i don't worry too much about it as long as it's refreshed every so often.
Not sure how big you'd want the holes and how many..maybe 4-8 1/2" holes?

Bob said...

Thanks. I travel a bit for work which would limit the amount of door opening I could do. That's why I was thinking of the holes. I'll start with two 1/2" on each side and see how that goes. I can always add more.

Gluten Free Biscuits said...

There are fridge that are intended for meat use only. The meat will stay fresh for a long time if they are place at the right fridge.

gutscheine zum ausdrucken said...

very good comment

Anonymous said...

I'm a newbie to curing so I have a couple of questions as I start out. I have my eye round cured for bresaola (11 days) and am ready to dry. I was planning on drying in my garage frig. For about 2 to3 weeks or about 30%weight. Any pointers to helpe stay out of trouble? Thanks. Larry

Jasonmolinari said...

Larry, that's a vague question. Make sure your humidity and temperature are in the right range (55F and 65-80 %RH) and watch for bad molds (wipe with vinegar/water solution)

Kenth said...

So have i made my curingchamber.
http://borglunds.wordpress.com/2012/03/05/fermenteringsskap-klart/

Jasonmolinari said...

Looks awesome Kenth!

sky said...

Jason, love your blog, thanks for the information. I just recently set up a curing chamber using a commercial under-counter fridge. It has a built in fan which runs all the time to help dry out the meat. My first cured projects have been coppas. The first one I made in my wine fridge turned out perfect, dried in about 5 weeks. My new set up has been running at 55 degrees, and a range of 60-90% humidity, depending on weather the compressor is running. My two new coppas have been curing for 2 weeks now and one of them is already down to 30% loss of weight. I was very surprised by how fast the weight has gone down. I did not use any casings, it is just the coppa. My curing time in the fridge was 2 weeks, and the weight was just a bit over from the raw weight. Also I do not have any humidifier in my fridge because the commercial fridge seems to run a high humidity normally. Is there any issues with the meat dry curing so fast? if there is no case hardening and besides the fact that the meat would taste better on a longer cure, do you have any thoughts. Do you think a lower temp would help slow down the curing, around 50? I know that a casing would help, how about bactoferm 600? Any thoughts or insights would be helpful. I was planning on letting the meat cure to 35% loss before pulling so I can let you know how it turned out then. It smells great and no mold, so everything seems good. Thanks, Skyler

Jasonmolinari said...

Skyler, a cooler temp may slow it down a little, yes, but i'm betting the constant fan is speeding it up quite a bit.
I don't know of any issues of such a short dry time, other than the fact that much of the nitrates wont have converted to nitrites and nitric oxide yet, but i don't think that should be a big deal.

A casing and mold would definitely help as well.

sky said...

Thanks Jason, I'll look into some options for slowing down the curing time. Cheers, Skyler

Anonymous said...

Thanks Jason for your amazing blog and for sharing your experience.

Just to add a bit from my experience, you mention

"The water condenses out; some does drip away into a collection tray, but most re-evaporates right back into the chamber, so we're back where we started."

You are right about this but since I had a 40 years old refrigerator at my garage I simply drilled a hole and connected a hose to the tray to drip condensed water to a bucket outside chamber. I connected in parallel the controller outputs of high humidity AND high temperature so compressor turns on either when humidity or temp is high. Chamber constantly removes humidity instead adding, usually turns on for 3-4 minutes every 30-40 minutes. I have excellent results and I think that if someone has a "old type" refrigerator should give it a try.

Jasonmolinari said...

good thinking! Thanks for the info.

Kenth said...

I try to explain the dehumidification

http://borglunds.wordpress.com/2013/01/13/how-to-dehumidificate-the-curing-camber/

Anonymous said...

Kenth you cannot dehumidify with a heating element because water vapors are stil in the chamber. You simply raise temperature keeping the water vapors constant therefore lowering Relative Humidity.
You can find info about Relative Humidity here http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.html

John

Anonymous said...

After giving some thought what is really happening is that with the heating element you force refrigerator to turn on, condense water vapors and eventually lower RH.

John

Kenth said...

I am very familiar with the condensation process but still it´s working to reduce the RH with my techniq. Anyway i shall se on the page you send. To use a salt to take care abaout the moisture is a bad idea, it will be saturated immediatley. You maybe have a point abouit the heating and condensation, but my temp is not increasing more then 0,2-0,3°C.

Many people mix the absolut humidity with the relativ humidity.

Anonymous said...

Kenth ofcourse your technique is working as it lowers RH, I just tried to understand the physics behind it. Looking at the graph from your system http://borglunds.files.wordpress.com/2013/01/luftfuktighet-lc3a5g.jpg?w=1200&h= I notice that when RH drops temperature also drops after a few minutes. If you have some spare time watch your system when starts to dehumidify to see if refrigerator is turned on when RH starts to fall.

John

Anonymous said...

How can I measure what humidity % is in he fridge?

Jasonmolinari said...

you need a thermohygrometer. Look in the list of recommended accessories i have listed.

Ross Nesbitt said...

Hi Jason,

You will have to excuse my naivety and inexperience! I have managed to procure a little under the counter fridge. inside it does have the freezer compartment at the top. I have the Model number and googled my heart out but i just cannot find anything definitive saying weather this is going to be good enough to use as a curing chamber. it does have a radiator looking bit of metal on the back of the fridge, but there is also a tray under the freezer compartment (i assume to catch dripping water from from not so frozen products) can i assume this is going to be OK to use? I will be plugging it in tonight and leave it to run for 24 hours and check the humidity then... the model though is a zanussi ZFC 50/2

Jasonmolinari said...

Ross, you're going to run into the same problems i describe above with standard mini-fridges. You'll likely be dealing with high humidity once you add product with no real way to lower it.

Ross Nesbitt said...

Hi Paul, I live in west London myself. You will have to share your experiences!

Brad said...

Great Blog! Thanks for all your valuable information.

I have a question regarding the best way to remove humidity from a cantina (hope this is the proper forum for this question)...I'm a bit limited in what I can use because I have no control of the temperature being that I need to rely on the outside environment for that. Is there anything I can place in the cantina that will remove humidity without creating heat like a dehumidifier would?

Thanks in advance.

Jasonmolinari said...

Brad, what temp and humidity is your cantina? Can you open any windows / doorways?
trays of salt should absorb some humidity but if you have a big cellar that might not be feasible.

Brad said...

Right now the temp is holding at 45 F and humidity is around 92%. I have at each end of the cantina a 4" port to allow air flow. What I have been doing is cracking the door slightly to allow some humidity to escape and for the most part it works. The size of my cantina is 14' (l) x 6' (w) x 8' (h). Sometimes it gets tricky cracking the door because of the temp being in the right zone (50-60) - I don't want it to get too warm in there...I was just hoping that there was some sort of product that I could place in there to remove the excess humidity (like salt)...

Jasonmolinari said...

brad, other than cheap salt or an expensive air conditioning dehumidifier, not sure i hve much advice.

sansei said...

my curing chamber is a converted 2 door reach-in commercial fridge. somehow, the digital controller for the fridge went south and froze the whole box. 4 coppas and 2 culatellos, frozen solid. they were only in for 2 days. if i thaw them, do you think they will still be good? if so, i'll probably use my old curing chamber(small, but very reliable.)

Jasonmolinari said...

sansei, they should be ok...just let them go and find out...

Aaron said...

Thanks for all the great info! At my restaurant we have about a 10'x4' space that was originally made to dry pasta. That never happened and now I'm wondering if it is suitable to dry salumi. The one thing is, I'm not sure the walls would be conducive for a proper cure without introducing bad mold. The front wall is glass and wood, the back is the original brick. So really, I'm concerned about the brick. The space also already has the professional cooling and humidity units built in.
Any ideas or links to another source of info?
Thanks

Jasonmolinari said...

Stone is the ideal material, so i would think brick would also be pretty good for a curing area.

Max said...

Agreed - sounds ideal! If you are really worried about contamination you could disinfect with an appropriate cleaner. The best thing to do is probably to give it a clean, then make something to put in there and just see what happens. You'll then know what parameters need tweaking

Anonymous said...

hey Jason how would I get a hold of Scott at Sausage Debauchery to find out his specks for the sliding door chamber. im in need of more room for my meats and want to build one out of an old pepsi fridge.

Jasonmolinari said...

Come join the Sausage Debauchery facebook group. Scott is there and it'ls a good place for discussions.

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jmay said...

I have just built a curing cabinet out of a single door, glass front beverage fridge. I run into many of the issues you have mentioned. My biggest issue is too much humidity. Even though the temp inside stays between 12Deg C and 15 Deg C there is still icing on some of the inner walls where the cooling tubing runs.

I also bought a line in humidity and temp controller (2 plugs in one) but it is a pain.

Ultimately I just put a 6 inch computer fan on the bottom of the cabinet and have left the door cracked open about a half an inch (my mother used to chastise the hell out of me for leaving a fridge door open for more than a few seconds :))

Needless to say, the door left open a 1/2 inch crack, with the fridge on the warmest setting is keeping me at around 70% RH and an average of 13 - 14 Deg C.

I say average because I have 2 analog thermometer/humidistats in there and 2 digital ones and for crying out loud each of them gives me a different reading so I just need to guess the real numbers are somewhere in the middle.

I guess the question is this, is there ultimately any problem with leaving the fridge door open in this instance if I can keep the numbers where I want them or am I missing something?

Jasonmolinari said...

Jmay, no issue with leaving door open, assuming the chamber isn't in a smelly garage or some other strange area where bad aromas will get in.
In fact, it's good to have a fresh air input

jmay said...

Hi Jason:

Thanks for the response. I finally got the 2 plug line in controller working (one for humidity and one for temp). As you pointed out in one of your posts the humidity goes up whenever the compressor goes of but I am keeping an average humidity of 70%.

Another question though; I mixed 450ml of distilled water with 10 grams of Mold 600 and have sprayed all of it on the salami over the period of a week but there is no bloom, no beautiful white mold even beginning to grow on the outside of the salami. Any ideas?

Jasonmolinari said...

Jmay, the best bloom temp is going to be around 70 deg or so..blooming happens quite slowly at chamber temps.
If there is no bloom at all, it's likely the culture is dead