Chemicalkinetics! IS IT SAFE? PVC piping used for cheesemaking press.
- Mr Taster May 13, 2013 02:16 PM
First of all, I hope that cheesemaking falls under the "Cheese" board and not the "Home Cooking" board, because that's what my question is about.
I've just started dabbling in home cheesemaking, and this weekend I made my first farmhouse style cheddar. It's currently resting under a crazy ramshackle press I rigged up with four X 5 lb. free weights sitting on top of a cheese mold follower. It's already come crashing down twice.
So, I've turned to the Internet for a better solution. Lots of people offer suggestions on making home cheese presses, but I kind of like this one:
I live near the store that can supply all of these parts, so was thinking of making it myself.
However, the cheese press uses lots of plastic parts, like PVC pipe and polyethylene.
Ricki Carroll, the "cheese queen" of New England (according to her story, she's to home cheesemaking what Alice Waters was to the "slow food" movement) says PVC leeches an aftertaste into cheese. When I asked the PVC press guy about this, he said he once contacted Ricki about selling his press through her, and she went off on a tirade against the oil industry. He told me, "This stuff is used all over the world for handling drinking water, food and milk products and is classified as "food grade"."
So, my question to you is, are the plastics used in this cheese press safe to come into direct contact with food? A rudimentary google search indicates that there are different types of polyethylene, and some are safer to use than others.
Of course I'm looking to ensure that the plastics I'd use in this specific application are safe and will not leech (i.e. warm or room temperature acidic curds in direct contact with PVC and polyethylene, for an extended period of time-- 24 hours)
I would particularly like to hear from Chemicalkinetics, since I know you have a scientific training and likely know a bit about this topic. I'm looking for facts, not speculation or anti-oil/anti-plastic tirades.
Hi. Mikie probably knows more than I do, since Mikie is/was a plastic guy -- an engineer/scientist who worked with plastic and wrote handbooks about various plastic.
PVC pipes are indeed used for drinking water and all. All in all, I would say it is pretty safe. You are not really heating the PVC pipe to a high temperature, right?
<PVC leeches an aftertaste into cheese>
It is possible I guess for a brandnew PVC pipe with plastic smell. I doubt if unplasticized polyvinyl chloride (uPVC) would help in this regard. Hopefully, Mikie will drop by.
I read that online. As I said in my reply to Chemicalkinetics, the PVC will contain only warmed curds, and will not be heated directly.
By the way, here's the link to Ricki Carroll's (the "cheese queen") page on PVC. See question #5. According to the cheese press guy, her response is due to her anti-petroleum position (though she does sell plastic molds imported from France for outrageously high cost).
No, we're not heating the PVC pipes directly, however they will be in direct contact with warm (~85 F), acidified curds (pH ~5.1) for 24 hours.
If you look at the blueprint diagram on the linked webpage, you'll see the press is a simple mechanism-- you ladle the drained curds into the tall PVC chamber, which sits on a polyethylene base. The curds are then pressed at a designated weight by a polyethylene "follower" (which is a flat surface that presses the cheese from above) for about 24 hours.
I don't know that I've read Mikie's posts before... I'll search him out.
I appreciate the accolades, still in the plastics business. In short there are FDA grades of plastics and grades of the same plastic that are not FDA compliant. Yes, PVC caries a lot of water, but I'm not sure that the 6 or 8 inch diameter pipe is the same grade as 1/2 inch water pipe. Most PE (polyethelyne) is food safe, that's what most plastic cutting boards are made from. It's also used for water distribution. Most new construction uses crosslinked PE these days. At the temperatures you are talking about, there shouldn't be any issues with leaching chemicals, but I would still look for a food grade plastic. Plastic materials can contain a lot of additives, mold release, plasticizers to aid flow, pigments for color, etc. so you need to be picky about what specific grade of PE or PVC that you use.
I see the guy on the chesepress web site doesn't like wood, a long time ago I made a small apple cider press, very similar to the cheese press, but with wooden slats wraped with an aluminum ring, kind of like a barrel, and with an acme threaded screw press, similar to what is used in a vise. It worked great for pressing apples. None of the issues mentioned by the cheese press guy. Hope this helps, good luck.
Hey mikie, thanks for chiming in.
I actually decided on making an even simpler cheese press, where the pipe doesn't even come into direct contact with the cheese:
As you can see, this uses a regular cheese mold, and the PVC piping is only used as a spacer/riser for the follower (the plastic "plunger" disc that compresses the cheese), so it doesn't need to come into contact with the cheese itself. This seems to be a great alternative.
You can see a picture of the mold and the follower here:
The 4" PVC is a perfect fit over the round riser.
So last night, I was as at Home Depot last night looking for the 4" PVC pipe and found only 4" ABS pipe. (They did not have 4" PVC). They explained ABS pipe is for "dirty water" as it can handle Drano and other acids that "clean water" PVC pipe cannot handle. This of course gave me concern. Although the ABS pipe doesn't come into direct contact with the cheese, I am still concerned that the acidic liquid whey could leech up onto the top of the follower and come into contact with the ABS pipe, and slowly marinate the cheese. The workaround for this of course would be to wrap the ABS pipe in Glad wrap or some other food grade plastic, but I'm still curious enough to ask the question-- is ABS pipe more toxic than PVC?
re: Mr Taster
Here's the tricky part with plastics, there are literally hundreds of thousands of grades of various plastics. Many are formulated for very specific end uses, many are what is commonly refered to as "general purpose". In commercial applications, which are entirely different than home use, certian criteria must be met to ensure food and potable water safety. Some of the standards that apply are NSF Standard 14 "Plastic Piping System Components and Related Materials", Stnadard 61 "Drinking Water System Components" (this might include faucet materials), and Standard 51 "Food Contact . . ." The bottom line is that there are formulations of jsut about any plastic material that can and do meet certian food contact standards under certian conditions.
ABS pipe is normally usen in DWV applications (drian, waste, vent) and would not necessarily need to be food contact safe. Based on some of what I see here: http://www.hc-sc.gc.ca/ewh-semt/water... I probably wouldn't be very anxious to use "unknown" ABS. Not that it contains "tetra ethyl death" but the A stands for acrylonitryle.
"Acrylonitrile is a non-regulated chemical. The action level was set based upon its classification as a B1 carcinogen. Acrylonitrile is typically associated with acrylonitrile-butadiene rubber compounds (NBR) and acrylonitrile-butadiene-styrene plastics (ABS). A typical use of the NBR is in the formation of "O"-rings for gasket purposes, which commonly have a water surface contact area of 2 square inches or less per liter of water. ABS materials are used to make faucet bodies, pipe, fittings and other smaller pieces that are used in various mechanical devices.
The extraction of acrylonitrile from NBR products appears to be dependent upon the manufacturer's formulation and production procedures. Numerous manufacturers consistently have significant hits of acrylonitrile, resulting in an end failure of their material. However, there are also manufacturers that do not have any detectable levels of acrylonitrile extracting from their product. The curing process has been shown to be critical factor in the extractability of acrylonitrile.
In ABS materials, the extraction of acrylonitrile appears to be more of a function of the surface area of exposure and not necessarily the specific manufacturing process."
So that's my story and I'm sticking to it. Good luck with the cheese press.
re: Mr Taster
II'm not anti plastic obviously, it's sent 4 kids to college and kept me at least comfortable, but in your case, finding the right plastic for the job at hand may be an issue. If you can find PVC water pipe approved by NSF Std. 14 or 61 you're probably going to be ok.
One more little piece of information, exposure time and temperature are very important. The lower the temperature the less happens, this is the same with BPA, PTFE, etc. Also the shorter the exposure time, the less likely there will be any leaching or chemical attack.