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Pressure Cooker vs. Autoclave?


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#1 RedOctober

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Posted 17 August 2007 - 04:04 PM

I have only ever had an electric autoclave (All American 25x) but I was thinking of trying, as per some of your suggestions, a regular pressure cooker. Aside from the obvious difference of the autoclave being electric and the pressure cooker being “manual,” are there any other qualities that set the two apart. Does one do a better job than the other at sterilizing or require more time? Or are they pretty much the same in that respect?

Of the pressure cooker brands, Presto and Mirro seem to be the most popular. Of these, what is your experience? The Presto has a pressure gauge at the top while the Mirro seems to have built in pressure settings of 5, 10, and 15 psi but no gauge. If you could just dial in 15 psi it would be like a “set it and forget it” type of deal which seems nice. What do you guys think about either brand?

#2 goldenteacher1163

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Posted 17 August 2007 - 04:25 PM

IMO the pressure cooker is much better than the electric sterilizer because even though the electric model uses a little water it operates using dry heat. Wet heat is much better at sterilizing.
As far as brands mirro has never let foaf down but he has been looking into a new all-american 915 pc.

#3 thatballguy

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Posted 17 August 2007 - 05:31 PM

I dunno. . .hospitals, vet clinics, and tattoo/piercing studios all use autoclaves to sterilize their equipment, so I'd think it'd be fine. What capacity does your clave have?

#4 Lazlo

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Posted 17 August 2007 - 05:37 PM

If you have a 25X, use that. If you don't want to, then sell it to me. :D

And whoever suggested that was dearly wrong.

#5 RedOctober

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Posted 17 August 2007 - 10:28 PM

ballguy, my sterilizer can hold 14 pint jars and like 8 quart jars or something like that. I'm not dissatisfied with my autoclave at all, I want to use both. I really would like some more capacity to shorten the sterilizing times. I don't know how long it takes for a pressure cooker to reach pressure but it takes the electric autoclave about an hour which sux cause then it's another hour of sterilizing time followed by cool down. So one cycle takes about 2 hours.

goldenteacher, I wouldn't say that the autoclave uses dry heat. You fill the bottom with about 3 gallons of water and believe me, it gets steamy in there. When you open the thing after a cycle, everything is covered in heavy moisture and steam comes barreling out at you, which burns if you're not careful.

P.S. How fast does the pressure cooker heat up?


#6 Lazlo

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Posted 18 August 2007 - 07:32 AM

They do take a long time to heat up.

If you're looking for a good pc for cheap, check out ebay.

#7 Odin 13

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Posted 18 August 2007 - 10:13 AM

There is not a whole lot of difference between an autoclave & a PC. It's like potato or potahto. Your 25X is the Cadillac of PC's, nothing in the world comes close to All Americans, they are the gold standard. Try stacking your quarts on their sides, I can fit 10 in at a time that way(I own a 25X too.) Don't worry about screwing the lids down to keep the jars from leaking, I do it all the time without problems. My 25X is older than I am (better than 5 decades) & still works as good as the day it was made. Granted, the power cord bought it long ago, but a cheap extension cord & twenty minutes of my time solved that. Like Laz said, anything else you get told is BS, go look at a mirro or a Presto, they have gaskets which need replacing, & are nowhere as thick & sturdy as All American's. You own the best money can buy at the price, don't sweat it.
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#8 TVCasualty

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Posted 18 August 2007 - 10:21 AM

I really would like some more capacity to shorten the sterilizing times. I don't know how long it takes for a pressure cooker to reach pressure but it takes the electric autoclave about an hour which sux cause then it's another hour of sterilizing time followed by cool down. So one cycle takes about 2 hours.


For more capacity, check out the All American 941. It holds 19 quart jars or 27 pint jars per run. It comes as a Sterilizer or a regular PC (PC= much much cheaper). A typical run on the 941 takes about 3 hours, since there's so much mass to heat up and cool off, and I'm assuming a 90 minute cook time at 15 psi. Also, the larger the cooker, the easier it is to monitor; the large thermal mass means once you get to 15 psi, it fluctuates much more slowly than a smaller cooker, allowing you to do other things instead of watch a gauge.

To increase the efficiency of any cooker, put new jars into the PC as soon as you take some out, taking advantage of the pre-heated cooker to shorten the warm-up time, just make sure there's still enough water. For a 941, a half gallon (2 liters) is plenty.
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#9 Doc Chi

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Posted 18 August 2007 - 11:35 AM

:hippie:Hi: Stay with a pressure cooker! I've repaired and remanufactured steam sterilizers from back in the 80's. I have one sitting in my garage now and never use it. It takes about four hours to heat up and with a 18KW 220V heater (witch is a small one) in the steam generator you can go and watch your electric meter go nuts as your electric bill goes though the ceiling.
Also I'm a bit of an ass hole about this,:nana:I hate the term Autoclave. It's a term that comes down to us from the old French Academy of Science from over 100 years ago and it's about the door and its locking mechanism that's used on other equipment also. Over a 100 years ago a steam sterilizer looked very much an All American PC. But when they put a door on that was hinged with a locking mechanism with just one handle it was designated the autoclave. It's called a sterilizer, dam it!:eusa_wallIt can be steam, gas, some kind of hybrid unit or even gamma radiation; but there still a sterilizer and not an autoclave!:eusa_doh:
:eusa_thinAlso most hospital sterilizers are set to run at to high of a pressure as are most lab units. They're there to sterilize equipment or the used cultures from the lab. Labs that make culture medium have units that have been set to run at a lower pressure and run on what’s called a liquid cycle that very slowly drops the pressure at the end of the cycle, the exhaust time can be close to a hour long, like at BBL that runs one or more 30L flasks of medium at a time.:eusa_snoo
:eusa_shifNot like the liter or less we make. So stay with your good old pressure cooker. It will save you time and money, plus your insurance person would sit them self if they found one when they came over to renew your fire and comprehensive home owners policy.:naughty:
:eusa_naugAs for table top sterilizer units they are a pain in the butt and used ones can be dangerous. Tattoo parlors, small Doctors and Vet nary offices use them if they sterilize their own equipment because they have to by health code and law.:bow:
PS: :teeth: All American are just high end perssure cookers even the ones with heaters are just a PC with its own hot plate built in, they're nothing more or less! :hookah:
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#10 RedOctober

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Posted 18 August 2007 - 12:41 PM

Odin, glad to know your All American still works after 5 decades! I've only had mine for a few years but it has served me well. I think that repairing my sterilizer might be a pain and I dread anything going wrong with it, whereas a simple pressure cooker like a presto might be easier to get parts or gaskets for. Also, if it really crapped out, buying a new one would only run me $100 instead of $600-800 for a new All-American.

Incidentally, how many pint jars can you fit in your 25x? I can only get 14 in mine, are you able to fit more?

Doc, I used to use the swinging door autoclave that you are referring to. We had one back in school in our lab and it was like 40 years old and huge. You could probably fit a person in it. A gamma irradiation unit would come in pretty handy for mycology, I wish that they were available for personal use (hehe).


#11 Lazlo

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Posted 18 August 2007 - 01:39 PM

You may be able to steal one of the 921's listed here for damn cheap.

#12 Doc Chi

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Posted 18 August 2007 - 02:32 PM

:hippie:Hi: :offtopic:I know this a bit off subject. But I've work a steam sterilizer at the port of LA, CA that's big enough to put a land sea container in and it was a high Vac. unit to. That's one big sterilizer!:eusa_danc
:thumbup:Gamma sterilization is used a lot more than people think. I used to go to a place called Sterigenits to do the testing on their lab unit for their FDA certification on it. They can take a 4'X4'x6' pallet and srerilize it in about two mintes, no heat or mosture. :hookah:
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#13 RedOctober

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Posted 18 August 2007 - 05:53 PM

Damn Doc, I'd like to get my hands on one of those! I'll just throw it in my back yard and do 5 million jars at once ;)

I wonder if professional setups at mushroom farms use radiation to sterilize substrate? It'd sure be a time saver. I may be mistaken on this but I believe that the FDA has approved irradiation of produce but not meat. Or maybe it's the other way around. I remember seeing a company on 60 Minutes that was irradiating produce to kill all bacteria. It was right after the big e.coli scare. These guys sprayed a concentrated dose of e.coli onto spinach, enough to be lethal, then irradiated it and ate it to prove it was safe. Interesting experiment. But I digress...


#14 TVCasualty

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Posted 19 August 2007 - 10:04 AM

Pork has been irradiated for a long time, and it's why trichinosis is no longer a big problem.

One thing about it though, novel compounds not normally found in nature (and never in plants or meat) are created by the gamma radiation, which is ionizing and therefore capable of creating compounds no one has ever eaten before, and that's exactly what ends up happening. Yum!

#15 Odin 13

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Posted 19 August 2007 - 11:11 AM

I'm a grain spawn type so I have never done anything less than quarts. I often use 1/2 gallon jars & only one of those fit! I picked up my 25X in an antique store for $20 because the salesperson really didn't know what it was or what it was for. Even after telling him what it was, I talked him down because the pressure meter was gone. I walked down the street 2 blocks to a surplus store & found a brand new meter in the box for $2. I have a 921 sitting in storage as a backup so I'm sure that is why the old 25X keeps on chugging along. As long as you have a spare of something, you never need it! As far as gamma radiation, you may have a facility in your neighborhood & not even know it. They don't often like folks to realize that there are extremely high radioactive sources near their homes/families. There is just such a facility about 5 miles from where I live, & I toured it for where I worked. We actually got to go into the source room where the radioactive rods were (we had to wear dosimeters). The core was under about 12 feet of water if i remember correctly, but the water had a wierd bluish glow due to ionization. The whole core is set up to drop down into the water tank which is at ground level & surrounded by 12 feet of concrete w a 10 ton steel cap that will close it off in emergencies. I forget how many curies of material they were using, but it was ungodly. The whole thing scared the shit outta me! I realized that you can never know the kinda shit that may be going on near your own home! I lived in Amarillo, Tx. for 9 years & only heard later that Pemex has a plant there which assembeled/dissassembled atomic weapons. That explained why the russians always had a good 10 warheads targeted for the Texas panhandle!
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#16 Doc Chi

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Posted 19 August 2007 - 05:35 PM

:hippie:Hi: Opess!:eusa_doh:

#17 Doc Chi

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Posted 19 August 2007 - 05:52 PM

:hippie:Hi: I think we're making to much over gamma irradiation.:eusa_shifThe idea been around since I was child and I'm in my late mid 50's now. I was in FFA in high school from the mid to the late 60's and one of the text books we work out of was published in the early 60's that went on and on about how irradiation of food was going to be the wave of the future.:thumbup:For the reasons stated by TV its never happened and to the best of my knowledge its been never used other than in small test areas for research.:eusa_snooSo I will disagree with TV about the irradiation of pork to control trichinosis. Also to the best of my knowledge irradiated meat has not been sold here in the states.:naughty:
:thumbdown:Trichinosisis is a small worm that invades the muscles, weakening them including the heart and is parasitic to humans. It's transmitted by eating raw meat that's contaminated with the egg cysts of trichinosis that's in it.:eusa_naugIn the past there was a practise of feeding raw tankage (the meat scraps and other parts left over after slaughter) back to the hoggs tell that late 60's. After that point tankage needed to be pasteurized to kill off the cysts in it. Irradiation may have been used at that point in some places as it was being feed back to hoggs and not people.:eusa_shif
:eusa_thinAs for compost used on mushroom farms it doesn't need to be sterilized, as it's self pasteurizing.:offtopic:There is no need to say any thing more at this time.:eusa_clap
:hookah:

#18 RedOctober

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Posted 19 August 2007 - 08:44 PM

I recall my father saying that back in the 50's it was thought that irradiation would replace or at least be used alongside of refrigeration....guess not! Like TV said, the ionizing radiation is producing chemical changes in molecules which may or may not be harmful to humans. I believe more research and testing is required in this area.

Incidentally, getting back to my original topic, I just went out to Walmart and bought a 16 quart Presto. I says to pour water into the bottom but I believe that would mean I can't tip jars onto their sides or they'll be under water. How do you orient your jars for max efficiency? The box advertises that it can hold 10 pint jars, is this really so?


#19 TVCasualty

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Posted 20 August 2007 - 06:35 AM

So I will disagree with TV about the irradiation of pork to control trichinosis.


The FDA has approved irradiation of pork, although no one is currently doing it, so you're right about it not actually happening. I must've read about it in a context where someone said it was approved and was strongly implying that that meant it was being done.

I found a handy FAQ about the subject, which does nothing to address the issue of choosing an autoclave vs. a pressure cooker:

http://www.physics.i...radinf/food.htm


Ten Most Commonly Asked Questions About Food Irradiation

Food Fact Safety Sheet

By Charlotte P. Brennand, PhD, Extension Food Safety Specialist
March 1995 FN-250.8

1. Why is food irradiated?

Food is irradiated to provide the same benefits as when it is processed by heat, refrigeration, freezing or treated with chemicals to destroy insects, fungi or bacterial that cause food to spoil or cause human disease and to make it possible to keep food longer and in better condition in warehouses and homes.

Because irradiation destroys disease-causing bacteria and reduces the incidence of food borne illness, hospitals sometimes use irradiation to sterilize food for immuno-compromised patients.

2. Are irradiated foods still nutritious?

Yes. Irradiated foods are wholesome and nutritious. All known methods of food processing and even storing food at room temperature for a few hours after harvesting can lower the content of some nutrients, such as vitamins. At low doses of radiation, nutrient losses are either not measurable or, if they can be measured, are not significant. At the higher doses used to extend shelf-life or control harmful bacteria, nutritional losses are less than or about the same as cooking and freezing.

3. Does irradiation make food radioactive?

No. Radioactivity in foods can occur by two routes: contamination of foods with radioactive substances or by penetration of energy into the nuclei of the atoms that make up the food.

The irradiation process involves passing food through an irradiation field; however, the food itself never contacts a radioactive substance. Also, the ionizing radiation used by irradiators is not strong enough to disintegrate the nucleus of even one atom of a food molecule.

4. Does eating irradiated food present long-term health risks?

No. Federal government and other scientists reviewed several hundred studies on the effects of food irradiation before reaching conclusions about the general safety of the treatment. In order to make recommendations specifically about poultry irradiation, U.S. Food and Drug Administration scientists reviewed findings form additional relevant studies.

Independent scientific committees in Denmark, Sweden, United Kingdom and Canada also have reaffirmed the safety of food irradiation. In addition, food irradiation has received official international endorsement from the World Health Organizations and the International Atomic Energy Agency.

5. Does irradiation destroy all bacteria, resulting in a sterile produce?

Irradiation, at the levels normally used in food processing, destroys most, but not necessarily every single microorganism present; it does not sterilize the food.

As with any food, consumers must take appropriate precautions, such as refrigeration and proper handling and cooking, to make sure that potentially harmful organisms do not present a problem.

After treatment, the surviving disease-causing and food spoilage organisms may start to multiply again if the food is not properly handled. The disease-causing organisms in irradiated food are just as dangerous, but not more so, as the same organisms in non-irradiated food.

One concern has been that irradiation does not kill the bacteria that causes botulism. However, studies also have shown that in both irradiated and non-irradiated food, spoilage organisms will grow and alert consumers to spoilage before botulism-causing bacteria can produce toxin.

6. Does irradiation cause chemical changes in food, producing substances not known to be present in non-irradiated food?

Yes, irradiation does produce chemical changes in foods. These substances, called "radio-lytic products", may sound mysterious, but they are not. They have been scrutinized by scientists in making safety assessments of irradiated foods. Any kind of treatment causes chemical changes in food. For instance, heat treatment, or cooking, produces chemicals that could be called "thermolytic products." Scientists find the changes in food created by irradiation minor to those created by cooking. The products created by cooking are so significant that consumers can smell and taste them, whereas only a chemist with extremely sensitive lab equipment may be able to detect radio lytic products.

7. Will my risks of radiation exposure increase significantly if I live next to an irradiator?

No. The use and transportation of radioactive materials, including the facilities in which they are used and the equipment in those facilities, is closely monitored by the Nuclear Regulatory Commission, state agencies and the Department of Transportation.

The radioactive material itself is sealed within two layers of metal that prevent corrosion and oxidation. When shipped, it is placed within brick layers of lead that prevent gamma rays from escaping.

Facilities must include many safety features to prevent both environmental and worker exposure. For example, when radioactive cobalt is in the storage position in an irradiator, it is under water and otherwise shielded. The irradiator is operated by remote control, and many other protections are required to prevent workers form entering the irradiation enclosure.

8. For what other purposes is irradiation technology now used in the United States?

In addition to cancer treatment, irradiation is used for many purposes, including: performing security checks on hand luggage at airports, making tires more durable, sterilizing manure for gardens, making non-stick cookware coatings, purifying wool, sterilizing medical products like surgical gloves, and destroying bacteria in cosmetics.

9. Are irradiated foods on the market now?

Until recently, only irradiated dried spices and enzymes were marketed in the United States. In January 1992, irradiated Florida strawberries were sold at a North Miami supermarket. Sales of irradiated products are ongoing in several grocery stores. Poultry irradiation began commercially in 1993.

Irradiation of food has been approved in 37 countries for more than 40 products. The largest marketers of irradiated food are Belgium and France (each country irradiates about 10,000 tons of food per year), and the Netherlands (which irradiates bout 20,000 tons per year).

10. How can irradiated foods be identified in the market?

Irradiated food cannot be recognized by sight, smell, taste, or feel. Irradiated foods will be labeled with a logo, along with the words "Treated with Radiation", or "Treated by Irradiation."

(This publication includes information modified from the Food Inspection Service, USDA, information on irradiation.) Utah State University is an Equal Opportunity/Affirmative Action Institution. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Robert L. Gilliland, Vice President and Director, Cooperative Extension Service, Utah State University, Logan, Utah. (EP/3-95/DF)

(emphasis mine)

I am a little concerned about their answer to #6. Yes, cooking produces macro-changes in food that are easily detected (mouth-watering smells from the kitchen), but those are changes made by low heat that produce known and naturally occurring compounds (although charring meat on a grill produces carcinogens, though it still smells great). Radio-lytic changes, they admit, produce novel compounds but in small amounts, however the amount of something in my food means nothing; the question to ask is "How toxic/potent are these compounds?"

You might need a big fancy lab to "detect" the radio-lytic products, but detectability in a lab is irrelevant to their possible effects inside a body!

#20 TVCasualty

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Posted 20 August 2007 - 06:52 AM

Incidentally, getting back to my original topic, I just went out to Walmart and bought a 16 quart Presto. I says to pour water into the bottom but I believe that would mean I can't tip jars onto their sides or they'll be under water. How do you orient your jars for max efficiency? The box advertises that it can hold 10 pint jars, is this really so?


Oh yes, the topic. Back to it, then!

I don't put jars on their side, but I do sometimes put a stainless steel pot in the cooker as a liner. It reduces the number of jars it can hold, so I mainly use it for sterilizing tools, or to keep spawn bags from touching the sides of the cooker which can melt them if it gets too hot, plus it keeps the water off the bags and I can lift the whole load out at once. The trick is finding a pot that just barely fits inside the cooker. I had to bend the side handles of mine to fit it inside, but it's worked great.

I guess it's not really an advantage in this case, since you reduce the number of jars you can cook when you put a liner in (so that you can lay jars on their side to increase the number of jars you can cook). Sorta cancels itself out I guess, but still, a liner pot for your PC is very handy, especially for PC'ing tools (scalpels, spoons, LC jars, airports, stuff like that).

A cooker doesn't need very much water, so laying jars on their sides even though there's water in the PC would be fine so long as you didn't put in too much, obviously. I'd try to figure it out using empty jars for testing, since my initial tests of anything always fail! (If the empty jars start to float, there's too much water in it)




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