"Discover Cooking, Discuss Life."

Go Back   Discuss Cooking - Cooking Forums > General Cooking Information > Farm to Table > Canning and Preserving
Reply
 
Thread Tools Display Modes
 
Old 04-11-2013, 02:10 AM   #1
Assistant Cook
 
Join Date: Apr 2013
Location: South Texas
Posts: 8
"Can" I take the "pressure?"

Can anyone explain to me the pros and cons of pressure canning? My mother always canned over an open fire out side using a big wash tub. When I was showing my daughter and son in law how to can tomatoes we had lots to do and was tempted to use that same method.
I am seriously looking into buying a pressure canner but not sure if the expense is worth it or not. I have been looking and dang... them things are expensive! I know nothing about them. Zilch.

__________________

__________________
The most important thing we can do to save cats and dogs from all the suffering and death that their overpopulation causes is to spay and neuter them
nana9 is offline   Reply With Quote
Old 04-11-2013, 04:09 AM   #2
Sous Chef
 
no mayonnaise's Avatar
 
Join Date: Oct 2011
Posts: 553
Well, they do their job. Not much more to it, but whether it's worth it depends on how much you can stuff. There's a convenience factor involved, I guess. Not sure how you're canning in a wash tub over fire but if it works then there's no real difference, canning is canning. The end product is the same. After canning several jars of marinara sauce, I can't see it being any easier using a pressure canner, and if the end product is safe and pasteurized then that's all that really matters.
__________________

__________________
no mayonnaise is offline   Reply With Quote
Old 04-11-2013, 06:42 AM   #3
Senior Cook
 
GA Home Cook's Avatar
 
Join Date: Sep 2012
Location: Cartersville, GA
Posts: 469
Actually there is quite a bit of difference. Water bath canning, as you described, heats the jar and its contents to 212 degrees F. This is the maximum temperature as water boils at 212 at atmospheric pressure. When pressure canning is done, the jar and its contents are subjected to higher heat because the actual heat is steam and not the water itself. As an example, if the pressure canner is set at 10 psi, the heat of the steam is approximately 240 degrees F. When you can low acid items, such as something that contains meat, you need the higher temperatures to assure that you can kill any bacteria that can cause spoilage. Water batch canners are good for many things, such as jellies, tomatoes and green beans. But you should do some research if you are planning on canning something like Beef Stew.
__________________
GA Home Cook is offline   Reply With Quote
Old 04-11-2013, 08:11 AM   #4
Master Chef
 
Chief Longwind Of The North's Avatar
 
Join Date: Aug 2004
Location: USA,Michigan
Posts: 9,229
I sometimes assist one of our food specialists in the tribe I belong to. Pressure canning is used for any foods that don't have a high acid content. most fruits, and tomatoes have a sufficiently high enough PH that a water bath is sufficient for canning. Microorganisms that can cause spoilage are killed by the combination of acidity and heat.

Food with low acid content, including low acid tomatoes require a pressure canner. Where I live (the Great lakes region) our elevation requires us to bring the pressure canner up to 11.5 pounds to reach a safe temperature for canning. And to set the record straight, water boils at 112' F. at sea level. This temperature is sufficient to destroy molds and organisms that cause food to spoil, as long as there is sufficient acididty. As the air pressure increases, the water has to reach higher temperatures to come to a boil. Under 11.5 pounds of pressure, the water will reach 240'F before it boils, the temperature required to kill nasty, heat resistant spores. It is the higher temperature water, not the steam, that heats the jar and food to a safe temperature. Here is a link that explains it more fully - Canning Temperatures and Processing Times - How To Cooking Tips - RecipeTips.com. It demonstrates that the lower temperature of a boiling water bath won't destroy the most dangerous of the spores, the ones that cause botulism poisoning. And just so you know, the toxin produced by that spore is among the deadliest of all toxins.

So, if you are going to can high acid foods, use your boiling water bath. If you are going to can veggies like green beans, beets, carrots, spinach, or any kind of proteins, you must use a pressure canner.

Seeeeeeya; Chief Longwind of the North
__________________
“No amount of success outside the home can compensate for failure within the home…"

Check out my blog for the friendliest cooking instruction on the net. Go ahead. You know you want to.- http://gwnorthsfamilycookin.wordpress.com/
Chief Longwind Of The North is offline   Reply With Quote
Old 04-11-2013, 03:48 PM   #5
Senior Cook
 
GA Home Cook's Avatar
 
Join Date: Sep 2012
Location: Cartersville, GA
Posts: 469
Chief - Sorry to recorrect, but my degree is in Chemistry.

From chemistry.com

Question: What Temperature Does Water Boil?
At what temperature does water boil? What determines the boiling point of water? Here's the answer to this common question.
Answer: Short Answer: The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level).
__________________
GA Home Cook is offline   Reply With Quote
Old 04-11-2013, 07:16 PM   #6
Head Chef
 
mcnerd's Avatar
 
Join Date: Oct 2007
Location: Southern California
Posts: 1,326
The "pro's" of pressure canning is for one reason only....to kill the C. Botulinum spore which is not killed at temperatures of 212°F. If present and not killed it loves to grow in vacuum stored low-acid foods (meats, vegetables).

The "con's" of pressure canning is that it can turn many foods completely to mush so its not desirable unless necessary and then kept to a tested minimum time that is safe.
__________________
Support bacteria. It's the only culture some people have.
mcnerd is offline   Reply With Quote
Old 04-12-2013, 01:03 AM   #7
Assistant Cook
 
Join Date: Apr 2013
Location: South Texas
Posts: 8
wow thank you all. that answered my question exactly.
__________________
The most important thing we can do to save cats and dogs from all the suffering and death that their overpopulation causes is to spay and neuter them
nana9 is offline   Reply With Quote
Old 04-12-2013, 08:36 AM   #8
Master Chef
 
Chief Longwind Of The North's Avatar
 
Join Date: Aug 2004
Location: USA,Michigan
Posts: 9,229
Quote:
Originally Posted by GA Home Cook View Post
Chief - Sorry to recorrect, but my degree is in Chemistry.

From chemistry.com

Question: What Temperature Does Water Boil?
At what temperature does water boil? What determines the boiling point of water? Here's the answer to this common question.
Answer: Short Answer: The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level).
Yes, and my degree is in Electrical Engineering Technology, and yes, I had to take two classes of physics. You are correct in your assertation that water boils at 100' C at 1 atmosphere. But when the air pressure increases, the water has to be hotter to boil. Water boils when the vapor pressure exceeds the atmospheric pressure. Please see the following site for the formula - Water Vapor Pressure Boiling Point Equations Formulas Calculator. In a pressure cooker, as temperature increases, the atmospheric pressure increases within the vessel. Therefore, more thermal energy is required to create enough vapor pressure to overcome the internal pressure of the air pressure. Hence, the water has to reach a higher temperature to boil. The same is true that as atmospheric pressure decreases, the boiling temperature is reduced. This is what creates gas embolisms in scuba divers. Under greater than 1 atmosphere conditions, the regulators on the the tanks increases the air pressure to compensate for the water pressure on the body. Under the greater pressure, the body fluids absorb more nitrogen from the air tank. If they ascend too quickly, the reduced water pressure causes the vapor pressure in their body fluids to exceed the pressure on their bodies, and gasses boil out, causing havoc. Another way to see this in action is to take a hypodermic needle, and immerse it into plain water. Quickly draw the plunger toward the tube end, creating a partial vacuum. Again, the lower pressure will decrease the atmospheric pressure with relation to the fluid's vapor pressure, and the water boils.

Water does get hotter in a pressure cooker. I also know that if my food is completely immersed in liquid, in the pressure cooker, then it is not subject to the steam, and is cooked entirely by the heat transfer from the water into the food. It still cooks much faster than in boiling water, and food particles break down to make the food more tender.

I have been in environments were super-heated steam was used (I worked on an aircraft carrier. Water vapor can reach temperatures in excess of 1000 ' F., while water will eventually reach a critical temperature and turn to vapor, no matter the atmospheric pressure. That super-heated steam will create enough pressure to launch an airplane, or jet. My pressure cooker is rated for 11.5 lbs. above 1 atmosphere, or about 30 psi., which will raise the boiling point to - about 150' F. at my elevation. According to this table - Pressure and Boiling Points of Water, the boiling point of water at 11 lbs. of pressure is 250'F. at sea level.

So, the pressure cooker does indeed cause an increase in the water temperature inside the vessel before it will boil, thereby cooking the food more quickly, while the pressure breaks down food substances.

Seeeeeya; Chief Longwind of the North
__________________

__________________
“No amount of success outside the home can compensate for failure within the home…"

Check out my blog for the friendliest cooking instruction on the net. Go ahead. You know you want to.- http://gwnorthsfamilycookin.wordpress.com/
Chief Longwind Of The North is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Discuss Cooking on Facebook

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 05:49 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.