Canners and home canning methods that are unsafe and NOT recommended for home
People occasionally ask, "why use a water bath method or a
pressure canner?" adding:
"my grandmother just filled the jars with hot fruit,
vegetables or jam then just sealed and inverted the jars"; or
"I have a steam canner that my grandmother used and she never
got ill!" or
My family just uses a water bath canner to can vegetables
like beans and corn. What's wrong with that?" or
"We use the oven to heat the filled jars, it gets plenty hot
and the jars seal" or
"Why can't I just use the microwave to blanch or heat the
food then quickly seal the jars?" or even
I've used the dishwasher to process the filled jars and
that's always worked fine for me!"
As preposterous as the "dishwasher method" may seem, all of
these methods are unsafe. And it may be true, that no one in their family has
died (yet) from their canned food, just as there are occasionally smokers who live to
100 or children who play in the street and don't get hit by a car, it's hardly
something a rational person does (yes, for the record, I AM saying that smokers
are behaving irrationally or are in addicted denial) . Botulism food
poisoning is nothing to mess with! See this
page for detailed information about botulism food poisoning.
Now, for those of you non-smokers who are still reading (the
smokers are now busy writing me hate mail, or by now need a nicotine break, so
they've gone outside); here are detailed explanations and references from
Open Kettle Canning (aka, inversion canning)
The open-kettle method means placing hot food in jars and sealing with no
further heat treatment. This is the method that many grandma's used in which granny fills a jar (sanitized or not)
with hot fruit, pickles, etc., puts the lid and ring on, then turns it
upside down. The jar will cool and seal, BUT it is NOT sterile, as the
contents were exposed to the air (and airborne bacteria) just before
sealing. From the moment the jars were filled, the contents started cooling, so airborne
bacteria contacting the cooling surfaces will still be viable. They were not exposed to a heat high enough, nor long enough to destroy
them. Then granny gives the jars away, playing Russian Roulette.
Maybe you'll get sick, maybe not. Again, this method is NOT recommended for home canning because
the amount of heat applied may not be sufficient to destroy bacteria and the
product may spoil quickly or cause illness when consumed.
The USDA and many, many universities have warnings against the use of this
method (see the bottom of this page for references). Here's a typical
statement, from the University of Georgia:
"An old out-dated method of canning – the open-kettle method – is now
considered unsafe. In this method, foods were heated in a kettle, then
poured into jars, and a lid was placed on the jar. No processing was
done. With this method there was often spoilage, because bacteria,
yeasts, and molds that contaminated the food when the jars were filled
were not killed by further processing. The growth of these
microorganisms, in addition to spoiling the food, often caused lids that
did seal to later come unsealed. This method resulted in a very real
danger of botulism."
Steam Canners The steam canner was designed as a means to process foods using
steam without the aid of pressure. The manufacturer claims this process uses
less water, saves time and energy, and recommends identical processing times as
those required for boiling-water bath treatments.
According to the National Home Food Preservation Center (USDA / U.Ga.):
"Steam canning is not recommended at this time for either acid or low
acid foods. Processing times for use with current models have not been
adequately researched. Today's steam canner looks like an upside-down
boiling water canner. The base is a shallow pan with a rack that is
covered with a high dome lid. After the jars of foods are placed on the
canner's base, a small amount of water in the base is brought to a boil
and the dome fills with steam. The jars and foods in them are heated by
the steam surrounding them. However, steam canners do not heat foods in
jars exactly the same as boiling water canning does. Low acid foods are
potentially deadly because Clostridium botulinum bacteria could survive
the steam canning and produce the poison that causes botulism. Acid
foods may also be underprocessed and therefore could spoil."
concluded that: -
canners result in significantly lower product temperatures at the beginning
and end of the scheduled process when compared to water-bath canning.
Use of steam canners
as instructed by the manufacturer would result in under processing and
considerable economic spoilage.
- Because steam canners may not heat foods in the same manner as boiling
water canners, using boiling-water process times with steam canners may
result in spoilage. There is no tested nor approved conversion factor.
Micro-Dome Food Preserver -
Micro-Dome Food Preserver Recalled Washington, DC--The U.S. Consumer Product
Safety Commission (CPSC) in cooperation with Micro-Dome of San Ramon, CA, has
warned consumers of certain safety hazards associated with the use of the
"Micro-Dome Food Preserver" manufactured by Micro-Dome and sold and distributed
to consumers after August 1987. The CPSC has also urged consumers to destroy all
food that has been preserved using a Micro-Dome Food Preserver
Solar Canning The heat generated from captured
sunlight is not a reliable method to process acid foods and should never be used
to can low-acid foods.
Oven Canning Oven-canning is extremely
hazardous. The oven canning method involves placing jars in an oven and heating.
In oven canning, product temperatures never exceed the boiling point, and
uniform heat penetration cannot be assured. It is, therefore, not considered safe to use for
process fails to destroy the many bacteria, including the spores of Clostridium botulinum, it can cause the
food to become toxic during storage. Also, canning jars are not designed for
intense dry heat and may explode resulting in serious cuts or burns. Of
the USDA says:
"This also is not 'canning'. There is not sufficient, research-based
documentation to support that 'canning' any food in a dry oven as described
on this web page or any page that proposes oven canning is even sufficient
heating to destroy bacteria of concern, let alone enough to produce a proper
seal with today's home canning lids. "
Microwave oven cannot be used for home canning. Microwaved food reaches 212 F
but heating is not uniform. There is also a danger of explosion of the jars
within the microwave oven or as food is being removed from the oven.
Processing canned foods in a dishwater cycle is dangerous. The temperature of
the water during the cleaning and rinsing cycle is far below that required to
kill harmful microorganisms. Thus the product will be underprocessed and unsafe
to eat. Note that it is fine to use the dishwasher to clean and sanitize
the empty jars, especially if your dishwasher has a "sanitize" setting -
the empty jars will get hot enough.
Aspirin / Salicylic acid - So-called canning powders are
useless as preservatives and do not replace the need for proper heat
processing. You may have heard of someone's
grandmother canning corn by boiling the corn, adding aspirin or salicylic
acid from the drugstore, then sealing the corn in jars with no further
processing. According to the
University of Illinois, a recipe circulated several years ago, using
aspirin to acidify tomatoes and beans for canning. Aspirin is not
recommended for canning. While it contains salicylic acid, it does not
sufficiently acidify low acid foods like tomatoes or beans for safe hot
water bath canning. Low acid foods (without added acids) should only be
processed safely in a pressure canner. Lemon juice or vinegar is recommended
to acidify tomato products for safe water bath processing. You can also see
article in JAMA (the Journal of the American Medical Association, Vol. 289
No. 13, April 2, 2003, titled "Is salicylic acid as a food preservative
harmful?"; from which the abstract states: "salicylic acid, inthe ways in which it is used in the preparation of food products,is not only not harmful, but is a preservative to health, inasmuchas the process of decomposition which it prevents would be farmore dangerous."
Using Paraffin or other wax to seal jars, like jams, preserves and
jellies: This is an outdated
method from 50 years or more ago, that is considered unsafe. The lid and
ring method with a boiling water bath (usually on 5 minutes for jams and
jellies) is much safer. The USDA says:
“Because of possible mold contamination, paraffin or wax
seals are no longer recommended for. any sweet spread, including jellies.”
The University of Minnesota’s Extension says:
“Note. Jelly jars and paraffin are no longer
recommended. An incomplete seal with paraffin and the absence of a heat
treatment may result in mold growth and toxin production in the jelly.
Persons continuing to use the paraffin / no water bath method should be
aware of the potential health risk.”
This is just a small sampling of the many authorities who concur that the only
safe home canning methods are the water bath canner (for jams and acidic fruits
and vegetables) and the pressure canner (for low acid fruits and vegetables,
meats, and dairy). Click on the links to see their articles.
For more information, and NO obligation to buy, just click on
the links in the Amazon boxes on the left!
If you want to can low-acid foods such as red meats, sea food, poultry,
milk, and all fresh vegetables with the exception of most tomatoes,
you will need a pressure canner. These foods fit into the
low acid group since they have an acidity, or pH level, of 4.6 or
greater. The temperature which must be reached and maintained (for a
specified amount of time) to kill the bacteria is 240 F. Pressure canning is the only canning method recommended safe by
the U.S.D.A. for low-acid foods such as vegetables, meats, and fish. Ordinary water
bath canners can only reach 212 F and can not to kill the types of
bacteria that will grow in low acid foods. This temperature can be
reached only by creating steam under pressure as achieved in quality
There are several manufacturers of pressure canners. The two
leading ones are Presto and All American (Wisconsin Aluminum). They are more expensive
than water bath canners, but extremely well built - I bought
mine in 1988 and it still looks and works like new!
Presto 01781 23-Quart Pressure Cooker/Canner
This is usually about $80 PLUS SHIPPING.
(which is a GREAT price for a pressure canner). There is also a 16
quart version for about $69. Click on the links
at left or above for more info and current pricing. It is also available
from Amazon .com (click on the box link at left) (and below from Target)
17 by 15-1/2 inches; 12-year warranty
Heavy-duty 23-quart aluminum pressure canner and
Comfortably ergonomic, stay-cool black plastic
Strong-lock lid with pressure regulator, dial
gauge, and overpressure plug
Comes with canning rack to protect jars during