Some older canning methods sometimes return to fashion and often cause serious health problems. Using them is like playing dice with the health of all people who consume the canned product.
In this method, popular in the mid 20th century, the filled jars are placed in a hot oven to be heat-treated. Unfortunately there is no guarantee that the internal temperature in the jars will reach the desired level and maintain it long enough to ensure destruction of harmful microorganisms. There is also a very real risk of seeing jars explode in the oven when the door is open and fresh air enters suddenly in contact with the hot glass surface of the jars.
This method assumes, incorrectly, that the simple cooking of food is sufficient to eliminate harmful microorganisms. The product is then poured, hot, into sterilized jars and a cover is quickly installed which will seal during cooling of the product. This method is extremely dangerous! The temperature and cooking time are rarely sufficient to ensure the destruction of most harmful components. Even in very hygienic conditions it is impossible to prevent the addition of natural contaminants that are always in the air. They will eventually affect the food and make it unsafe to eat.
The jars are placed in a covered pot, steam is produced by a small amount of water and is used to “warm up” the jars. As opposed to the “pressure canning” method there is no way to ensure good heat distribution and to verify its intensity. It is virtually impossible to actually destroy harmful micro-organisms by this method.
While “technically” feasible, this method of placing the jars in a microwave oven to process, has many problems. As each device uses different emitter and there is no easy way to check the internal temperature of food. It is virtually impossible to achieve a safe result with such a treatment. There is also the fact that microwave ovens are small and therefore can contain only a few jars at a time. Finally the covers, that are usually made of metal, cannot be places in a microwave.
A trend of the 60′s while the dishwasher was becoming popular and manufacturers attributed to it the virtues of a universal instrument. As there is no effective way to check the temperature in the dishwasher and it varies between cycles, this method should be avoided. The dishwasher can be very useful for washing the jars and keep warm before canning.
Canning with “aspirin”
VERY DANGEROUS. The addition of aspirin to food has no effect on micro-organisms and is a guarantee that the product will soon be unfit for consumption.
Canning with “wax or paraffin” seal
The use of wax or paraffin to seal the jars was popular from the late 19th and up to the late 20th century. Unfortunately, this method is similar to “no treatment” canning and does not destroy harmful microorganisms that will eventually affect the food and make them unsafe to eat.