During these days of omnipotence of plastics which have invaded practically every facets of human life, the ancient process of canning is almost forgotten. Probably completion of two centuries since canning was invented in France, should evoke some memories of this wonderful technology which once served the admirable purpose of saving millions of tons of foods which otherwise would have gone waste. It is not that the 200 years old technology remained stagnant without any improvement over the years but its importance has been overwhelmingly diluted by other newer technologies due to many factors such as cost, convenience, ease of operation and logistics of waste disposal. All said and done canning technology is still a force to reckon with and cannot be wished away so easily. The progress of canning technology is reflected by the fact that more than 1500 different types of canned foods are made by the industry to day using metal cans and heat stable plastics of 600 different sizes and styles.
Looking back, history's most celebrated confectioner, Nicolas Francois Appert of France who is credited by many with the discovery of preservation of foods by packing in glass jars in the year 1810 or Peter Durand of Great Britain who pioneered the use of metal cannisters (the term can probably was derived from this) for packing in stead of glass jars could have imagined that this technology would lay the foundation of the modern food industry as seen to day. Credit also is due to the reputed French newspaper which offered 12000 francs to any one who invented a process that could preserve food in large quantities which was incidentally won by Nicolas Appert for his sealed glass jar process. As scientific inventions take time to mature, canning technology also made slow progress till 1940s and became a moder technology of choice in many countries. Early ears of using cylindrical tin cans or wrought-iron cannisters cannot be forgotten as they served the humanity well. It is hard to believe that during early stages of canned foods, there was not even a reliable and convenient tool to open the sealed cans before consumption of the contents. It was only in 1858 the can opener device was invented that made life easy for the consumers. It took more than 50 years for the process to become amenable to easy operation when average heating time came down dramatically from 6 hours to just 30 minutes. Modern day sanitary cans are designed sturdily with double seam closure mechanism, tin-free steel construction and welding of the body seam in place of the traditional lead containing solders. Flip open cans used commonly in beverage packing are made of aluminum with easy to open mechanism.
Many credit Louis Pasteur with the discovery of the science behind canning through his findings that microorganisms are responsible for food spoilage and heat can destroy such spoilage organisms and disease causing microbes. While canning is offered referred to as "Appertization" in honor of Nicolas Appert, the process of killing pathogenic microorganism through heat is called "Pasteurization" in memory of the great scientist-microbiologist Louis Pasteur. It is another story that the industry has been able to graduate into more efficient technologies like sterilization and aseptic packing which are the leading processes that preserve the quality and ensure safety of majority of foods in to day's market. With just simple pasteurization mankind would not have been able to deal with deadly bacteria like Clostridium bottulinum, notorious for its bottulism toxicity. The spores of this bacteria can survive at 100C for more than 300 minutes and resurface in the under favorable conditions. Use of pH manipulation to bring down the pH to less than 4.6 has still make it possible to achieve sterilization of liquid foods packed in cans using boiling water temperature. High Temperature Short Time process which is widely used to day is designed to take the temperature to levels as high as 135C when all microorganisms perish within a few seconds. Computation of Thermal Death Time (TDT) for typical pathogens and accurate estimation of processing time and temperature to achieve desired log reduction have made canning one of the safest processes with no chance of compromises on food safety.