In 1956, Nelson and Seinberg of the University of Illinois experimented with several films, including polyester film.
From 1958 onwards, the U.S. Army Natick Laboratory and Swift Laboratory began research on retort pouches for military use, conducting extensive trials and performance tests to replace tin cans used on the battlefield with retort pouches. In 1969, the retort pouches developed by the Natick Laboratory were successfully used in the Apollo space program.
Because this type of packaged food can be stored at room temperature and has a long shelf life, can be eaten both hot and cold, is convenient, and saves energy required for preservation, it is very popular. Sweden was the first country in the world to produce and sell retort pouches; however, Japan is the world leader in the large-scale commercial production of retort pouches. In 1968, Otsuka Foods Co., Ltd. in Japan used transparent high-temperature retort pouches to package curry products, achieving the first commercialization in Japan. In 1969, aluminum foil was used as the raw material to improve the quality of the bags, leading to a continuous expansion of market sales. In 1970, production of rice products packaged in retort pouches began. In 1972, hamburger patties packaged in retort pouches were developed and commercialized, and meatballs packaged in retort pouches were also introduced to the market. The earliest aluminum foil retort pouches were made of three layers of heat-resistant composite material and were called "retort pouches" (RP). The retort pouches sold by Toyo Cans Corporation of Japan, containing aluminum foil, were called RP-F (resistant to 135℃), while the transparent multi-layer composite bags without aluminum foil were called RP-T and RR-N (resistant to 120℃). In Europe and America, these bags are called flexible cans or soft cans.
