Canning novelty. Early methods of manufacture employed poisonous lead solder for sealing the cans. Studies in the 1980s attributed the lead from the cans as a factor in the disastrous outcome of the 1845 Franklin expedition to chart and navigate the Northwest Passage. Later studies found this to be false. Increasing mechanization of the canning process, coupled with a huge increase in urban populations across Europe, resulted in a rising demand for canned food. A number of inventions and improvements followed, and by the 1860s smaller machine-made steel cans were possible, and the time to cook food in sealed cans had
Cat food ingredients, such as heat-sensitive vitamins, which would be destroyed in the extrusion process, may be added. Dry food is most often packed in multi-wall paper bags, sometimes with a plastic film layer; similar bag styles with film laminates or coextrusions are also used. In the United States, canned or wet food (75–78% moisture) generally comes in aluminum or steel cans in 3 oz (85 g), 5.5 oz (156 g), and 13 oz (369 g) sizes. It is also sold in foil pouch form. Even though cats are obligate carnivores, there are vegetarian and vegan cat foods available. Vegetarian cat food