Canning is a method of preserving food over extended periods of time. It involves sealing food in containers and heating it in order to kill bacteria that could eventually cause spoilage. While most canned food is produced by commercial companies, some canning is done at home. Although if can be less hygienic than the commercial variety, home canning is a good way to preserve homegrown fruits and vegetables such as apples and tomatoes. These products can be canned after boiling, but others must be pickled first, cucumbers and peppers for example.