Peanut butter is a popular food used in sandwiches, main dishes and desserts. The peanut originated in South America, between Bolivia and Argentina. Natives grew the plant in pre-Colombian times, and it has been cultivated since. George Washington Carver was key in developing peanut butter in the late 1800s.
The pasteurization process takes place after the peanuts are shelled, stored in a cool area, blanched to remove skins, ground, and mixed. The process takes place under pressure to ensure consistency. The peanut butter is then packaged and pasteurized in hot water. Standard procedure is a 20-minute hot water bath between 158 and 167 degrees.
Pasteurization kills bacteria that may be present in the peanuts. If done properly, does not alter the peanut butter in any way. Pasteurization is done on most peanut butters, with the exception of some "natural" products, which rely on high roasting temperatures and strict cleanliness in processing plants.
After a salmonella outbreak in 2006 and 2007 was linked to peanut butter, researchers did a great deal of study on peanut butter pasteurizing. They found that salmonella can and do survive the normal pasteurization process, and that longer pasteurizing not only discolors peanut butter, but may still miss some bacteria. Some advocate irradiation treatments as an alternative.