Nearly half of the U.S. peanut crop was used to make peanut butter in 2001. Runner peanuts are preferred for peanut butter because they are very uniform in size, which is important to achieve evenly roasted peanuts for the best tasting peanut butter. Runner peanuts are grown primarily in Georgia, Alabama and Florida. These three states accounted for 60% of the U.S. crop in 2001.
Peanuts are planted after the last frost in April, when soil temperatures reach 65 to 70 degrees F. The shelled peanut itself also is the seed. Specially grown and treated peanut kernels from the previous year's crop are planted two inches deep, approximately one to two inches apart in rows.
Peanut seeds crack the soil about 10 days after planting and grow into a green oval-leafed plant about 18 inches tall. The peanut plant is unusual because it flowers above the ground, but fruits below the ground. Delicate yellow flowers form on the plant about 40 days after planting. The flowers pollinate themselves, then the petals fall off as the peanut ovary begins to form. This budding ovary, called a 'peg,' grows away from the plant on a vine and penetrates the soil. The peanuts mature below the ground.
Peanuts are harvested 120 to 160 days after planting, usually in September and October. Harvesting is a rapid process. When the soil is not too wet or too dry (both conditions leave the peanuts stuck in the ground as the plant is pulled free), the farmer drives a tractor with a digger-shaker attachment along the rows of peanuts. The digger has long blades that run four to six inches under the ground loosening the plant and cutting the tap root. Just behind the blade, a shaker lifts the plant from the ground, gently shakes the soil from the peanuts and lays the plant upside-down in windows to dry in the sun for two to three days.
The farmer then drives a combine over the windows to pick the peanuts from the vines. The peanuts are collected in a hopper and the plants are laid back on the ground. The plants can be baled for cattle feed or mulched into the field. The peanuts are dumped into peanut wagons which can be attached to forced air dryers to further dry the peanuts to 10% moisture for storage.
The peanut wagons are taken to buying stations where they are weighed, graded and inspected by the Federal-State Inspection Service to determine the quality and value of the load.
There are 16,000 peanut farmers in nine primary states in the U.S. Peanut farms are mostly operated by family farmers who grow an average of 98 acres of peanuts each year on a 3-year rotation, usually with cotton, corn, soybeans and grass crops. Farmers sold their peanuts in the domestic market for about 30.5¢ a pound in 2001.
From the buying station, the peanuts travel to shelling plants. The peanuts are passed over a series of screens which separate any farm materials such as sticks and rocks from the peanuts and then separate the peanuts by size.
The peanuts are shelled and then inspected by a laser beam and by people to eliminate any immature kernels. The sheller then packs the peanuts into bags, boxes or railcars for delivery to product manufacturers.
The peanut butter manufacturers inspect the peanuts to ensure high quality then roast them in special ovens which provide an even roast. After roasting, the peanuts are fast-cooled by suction fans that circulate air quickly. Rapid cooling is necessary to halt the cooking process, retain an even color and prevent the loss of too much oil.
Another machine rubs the peanuts gently between rubber belts to remove the outer skin -- this is called blanching. The kernels are split, the hearts removed and the peanuts are cleaned and sorted a final time.
Finally, the peanuts are ground in two stages (one long grinding would produce too much heat, damaging the flavor of the peanut butter). In the first stage, the peanuts are ground alone. In the second stage, salt, sweetener and stabilizer (to keep the oil from separating) are added.
Peanut butter today is remarkably like that made 100 years ago. It contains, by law, a minimum of 90% peanuts, with no artificial sweeteners, colors or preservatives. Some brands add about 7% natural sweeteners and 1% salt for taste, plus a stabilizer to keep the peanut butter fresh and the oil from separating. "Old-fashioned" or "natural" peanut butter does not have the stabilizer so the oil will separate and should be stirred back in before using. Peanut butter does not need to be refrigerated.
"Peanut butter spreads," a relatively new category now allowed by FDA, contain only 60% peanuts, but are nutritionally equivalent to peanut butter (although they may contain more sugar or salt). However, many companies have introduced spreads that contain at least 90% peanuts and are still 25% reduced-fat.