pine nut

Shelled European pine nuts (Pinus pinea)

Shelled Korean pine nuts (Pinus koraiensis)

Stone Pine cone with pine nuts — note two nuts under each cone scale

Pine nuts are the edible seeds of pines (family Pinaceae, genus Pinus). About 20 species of pine produce seeds large enough to be worth harvesting; in other pines the seeds are also edible, but are too small to be of great value as a human food.^[1][2][3]

Species and geographic spread

In Asia, two species are widely harvested, Korean Pine (Pinus koraiensis) in northeast Asia (the most important species in international trade), and Chilgoza Pine (Pinus gerardiana) in the western Himalaya. Four other species, Siberian Pine (Pinus sibirica), Siberian Dwarf Pine (Pinus pumila), Chinese White Pine (Pinus armandii) and Lacebark Pine (Pinus bungeana), are also used to a lesser extent. Afghanistan is an important source of pine nuts.

Pine nuts produced in Europe mostly come from the Stone Pine (Pinus pinea), which has been cultivated for its nuts for over 6,000 years, and harvested from wild trees for far longer. The Swiss Pine (Pinus cembra) is also used to a very small extent.

In North America, the main species are three of the pinyon pines, Colorado Pinyon (Pinus edulis), Single-leaf Pinyon (Pinus monophylla), and Mexican Pinyon (Pinus cembroides). The other eight pinyon species are used to a small extent, as are Gray Pine (Pinus sabineana), Torrey Pine (Pinus torreyana), Sugar Pine (Pinus lambertiana) and Parry Pinyon (Pinus quadrifolia).

In the United States, pine nuts are mainly harvested by Native Americans, particularly the Uto-Aztecan: Shoshone, Paiute and Hopi, and Washoe tribes.^[4] Certain treaties negotiated by tribes and laws in Nevada guarantee Native Americans' right to harvest pine nuts.^[5]

Pollination and seed development

The pinyon pine nut (seed) species will take 18 months to complete its maturity; however, to reach full maturity, the environmental conditions must be favorable for the tree and its cone.

Development begins in early spring with pollination. A tiny cone, about the size of a small marble, will form from mid-spring to the end of summer; the premature cone will then become and remain dormant (with a cessation of growth) until the following spring. The cone will then commence growth until it reaches maturity near the end of summer.^[6] The mature pinyon pine cone is ready to harvest ten days before the green cone begins to open. A cone is harvested by placing it in a burlap bag and exposing it to a heat source such as the sun to begin the drying process. It takes about 20 days until the cone fully opens. Once it is fully open and dry, the seed can be easily extracted in various ways. The most common and practical extracting method used is the repeated striking of the burlap bag containing the cone(s) against a rough surface to cause the cone(s) to shatter, leaving just the job of separating by hand the seed from the residue within the bag.

Another option for harvesting is to wait until the cone opens on the tree (as it naturally will) and harvest the cone from the pinyon pine, followed by the extracting process mentioned above. Fallen seed can also be gathered beneath the trees.^[7]

Ecology and status

In the United States, millions of hectares of productive pinyon pine woods have been destroyed due to conversion of lands, and in China, destructive harvesting techniques (such as breaking off whole branches to harvest the cones) and the removal of trees for timber have led to losses in production capacity.^[2]

Elevation and pinecone production

European Stone Pine nuts (Pinus pinea) to be compared with the picture below

Korean Pine (Pinus koraiensis) pine nuts - unshelled, and shell, above; shelled, below

The elevation of the pinyon pine is an important determinant of the quantity of pine cone production, and therefore, will largely determine the amount of pine nuts the tree will yield.^[8]

Pinyon pine cone production is most commonly found at an elevation between 6,000 feet (1,800 m) and 8,500 feet (2,600 m), and ideally at 7,000 feet (2,100 m). This is due to increased temperatures at elevations lower than 6,000 feet (1,800 m) during the spring, will dry up humidity and moisture contents (particularly snow packs) that provide for the tree throughout the spring and summer, causing little nourishment for pine cone maturity. Although there are several other environmental factors, such as clouds and rain, that determine the conditions of the ecology, without this nourishment (water), the cones are more susceptible to perishing and the tree will tend to abort cones.

There are certain topographical areas found in lower elevations, such as shaded canyons, where the humidity remains constant throughout the spring and summer, allowing the pine cones to fully mature and produce seed.

At elevations above 8,500 feet (2,600 m), the temperature will substantially drop, drastically affecting the state of the dormant cone. During the winter, the change in temperature, along with gusty winds, with their severity, can cause the cones to be susceptible to freezing that damages them permanently, in which case, growth is stunted and they wither away.^[9]

Physical characteristics

Pine nuts contain, depending on species, 10–34% protein, with Stone Pine having the highest content.^[2] They are also a source of dietary fiber. When first extracted from the pine cone, they are covered with a hard shell (seed coat), thin in some species, thick in others. The nutrition is stored in the embryo (sporophyte) in the centre. Although a nut in the culinary sense, in the botanical sense pine nuts are seeds; being a gymnosperm, they lack a carpel (fruit) outside.

The shell must be removed before the pine nut can be eaten. Unshelled pine nuts have a long shelf life if kept dry and refrigerated (−5 °C (23 °F) to 2 °C (36 °F)); shelled nuts (and unshelled nuts in warm conditions) deteriorate rapidly, becoming rancid within a few weeks or even days in warm humid conditions. Pine nuts are commercially available in shelled form, but due to poor storage, can have poor flavour and may be already rancid at the time of purchase. Consequently, pine nuts are often frozen to preserve their flavour.

Pinon nuts (Pinus edulis) packed for shipment, Santa Fe, New Mexico, 1921.

European pine nuts may be distinguished from Asian ones by their greater length in comparison to girth; Asian pine nuts are stubbier, shaped somewhat like long kernels of corn. The American pinyon nuts are known for their large size and ease of shelling. In the United States, P. edulis, the hard shell or New Mexico and Colorado, became a sought-after species due to the Trading Post System and the Navajo people who used the nuts as a means of commerce. The Italian pine nut, (P. pinea) was brought to the United States by immigrants, and became a favored treat along the East Coast until the early 1930s, when bumper crops of American pine nuts were readily available at low prices.

Culinary uses

Pine nuts have been eaten in Europe and Asia since the Paleolithic period. They are frequently added to meat, fish, salads and vegetable dishes or baked into bread. In Italian they are called pignoli (in the U.S. they are often called "pinoli" but in Italy "pignolo" is actually a word far more commonly used to describe a fussy, overly fastidious or extremely meticulous person)^[10] and are an essential component of Italian pesto sauce. Pignoli cookies, an Italian American specialty confection (in Italy these would be called "biscotti ai pinoli"), are made of almond flour formed into a dough similar to that of a macaroon and then topped with pine nuts. In Spain, a sweet is made of small marzipan balls covered with pine nuts, painted with egg and lightly cooked. Pine nuts are also featured in the salade landaise of southwestern France. Pine nut coffee, known as piñón (Spanish for pine nut), is a speciality found in the southwest United States, especially New Mexico, and is typically a dark roast coffee having a deep, nutty flavour; roasted and lightly salted pine nuts can often be found sold on the side of the road in cities across New Mexico to be used for this purpose, as well as a snack. The Nevada, or Great Basin, pine nut has a sweet fruity flavor and is relished for its large size, sweet flavor and ease of peeling. Pine nuts are also widely used in Middle Eastern cuisine, reflected in a diverse range of dishes such as kibbeh, sambusek, desserts such as baklava, and many others.

Throughout Europe and Middle East the pine nuts used are from Pinus pinea (Stone Pine)^{[dubious – discuss]}. They are easily distinguished from the Asian pine nuts by their more slender shape and more homogeneous flesh. Due to the lower price, Asian pine nuts are also often used, especially in cheaper preparations. Pine nuts contain thiamine (vitamin B₁) and protein.

Risks from eating pine nuts

Pine nuts can cause taste disturbances, lasting between a few days to a few weeks after consumption. A bitter, metallic taste is described. Though unpleasant, there are no known lasting effects, with the FDA reporting that there are "no apparent adverse clinical side effects."^[11]. This phenomenon was first described in a scientific paper in 2001.^[12] Publications have made reference to this phenomenon as "pine nut syndrome" or as "pine mouth".^[13] The Nestlé Research Centre has hypothesized that nuts from a particular species of pine occurring mostly in China, Pinus armandii, is the cause of the problem. The suspect species of pine nuts are smaller, duller, and more rounded than typical pine nuts.^[14] A 2011 study found results consistent with this hypothesis and also suggested that chemicals used in the shelling process might be responsible.^[15] Metallic taste disturbance, known as metallogeusia, is typically reported 1–3 days after ingestion, being worse on day 2 and lasting typically up to 2 weeks. Cases are self-limited and resolve without treatment.^[16] Möller^[17] has postulated a hypothesis that could explain why the bitter taste appears several days after ingestion and lasts for as long. A well known physiological process known as enterohepatic recirculation (EHR) could play a key role in the development of PNS.

The FDA is currently investigating “Pine Mouth”.^[18]

Nutritional information

100g of dried pine nuts contains:^[19]

• Calories :673
• Carbohydrates(g): 13.08
• Fibers(g): 3.7
• Protein(g): 13.69
• Cholesterol(mg): 0

Pine nut oil

Pine nuts can be pressed to extract pine nut oil, which is valued for its mild, nutty flavour. One study indicates Korean pine nut oil may suppress appetite.^[20]

Other similar seeds

The large edible seeds of species of the Southern Hemisphere conifer genus Araucaria, notably Araucaria araucana (Pehuén) of Chile, Araucaria bidwillii (Bunya) of Australia and Araucaria angustifolia (Parana pine) of Brazil, are also often called, although improperly, pine nuts. In South America, Araucaria seeds are called piñas, pinhas or pinhões.

See also

• List of edible seeds
• Pignolo

References