Pine Nuts (Pinus spp.)

Botanical Characteristics of Pine Nuts (Pinus spp.)

• Scientific Name: Pinus spp. (Various species, including Pinus pinea, Pinus koraiensis, Pinus sibirica)
• Family: Pinaceae (Pine family)
• Common Names: Pine nut, Pignoli, Pinyon nut, Piñon
• Native Regions: Mediterranean, Asia, North America

Tree and Seed Description

• Pine nuts are edible seeds harvested from pine tree cones.
• Common species producing pine nuts:
  • Mediterranean pine nut (Pinus pinea) – Used in pesto.
  • Korean pine nut (Pinus koraiensis) – Common in Asian cuisine.
  • Siberian pine nut (Pinus sibirica) – Found in Russia and China.
• Unlike true nuts, pine nuts are seeds, but they are classified as tree nuts for allergenic purposes.

Pine Nut as a Food Allergen

Pine nuts are classified as a major tree nut allergen under U.S. FDA labeling laws due to documented IgE-mediated allergic reactions.

Allergenic Proteins in Pine Nuts

Allergen Name	Protein Family	Molecular Weight (kDa)	Function	Cross-Reactivity
Pin p 1	2S Albumin	~9 kDa	Seed storage protein	Cross-reacts with peanuts, Brazil nuts
Pin p 2	7S Vicilin	~45-50 kDa	Storage protein	Cross-reacts with cashews, almonds
Pin p 3	Lipid Transfer Protein (LTP)	~9 kDa	Transport protein	Linked to peach, apple, cherry allergies
Pin p 4	Profilin	~15 kDa	Actin-binding protein	Cross-reacts with pollen allergens (grass, birch)

Cross-Reactivity

• Similar to tree nuts (walnuts, almonds, cashews) due to shared storage proteins (Vicilin, Albumin).
• Contains LTP allergens, which may cross-react with Rosaceae fruits (peach, apple, cherry).
• Profilin cross-reactivity with pollen allergens may cause mild oral allergy syndrome (OAS).

Epitope Mapping of Pine Nut Allergens

Pine nut allergens contain linear and conformational IgE-binding epitopes.

Pin p 1 (2S Albumin)

• Regions with IgE-binding epitopes:
  • Amino acids: 10–30, 80–100, 140–160
  • Core IgE-binding sites: Cysteine-stabilized domains
• Clinical Significance:
  • Highly stable allergen, causing severe allergic reactions.
  • Cross-reacts with peanuts, Brazil nuts.
  • Resistant to heat and enzymatic breakdown.

Pin p 2 (7S Vicilin)

• Regions with IgE-binding epitopes:
  • Amino acids: 30–50, 100–120, 180–200
  • Core IgE-binding sites: Beta-barrel structures
• Clinical Significance:
  • Common storage protein allergen in tree nuts.
  • Similar to cashew (Ana o 1) and almond proteins.
  • Moderate resistance to digestion.

Pin p 3 (Lipid Transfer Protein – LTP)

• Regions with IgE-binding epitopes:
  • Amino acids: 20–40, 80–100, 130–150
  • Core IgE-binding sites: Hydrophobic lipid-binding regions
• Clinical Significance:
  • Triggers severe reactions in LTP-sensitive individuals.
  • Cross-reacts with peaches, apples, cherries (Rosaceae family).

Pin p 4 (Profilin)

• Regions with IgE-binding epitopes:
  • Amino acids: 30–50, 100–120
  • Core IgE-binding sites: Actin-binding domains
• Clinical Significance:
  • Mild allergen, often linked to Oral Allergy Syndrome (OAS).
  • Cross-reacts with birch pollen, grass pollen.

Stability of Pine Nut Allergens

Allergen	Heat Stability	Gastric Stability	Processing Effect
Pin p 1 (2S Albumin)	High	High	Resistant to roasting
Pin p 2 (7S Vicilin)	Medium	Medium	Partially degraded
Pin p 3 (LTP)	High	High	Stable even in refined oils
Pin p 4 (Profilin)	Low	Low	Destroyed by cooking

• Pine nut allergens like Pin p 1 and Pin p 3 remain stable, meaning roasted pine nuts can still cause reactions.
• Profilins are heat-sensitive and may be reduced in cooked or processed foods.

Symptoms of Pine Nut Allergy

Reactions range from mild to life-threatening.

Mild Symptoms

• Oral Allergy Syndrome (OAS): Itchy mouth, tingling lips.
• Hives, skin rash.
• Nausea, vomiting, diarrhea.

Severe Symptoms (Anaphylaxis)    Epinephrine (EpiPen®) is required for anaphylaxis

• Swelling of throat (laryngeal edema).
• Difficulty breathing, wheezing.
• Drop in blood pressure (anaphylactic shock).

Diagnosis and Testing

Skin Prick Test (SPT)

• Detects IgE-mediated reactions to pine nut extract.

Serum IgE Testing

• Measures IgE antibodies against Pin p 1, Pin p 2, Pin p 3.

Oral Food Challenge (OFC)

• Gold standard for confirming allergy.
• Performed under medical supervision.

Comparison with Other Tree Nuts and Seeds

Nut/Seed	Major Allergen	Cross-Reactivity	Stability	Anaphylaxis Risk
Pine Nut	Pin p 1, Pin p 2, Pin p 3	Cashews, Walnuts, Rosaceae Fruits	High	Moderate
Walnut	Jug r 1, Jug r 2, Jug r 3	Pecans, Almonds, Peanuts	High	High
Hazelnut	Cor a 1, Cor a 9, Cor a 11	Birch Pollen, Tree Nuts	Moderate	Moderate
Peanut	Ara h 1, Ara h 2, Ara h 6	Tree Nuts, Legumes	High	High

• Pine nuts are closer to tree nuts in allergenic potential but are not true nuts.
• LTP-sensitive individuals may react to both pine nuts and Rosaceae fruits.
• Cashew and walnut allergy sufferers should be cautious with pine nuts.

Conclusion

• Pine nuts contain potent allergens (Pin p 1, Pin p 2, Pin p 3) that can trigger IgE-mediated reactions.
• Cross-reactivity with cashews, walnuts, and LTP-containing fruits is common.
• Roasting does not eliminate allergenicity.
• Strict avoidance and emergency preparedness are necessary for severe allergies.