Heating differentiates pecan allergen stability: Car i 4 is more heat labile than Car i 1 and Car i 2

Authors: Brown, Chaka; Dupre, Rebecca; EBMEIER, CHRISTOPHER - University Of Colorado; Patil, Shaina; Smith, Brennan; Mattison, Christopher

Submitted to: Food Science and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2024
Publication Date: 2/16/2025
Citation: Brown, C.N., Dupre, R.A., Ebmeier, C.C., Patil, S.L., Smith, B., Mattison, C.P. 2025. Heating differentiates pecan allergen stability: Car i 4 is more heat labile than Car i 1 and Car i 2. Food Science and Nutrition. https://doi.org/10.1002/fsn3.4747.

Interpretive Summary: Pecan nuts can be eaten raw, toasted, or incorporated into baked goods. While they are delicious and nutritious, pecans contain three proteins, called Car i 1, Car i 2, and Car i 4, that commonly act as allergens. Heating can alter the ability of these allergens to cause a reaction by altering their solubility or shape. The changes in pecan allergen solubility and shape in response to heat were evaluated using several molecular methods. Whole pecans from three different grocery stores were roasted for up to 24 minutes in an oven at 300 degrees Fahrenheit. Imaging of the heated pecan proteins revealed that relatively smaller proteins, including the Car i 1 allergen, remained soluble even after 24 minutes of heating. However, the solubility of higher molecular mass proteins such as Car i 2 and Car i 4 decreased after 20 and 24 minutes of heating. Even so, a sensitive method called mass-spectrometry revealed that small fragments of Car i 2 and Car i 4, called peptides, that remained soluble were generated during heating. Analysis of the data generated by this research provided a set of peptides that can be used for the reliable detection of Car i 1, Car i 2, and Car i 4, in both heated and unheated samples. This list of peptides is useful for food processing and quality testing labs to follow pecan content in foods.

Technical Abstract: Pecans are a staple in American cuisine and may be eaten raw but are often roasted or baked. Heating can alter pecan protein content and pecan allergen solubility. Three seed storage proteins (Car i 1, Car i 2, and Car i 4) commonly act as allergens and are recognized by IgE from pecan allergic individuals. Time resolved changes in the solubility of pecan allergens in response to heat were assessed by SDS-PAGE, immunoblot, and mass-spectrometry. Whole pecans from three different commercial sources were roasted for up to 24 minutes in an oven at 300 'F. Relatively smaller proteins such as Car i 1 remained soluble even after 24 minutes of heating and were stably observed by SDS-PAGE, immunoblot, and mass-spectrometry. However, the solubility of higher molecular mass proteins such as Car i 2 and Car i 4 decreased after 20 and 24 minutes of heating as reflected in SDS-PAGE and decreased antibody binding on immunoblot. Nonetheless, mass-spectrometric peptide characterization indicated that Car i 2 peptides remained relatively stable throughout heating. In contrast, Car i 4 was relatively more sensitive to heating and produced relatively fewer heating-insensitive peptides. A set of heat-resistant peptides for the reliable detection of three pecan allergens, Car i 1, Car i 2, and Car i 4, were identified.