Ara h 1 is no minor player. It makes up 12 to 16 percent of total peanut protein and is recognized by IgE antibodies in 70 to 90 percent of peanut-allergic patients. Of the 19 peanut allergens officially designated by the WHO/IUIS Allergen Nomenclature Sub-Committee, Ara h 1 stands out as a seed storage protein whose three-dimensional shape underpins much of its allergenicity. The research team, led by Yong-Qiang Wang and Ying-Chao Li of Changzhou Vocational Institute of Engineering together with colleagues at Jiangyin People’s Hospital, Yangzhou University and Jiangnan University, set out to test whether high-temperature and high-pressure (HTHP) treatment, essentially the saturated steam conditions of commercial autoclaving and retorting, could reshape that protein enough to blunt its immunoreactivity.

The researchers worked with two systems side by side: purified Ara h 1 and a crude peanut protein extract, so they could compare how the allergen behaves in isolation versus within the complex matrix of a real food. They subjected both to steam treatment at 121 degrees Celsius under 0.1 megapascals of pressure and at 135 degrees Celsius under 0.22 megapascals, for durations ranging from 10 to 60 minutes. These temperatures were chosen deliberately because they correspond to standard commercial sterilization protocols, meaning any findings could translate directly into existing food industry practice rather than requiring novel equipment or processing steps.

The results were striking. After 20 minutes at 135 degrees Celsius, the immunoreactivity of purified Ara h 1 fell to 33.4 percent of the untreated control, and after 60 minutes it dropped to just 16.7 percent. In the crude peanut extract, the effect was even more pronounced: immunoreactivity fell to 25.0 percent and 10.0 percent of control levels after 20 and 60 minutes respectively. The team measured this using competitive ELISA with rabbit polyclonal antibodies raised against the allergen, and confirmed the pattern with Western blotting, which revealed that the intact 65-kilodalton Ara h 1 band progressively disappeared while immunoreactive fragments accumulated at roughly 55, 35, 25 and 15 kilodaltons depending on the treatment and the sample matrix.

Electrophoresis told a story of molecular demolition. Under the harshest conditions, 135 degrees Celsius for 20 minutes or longer, small proteins of 15 kilodaltons or less came to dominate the soluble fraction, constituting approximately 56 to 75 percent of total soluble protein after an hour. Soluble protein content of purified Ara h 1 dropped by about 36 percent after 20 minutes at 135 degrees Celsius before plateauing, suggesting that part of the protein had aggregated into insoluble forms or degraded while the remainder resisted further precipitation. Intriguingly, Ara h 1 appeared less thermally stable within the crude extract than on its own, with the intact 65-kilodalton band vanishing more readily in the mixed protein environment, possibly because interactions with a protein of around 55 kilodaltons promoted its aggregation or altered its degradation pathway.

To see what the treatment actually did to the protein’s architecture, the team turned to atomic force microscopy, circular dichroism spectroscopy and intrinsic fluorescence. Native Ara h 1 appeared under the microscope as uniform spheres roughly 5 nanometers tall. After 20 minutes at 135 degrees Celsius, those spheres had transformed into irregular short rod-like aggregates about 3 nanometers in height, and after an hour at either temperature the protein formed heterogeneous globular fragments only around 2 nanometers tall. The morphology mirrored that of Ara h 1 extracted from roasted peanuts in earlier studies, reinforcing the picture of a protein that refolds into compact, fragmented structures after thermal assault.

The spectroscopic data filled in the molecular details. Circular dichroism in the far-ultraviolet region showed that the native protein, initially composed of 20.9 percent alpha-helix, 24.5 percent beta-sheet, 19.4 percent beta-turn and 36.8 percent random coil, progressively lost beta-sheet and beta-turn content while gaining alpha-helical and disordered structures. Near-ultraviolet circular dichroism, which probes the microenvironments of aromatic amino acids, revealed that ordered tertiary structure containing tyrosine residues was nearly eliminated during the first 10 to 20 minutes of treatment, although longer treatment partially restored the tyrosine packing signal. Intrinsic fluorescence showed a slight red shift in the tryptophan emission maximum after treatments longer than 20 minutes, indicating that buried tryptophan residues were increasingly exposed to the aqueous solvent.

These structural changes matter because they plausibly explain the loss of immunoreactivity. Conformational epitopes, the folded three-dimensional shapes that B lymphocytes and IgE antibodies primarily recognize, depend on higher-order protein structure, so dismantling that structure destroys the shapes antibodies bind. Increased exposure of aromatic residues may also make the protein more vulnerable to digestive enzymes such as gastric protease, which cleave preferentially at aromatic amino acids, potentially reducing the allergen’s ability to survive the gut intact and sensitize the immune system. The rise in random coil and alpha-helix content coupled with reduced beta-sheet structure has previously been associated with diminished allergenic reactivity in other food proteins.

The authors are careful to flag important caveats. Immunoreactivity here was assessed with rabbit IgG as a surrogate, not with human IgE from peanut-allergic patients, so the findings demonstrate structural epitope destruction but do not directly measure clinical allergenicity; residual IgE binding in sensitized individuals could still trigger reactions. The analyses were also restricted to the soluble fraction, leaving the insoluble precipitate, which may retain allergenic potential, uncharacterized. Only two temperatures were tested, and questions about long-term stability, flavor, texture and nutrient content remain open before industrial application. The team recommends follow-up work with human serum-based assays, basophil activation tests, and in vivo models to confirm clinical relevance.

Even with those caveats, the implications are compelling. HTHP processing is already an established sterilization technique, so a food manufacturer could in principle reduce the immunoreactivity of peanut ingredients using equipment and protocols that exist today, without genetic engineering, enzymatic additives or chemical treatments that raise consumer safety concerns. As a step toward hypoallergenic peanut products, the study offers a detailed structure-activity account of exactly how heat and pressure dismantle one of the world’s most consequential food allergens, molecule by molecule, and a roadmap for the clinical validation that must come next.

Subject of Research: Structural modification and immunoreactivity reduction of the peanut allergen Ara h 1 by high-temperature and high-pressure processing

Article Title: Structural modifications and immunoreactivity reduction of peanut allergen Ara h 1 under high-temperature and high-pressure processing

Article References: Wang, Y.-Q., Li, Y.-C., Duan, H.-Y., Zhu, H.-K., Jiang, L., & Qian, H. (2026). Structural modifications and immunoreactivity reduction of peanut allergen Ara h 1 under high-temperature and high-pressure processing. Discover Chemistry, 3(1), Article 542. https://doi.org/10.1007/s44371-026-01004-w

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01004-w

Keywords: peanut allergy, Ara h 1, food allergen, high-pressure processing, immunoreactivity, protein structure, circular dichroism, atomic force microscopy, ELISA, food processing, allergenicity, food safety