ARS | Publication request: Removing peanut allergens by tannic acid

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2011
Publication Date: March 14, 2012
Citation: Chung, S., Reed, S.S. 2012. Removing peanut allergens by tannic acid. Food Chemistry. 134:1468-1473.

Interpretive Summary: Tannic acid (or tannin) (TA) is an antioxidant commonly found in coffee and tea. When at high concentrations, TA binds and forms insoluble pellets with proteins, including peanut allergens; however, the reaction could be reversible (i.e., the pellet dissociates and releases the allergens) if the pellets are not stable under acidic and alkaline conditions (e.g., in stomach and intestine). Allergens in a stable pellet presumably would pass through the digestive system without being absorbed or causing an allergic reaction. Our objectives were to determine the efficacy of TA in forming insoluble pellets with peanut allergens, and examine if the pellets release the allergens under acidic and alkaline conditions (pH 2 and pH 8). TA of different concentrations (0.25-2 mg/mL) was added to a peanut butter extract (5 mg/mL), neutral pH 7.2, stirred and filtered. Filtrates (I) and insoluble pellets were obtained. The latter were further suspended in solution, pH 2, stirred, filtered, and re-suspended in another solution, pH 8, stirred and again filtered. Filtrates from these two steps (II & III) were analyzed for allergen release, compared to filtrates (I). Allergenic potency of filtrates (I) was determined, using a pooled plasma from individuals with peanut allergy. Results showed that peanut allergens were removed from the extract to a different extent, depending on the TA concentration. Pellets formed at TA > 0.5 mg/mL were stable at pH 2 and 8. Allergenic potency of the TA-treated extracts was reduced accordingly. We concluded that pellets formed from treatment of a peanut butter extract (5 mg/mL) with TA at 0.5-2 mg/mL were stable at pH 2 and 8, and that the allergenic potency of the extracts were reduced by 75-100% with TA at 1-2 mg/mL. The implication of the finding is that TA may be useful for the preparation of low-allergen peanut products/beverages, or the removal of peanut allergens due to accidental ingestion of peanut residues hidden in foods.

Technical Abstract: Tannic acid (TA) is known to bind and form insoluble complexes with proteins, including peanut allergens; however, whether such complexes would dissociate and release the allergens at pH 2 and 8 (i.e., gastric and intestinal pH) is not clear. Release of the allergens in the gut could lead to absorption, and consequently an allergic reaction. The aims here were to remove major peanut allergens as insoluble TA complexes, and to determine if the complexes would dissociate or release the allergens at the pH indicated. TA at various concentrations (0.25, 0.5, 1, and 2 mg/mL) was added to a peanut butter extract (5 mg/mL; pH 7.2), stirred, and centrifuged. The precipitates were then suspended in buffer at pH 2, centrifuged, re-suspended at pH 8, and centrifuged. Supernatants from each step were analyzed by SDS-PAGE and ELISA. For comparison, gallic acid (a phenolic monomer) was examined in the same way. The effect of NaCl (1 M) on complexes was also determined. Results showed that complexes formed at a TA concentration > 0.5 mg/mL did not release major peanut allergens at pH 2 and pH 8; nor did they release the allergens in the presence of 1 M NaCl. By contrast, complexes formed from gallic acid released the allergens at the pH indicated. IgE binding or the allergenic potency of the extracts was reduced substantially, especially at a higher TA concentration (1-2 mg/mL) after treatment. The finding implies that TA may be useful for the preparation of low-allergen peanut products/beverages, or the removal of peanut allergens due to accidental ingestion of peanut residues hidden in foods.