C: Food Chemistry JFS C: Food Chemistry Effects of Pulsed UV-Light on Peanut Allergens in Extracts and Liquid Peanut Butter S.-Y. CHUNG, W. YANG, AND K. KRISHNAMURTHY ABSTRACT: Pulsed ultraviolet (PUV) light, a nonthermal technology, was used to treat both the peanut extracts and liquid peanut butter. The objective was to determine if such treatment would lead to a reduction in the allergenic properties of the peanut extract and butter. Peanut samples were PUV treated using a Xenon RS-3000C under the following conditions: 3 pulses/s, 14.6 cm from the central axis of the lamp, 4 min (extract) or 3 min (liquid peanut butter). After the treatment, the peanut samples were centrifuged and the supernatants analyzed by SDS-PAGE and competitive inhibition enzyme-linked immunosorbent assay (ciELISA). For comparison, boiling treatments were also performed. SDS-PAGE showed that while boiling treatment had little effect on the peanut allergens, PUV-light- treated samples displayed a reduced solubility or level of peanut allergens (63 kDa). Solubility of another allergen (18 to 20 kDa) was unaffected. Insoluble aggregates formed were responsible for the reduced level of allergens in PUV-light-treated samples. ciELISA showed that untreated samples exhibited an IgE binding 7-fold higher than the PUV-treated samples. It was concluded that PUV light was effective in reducing IgE binding of peanut extracts and liquid peanut butter. The current study provides an approach to the development of a possibly less allergenic peanut product. However, the reduction in actual allergenicity needs to be confirmed by clinical studies. Keywords: IgE antibodies, peanut allergens, peanut butter, pulsed UV light Introduction P ulsed ultraviolet (PUV) light is a nonthermal, high-peak power technology that consists of intense flashes of broad-spectrum white light with wavelengths from 200 nm in the ultraviolet (UV) to 1000 nm in the near-infrared region (Rowan and others 1999). Each pulse may have up to 90000 times the intensity of sunlight at sea level, and may last only a few hundred millionths of a second, and thus a PUV light system can produce very high peak power pulsed light in a very short time. Because of its high peak power, PUV light has been successfully used as a sterilization tool to kill bacteria and fungi in foods and fruits (Krishnamurthy and others 2004, 2007; Lagunas-Solar and others 2006; Bialka and others 2008). The killing effect is 4 to 6 times higher than that of the conven- tional continuous UV light at the same energy level (Dunn and oth- ers 1995; MacGregor and others 1998). The advantage of using PUV light is that PUV light can enhance the shelf life and quality of foods without causing sensory changes (Dunn and others 1995; G´ omez- L´ opez and others 2005; Lagunas-Solar and others 2006). While PUV light is generally aimed at killing foodborne organ- isms, little has been done or is known about its effect on proteins that cause peanut allergy. To date, at least 8 peanut allergens have been identified, of which two, namely, Ara h 1 (63 kDa) and Ara h 2 (18 to 20 kDa) are considered to be the major peanut allergens, because Ara h 1 and Ara h 2 are recognized by 70% to 90% of sen- sitized individuals (Burks and others 1998). These allergens are re- ported to react with carbohydrates to form advanced glycation end products (AGE) during heating or roasting of the peanuts, and as MS 20070938 Submitted 12/17/2007, Accepted 3/26/2008. Author Chung is with U.S. Dept. of Agriculture, Agricultural Research Service, South- ern Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, U.S.A. Authors Yang and Krishnamurthy are with Dept. of Food & Animal Science., P.O. Box 1628, Alabama A&M Univ., Normal, AL 35762, U.S.A. Direct inquiries to author Chung (E-mail: siyin.chung@ ars.usda.gov). a result, the allergenic properties of the peanuts increase (Chung and Champagne 1999, 2001; Maleki and others 2000). To reduce the allergenic properties of peanut allergens, several approaches such as treatments with peroxidase, polypheol oxidase/caffeic acid, copper/hydrogen peroxide, and phytic acid have been developed in our laboratory (Chung and others 2004, 2005, 2006; Chung and Champagne 2007). In this study, we investigated the feasibility of using PUV light to lower the allergenic properties of peanut extracts and liquid peanut butter. The rationale was that as in other high peak power technolo- gies such as pulsed electric field and matrix-assisted laser pulsed evaporation (Castro and others 2001; Jelinek and others 2007; Wei and others 2007), PUV light may cause protein insolubility, and thus may lead to a reduction in the levels of peanut allergens in the extracts and liquid peanut butter. Therefore, the objective of this study was to treat the peanut extracts and liquid peanut but- ter with PUV light and determine if the immunoglobulin E (IgE) binding was reduced after treatment. For comparison, boiling treat- ment was also performed. In this study, whole peanut seeds were not used and treated because PUV light is incapable of penetrating the seed coat to reach and affect the inner peanut proteins. Materials and Methods Materials Tris buffer saline (TBS), 96-well microtiter plates, ¯ o- phenylenediamine, and Tween 20 were purchased from Sigma Co. (St. Louis, Mo., U.S.A.). Tris-glycine precast gels (4% to 20%), gel electrophoresis apparatus, reagents for sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), and goat antihuman immunoglobulin E (IgE)-peroxidase were purchased from Invitrogen (Carlsbad, Calif., U.S.A.). Superblock blocking buffer, GelCode Blue Stain Reagent, and bicinchoninic acid (BCA)-protein assay kit were purchased from Pierce Chemical Co. (Rockford, Ill., U.S.A.). Human plasmas from 3 individuals No claim to original US government works C400 JOURNAL OF FOOD SCIENCE—Vol. 73, Nr. 5, 2008 Journal compilation C  2008 Institute of Food Technologists doi: 10.1111/j.1750-3841.2008.00784.x Further reproduction without permission is prohibited