Quantitative analysis of allergens in peanut varieties and assessment of effects of food processing on peanut allergens
AdvisorChang, Sam K.C.
Peanut, a major allergenic food, has life-threatening potential and is difficult to be totally avoided due to its common use in processed foods. Thermal processing can influence the allergenic properties of peanuts. However, the kinetics of the reactions caused by thermal processing has not been characterized. In our study, kinetics of the commonly used thermal processing methods on a commercial peanut cultivar (Virginia) using five time intervals was conducted. Water-soluble and SDS-sample buffer soluble proteins were extracted sequentially, and analyzed by sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and western-blot using human plasma containing IgE antibodies. The relationships between thermal processing (time) and log transformed water-soluble/total extractable major allergen content could be explained by a simple linear regression kinetic model for most of the processing methods (except high-pressure steaming). Among all the methods with optimal processing point, frying for 6 min had relatively lower IgE binding (linear epitopes) ratio may be due to the fact that this processing condition causing break down, cross-linking and aggregation of Ara h 2, and relatively lower solubility. Besides thermal processing, enzymatic processing also is considered to be an effective method in the allergenicity of peanuts. Eleven peanut lines (Coded MS-1~MS-11, MS-9 is the check and a common cultivar namely Valencia) were pre-screened from 122 peanut lines harvested in 2015 for allergen levels. These pre-screened lines were re-planted in 2016 for further analysis. One line, MS-7, was selected for lower Ara h 1 (8.5-9.5% of total protein) and Ara h 2 (4.2-6.6% of total protein) content in 2015 and 2016. Roasted MS-9 (check) peanut powders were used for enzymatic treatment for enzyme selection. A first order kinetic reaction model was conducted to describe the relationship between enzyme concentration (0-400AzU/g) and IgE-binding property reduction. Among eight food-grade enzymes, bromelain, papain and ficin hydrolysates had lower IgE-binding properties in terms of high IgE-binding property reducing rate (K, ≥ 0.4) and were selected for the following study. MS-7 (selected) & MS-9 (at level of 200AzU/g) hydrolyzed by three selected enzymes (200AzU/g) were used for IgE binding property comparison, TGase crosslinking and functional properties study. After hydrolyzed by the selected enzymes (200 AzU/g), the emulsion and foaming stabilities were decreased. Emulsion and foaming stabilities were increased in TGase (5U/g protein) crosslinked hydrolysates, which were even higher than soy protein isolate (SPI). The IgE-binding properties of TGase treated hydrolysates were similar to the hydrolysates without TGase treatment. MS-7 hydrolysates (with/without TGase) possessed less IgE-binding properties and similar functionality as compared with MS-9 hydrolysates.