Reduction of peanut allergenicity by extrusion cooking

Both single-screw and twin-screw extruders were used to study the reduction effects of extrusion cooking on peanut allergenicity. Various extrusion parameters including moisture, pH, barrel temperature, and screw speed, were applied to partly defatted peanut flour or peanut-cornstarch mixtures. Impacts of extrusion on peanut proteins and peanut allergens were evaluated by studying their solubility, SDS-PAGE profile and IgE binding potential.; Radioallergosorbent test inhibition (RAST-I) showed that extrusion with a single-screw extruder at pH 9 drastically reduced allergenic potential of phosphate buffered saline (PBS) soluble proteins by 99%, while extrusion at pH 7 reduced it by 36∼94%. Apparent reduction of allergenic potential increased with barrel temperature. Extensive hydrolysis of peanut proteins was observed at pH 9 which may explain the reduction of IgE binding of peanut proteins. At pH 7, extrusion reduced protein solubility in PBS.; Twin-screw extrusion dramatically reduced protein solubility in phosphate buffer. RAST-I showed that extrusion reduced IgE-binding potential of proteins soluble in phosphate buffer by 2∼20 fold. Cornstarch helped to increase the reduction of IgE binding potential as well as the solubility by increasing frictional heat and shear stress. Several intensely IgE binding proteins were found by immunoblotting. Most of IgE binding proteins in unextruded sample were PBS soluble while those in extrudates were 2-mercaptoethanol soluble. Strong IgE binding bands around 18–22 kDa were insolublized by formation of disulfide bonds during extrusion. The 65 kDa subunit (Ara h 1) was insolublized by hydrophobic interaction.; In vitro digestion was conducted to imitate the fate of peanut allergens in the human gastric digestive system. Four strong IgE binding protein subunits with molecular weight of 14, 17, 22 and 65 kDa were found in unextruded peanut flour. No IgE binding was observed by immunoblotting in extrudates at various stages of in vitro digestion. Ara h 1(65 kDa) was found to be susceptible to enzymatic hydrolysis after extrusion. The 14, 17 and 22 kDa subunits in unextruded peanut flour were fairly resistant to in vitro hydrolysis; thus extrusion helped to reduce their IgE binding and made them susceptible to enzymatic hydrolysis.; The relationship between IgE binding capability and allergenicity is not well known. Therefore, an in vivo test should be conducted to evaluate the true allergenicity of the extrudates.