Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 4, 1997
Publication Date: N/A
Technical Abstract: Citric acid (CA) was thermochemically reacted with soy protein isolate (SPI), corn distillers' grains (CDG), and corn gluten meal (CGM), to generate products with enhanced metal-binding properties. CA, when heated, forms an anhydride which can interact with a hydroxy or amine functional group of protein. At higher temperatures, this dicarboxyl derivative can form a second anhydride which can crosslink with protein and thereby reduce carboxyl content. SPI, CDG, and CGM, when each was heated in the range 110-120 deg C with CA for 24 hr., yielded reaction products with 3.48, 4.30, and 4.26 mmol COOH per gram of SPI-CA, CDG-CA, and CGM-CA respectively. Based on changes in nitrogen composition when the original protein and CA reaction products are compared, both SPI-CA and CGM-CA were calculated to be 100% dicarboxylic acid derivatives while the CDG-CA derivative was calculated to contain 83.5% dicarboxylic acid and 16.5% monocarboxylic acids. No crosslinking occurred when either SPI or CGM were reacted with CA at temperatures up to 140 deg C. CDG-CA reaction products showed increased crosslinking with heat. FTIR data demonstrated additional absorbances from the CA complexes indicative of ester and carboxyl linkages. The SPI-CA, CDG CA, and CGM-CA complexes effectively bound 1.18, 1.08, and 0.98 mmol Cu**2**+/g, respectively when analyzed by ion plasma spectrometry. Solid state NMR supported the metal-binding characteristics of these CA derivatives.