Stability of isoflavones during extrusion processing of corn/soy mixture.
The influence of extrusion processing in the presence of corn on the quantity and quality of genistein, daidzein, and their respective beta-glucoside, acetyl glucoside, and malonyl glucoside derivatives was evaluated. Products of 100% soy (textured) and a blend of 20% soy protein concentrate (SPC) and 80% corn meal (direct-expanded) were extruded, with evaluations before and after extrusion. In addition, a 3 x (3 x 3) split-plot factorial experiment investigated the influence of barrel temperature (110, 130, 150 degrees C), moisture content (22, 24, 26%), and relative residence time (1, 0.8, 0.6) on extruder response and isoflavone profile. The extrusion barrel temperature had the most influence on isoflavone profile, especially decarboxylation of the malonyl beta-glucoside, followed by the moisture content. The amount of extractable isoflavones decreased after extrusion for both the SPC and SPC/corn meal blend when extracted with 80% aqueous methanol but remained approximately the same when first hydrated with water before extraction. However, initially hydrating with water produced enzymatic glycolysis in the unextruded samples, increasing the aglycons dramatically.
Mahungu
S M
SM
Department of Food Science and Human Nutrition, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA.
Diaz-Mercado
S
S
Li
J
J
Schwenk
M
M
Singletary
K
K
Faller
J
J
D005511:Food Handling; D007529:Isoflavones / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry*
D007529:Isoflavones