Protein distribution in gluten products isolated during and after wet-milling of maize grains

The protein distribution in five gluten samples isolated during and after w et-milling of maize grains (slurry before and after filtration, total indus trial gluten meal, and coarse and fine fractions obtained after sieving) wa s investigated by sequential extraction. Six fractions (FI-FVI), including residue, were isolated. Heating filtered slurry to draw water away did not alter protein distribution. Compared with values reported in the literature for endosperm protein, we found a decrease in Fl and FIV, respectively, ex tracted with salt alone and with reductant, due to proteolysis and partial elimination of nonprotein nitrogen during slurry filtration, and an increas e in FII and decrease in FIII, alcohol-soluble proteins extracted without a nd with reductant, respectively, due to the presence of SO2 in the steeping liquor. Gluten, with respect to the endosperm from which it originated, wa s richer in zeins (FII + FIII) and glutelins (FV + FVI) due to partial remo val of salt-soluble proteins (FI + FIV) during the isolation process.