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.