Determinants for yield and quality of zein extracted from corn gluten meal

摘要

An investigation of twelve commercial corn gluten meal (CGM) samples revealed that zein extraction yield was affected by CGM quality, especially the red color intensity and the [alpha]-zein content of CGM, with correlation coefficients of -0.57 and +0.55, respectively (p \u3c 0.1). Zein extracted from CGM with lower red color and higher [alpha]-zein content had higher yield, protein recovery and purity. The protein recovery increased as purity increased (r = 0.76, p \u3c 0.01);Two maize hybrids with different protein content were used to produce CGM in a pilot-plant wet-milling facility. The maize with the higher protein content produced gluten with the higher yield and protein content. Five different drying treatments of CGM showed that freeze and spray drying produced a relatively lighter colored gluten meal compared to high temperature oven-dried CGM. Color differences in CGM were the result of both drying temperature and maize hybrid;Zein extraction yield, protein recovery and protein purity were significantly higher in the CGM obtained from high protein content maize than from low protein content maize. The yield and protein recovery decreased as oven temperature increased. This result may be due to the cysteine residues of zein reforming disulfide bonds during heating and decreasing protein extractability. Zein extraction yield, protein recovery, and protein purity were also significantly lower in the freeze- and spray-dried CGMs compared to oven dried CGMs. Smaller deamidation during drying and hydrophobic interaction among zeins may be the major factors that result in these lower yields;Small amounts of phosphate (0.001-0.005M) added into the extraction solvent notably increased zein extraction yield (38-50%) for the CGMs with both high and low slurry pH. The [alpha]-zein distribution, estimated by high performance liquid chromatogram and isoelectric focusing, showed no effect of phosphate.