Leland C. Dickey

Angiotensin I converting enzyme-inhibitory peptides from commercial wet- and dry-milled corn germ.

Bioprocesses were developed to enhance the value of proteins from deoiled corn germ. Proteins were hydrolyzed with trypsin, thermolysin, GC 106, or Flavourzyme to generate the bioactive peptide sequences. At an enzyme to substrate ratio of 1:100, protein hydrolysis of wet-milled germ was greatest using thermolysin followed by trypsin, GC 106, and Flavourzyme. For the dry-milled corn germ, protein hydrolysis was greatest for GC 106 and least for Flavourzyme. Electrophoretic patterns indicated that the hydrolysis conditions used were adequate for generating low molecular weight peptides for both germs. Unhydrolyzed dry- and wet-milled corn germ did not appear to contain angiotensin I converting enzyme (ACE)-inhibitory peptides. After hydrolysis with trypsin, thermolysin, and GC 106 but not Flavourzyme, ACE inhibition was observed. ACE inhibition was greatest for the GC 106 hydrolysate for both wet- and dry-milled corn germ. Denaturing the protein with urea before hydrolysis, in general, increased the amount of ACE-inhibitory peptides found in the hydrolysate. Membrane fractionations of both the wet- and dry-milled hydrolysates indicated that most of the ACE-inhibitory peptides were in the <1 kDa fraction. Examination of the control total protein extracts (before treatment with proteases) from wet- and dry-milled germ revealed that neither had ACE-inhibitory properties. However, when both total corn germ control protein extracts were fractionated, the <1 kDa fraction of wet-milled corn germ proteins exhibited ACE inhibition, whereas the comparable low molecular weight fraction from dry-milled corn germ did not.

Quantitative Analysis of Corn Zeins by Capillary Electrophoresis

ABSTRACT Kjeldahl analysis is commonly used to measure zein proteins in corn maize (N × 5.7) with no attempt to eliminate contribution from other nitrogen sources. In this study, dry milled corn was extracted with 70% ethanol or 0.1N NaOH and the zein content of the extract measured using capillary electrophoresis in the presence of sodium dodecyl sulfate. The amount of zein protein in alcohol extracts, using this method, was in good agreement with that determined by Kjeldahl nitrogen analysis. However, less than half of the Kjeldahl nitrogen in the alkaline extracts could be attributed to corn zein. Reproducibility expressed as relative standard deviation for migration time and peak area was 0.10 and 1.05, respectively. The technique permits rapid analysis of a large number of samples without interference from other compounds present in the extracts.