Browsing by Author "Rahikainen, Antti"

The aim of the literature review was to research barley proteins, metal-catalyzed oxidation and subjects related to it, like antioxidants and oxidation reactions in beer. In addition ACE inhibition was looked into. The object of the experimental part was to find out if the proteins of a barley-based industrial side product can be modified by metal-catalyzed oxidation or enzymatic hydrolysis, and how these treatments affect the different proteins in the sample material. In addition, the possible ACE inhibition activity of the reaction products was determined. The sample material was a protein-rich side-product of barley starch production. Two protein fractions were extracted from the material; an alcohol soluble fraction and a reduced fraction. The modification of the proteins in the sample fractions by oxidation and hydrolysis was determined with gel electrophoresis and size exclusion chromatography. The ACE inhibitory activity of the small peptides from these reactions was determined with UV-VIS spectroscopy. Three protein groups were identified from the sample material; polymeric B hordein, monomeric B hordein and C hordein. Contrary to expectations metal-catalyzed oxidation did not break down any of the proteins in the sample; instead it aggregated the proteins into bigger units. The enzyme treatment hydrolyzed the proteins effectively. Small peptides from the enzyme hydrolysis had an ACE inhibition IC50 of 246 µg/ml, which is similar to gluten hydrolysates IC50 of 29 µg/ml. IC50 is the inhibitor concentration where 50% of enzyme activity is inhibited. Instead of breaking down the subject proteins metal-catalyzed oxidation aggregated them, and thus it could not be used to make ACE inhibitory peptides. Enzyme hydrolysis was found to be a valid method of inhibitor peptide production. The peptides produced had an ACE inhibition capacity similar to previously known ACE inhibitory food hydrolysates.