Browsing by Subject "peroksigenaasiaktiivisuus"

Oat (Avena sativa) contains peroxygenase enzyme (POX), which has been suggested to be partly responsible for the formation of the bitter taste in aged oat products. Knowledge concerning heat stability and working range (pH and temperature) of oat POX is currently limited. The aim of the study was to investigate oat ́s POX activity and factors contributing to it. To find out variability of activity, laboratory scale de-hulled, non-heated oat groat samples were analyzed for POX activity. Activities of non-heated groats and oat flour from the milling process with heating were compared to see how well the aforementioned processes inactivated POX enzyme. Inactivation by heat treatment was also carried out in a laboratory scale kilning study. Variables were groat moisture, heating temperature and heating time. Furthermore, effects of pH, temperature and addition of calsium in POX activity were studied. First peroxygenase was extracted from the milled oat. Then the oat extract, substrate (methyloleate) and oxidant (cumene hydroperoxide) were allowed to react in predetermined reaction conditions. Finally, fatty acid methyl ester and its epoxide were analysed by gas chromatography combined with flame ionization detector. All the analyzed oat samples were from OatHow project apart from the commercial reference sample. The non-heat treated oat groats were found to vary in their POX activities. Milling process with heating reduced peroxygenase activity compared to non-heat treated groats but did not exhaust it entirely. According to the study the milling process with heating was not able to inactivate POX activity entirely, but was earlier noted to efficiently inactivate peroxidase and lipase. POX activity was reduced with laboratory scale kilning. According to the study, POX is more heat stable than other lipid degrading enzymes in oat. Further research is required to provide more information on oat POX activity, so more stable and high-quality oat products can be able to be produced in the future.