The effect of cryomill and ultrasound on antioxidant activity of rapeseed press cake

Cilj ovog istraživanja bio je ispitati utjecaj novih tehnologija, odnosno kriogenog mljevenja i ultrazvuka visokog intenziteta na udjel fenolnih spojeva i antioksidacijsku aktivnost pogače uljane repice. Nakon proizvodnje ulja, dobivena pogača usitnjena je na kriomlinu uz hlađenje pomoću tekućeg dušika kroz 12 minuta, a zatim tretirana ultrazvukom visokog intenziteta pri amplitudama od 60 %, 80 % i 100 % i vremenu od 3, 6 i 9 minuta. Samljevenoj pogači određen je sastav masnih kiselina, slobodni i vezani polifenolni spojevi te antioksidacijska aktivnost. Tretmani kriomljevenja i ultrazvuka pokazali su statistički značajan utjecaj na udio miristinske, palmitoleinske, heptadecenske, heptadekanske i eruka masne kiseline (p ≤ 0,05). Vrijeme tretmana ultrazvukom značajno je utjecalo na koncentraciju p-kumarinske kiseline slobodnih polifenola (p ≤ 0,05) dok je amplituda imala utjecaj na udio ružmarinske kiseline kod vezanih fenola (p ≤ 0,05). Koncentracija sinapinske i p-kumarinske kiseline statistički značajno korelira s antioksidacijskom aktivnosti slobodnih polifenola, dok kod vezanih polifenola statistički značajnu korelaciju pokazuje koncentracija ferulinske i p-kumarinske kiseline (r > 0,666).The aim of this study was to determine impact of cryogenic grinding and high intensity ultrasound on the release of phenolic compounds and antioxidant activity of rapeseed cake. After the oil production, the rapeseed cake was grounded on cryomill with liquid nitrogen cooling for 12 minutes and then treated with high intensity ultrasound at amplitude of 60 %, 80 % and 100 % while the extraction time was 3, 6 and 9 minutes. Free and bounded phenolic compounds, fatty acid composition and antioxidant activity of milled cake were determined. Cryogenic milling and ultrasound treatments showed statistically significant effect on the content of mirystic, palmitoleic, heptadecenic, heptadecanic and erucic fatty acid (p ≤ 0,05). Time of treatment with ultrasound showed significant impact on p-coumaric acid of free phenols (p ≤ 0,05), while amplitude showed significant impact on rosemaric acid bounded phenols (p ≤ 0,05). Concentration of sinapic and p-coumaric acid had a statistically significant correlation with the antioxidant activity of free phenols while the same was for ferulic and p-coumaric acid for bounded phenols (r > 0,666)