Phenolic Content of Apple Pomace Affected by Their Microwave Irradiation

Thermal degradation mechanisms and products of some polyphenols, such as quercetin and rutin, have been intensively observed. The structural changes of polyphenols caused by food processing, may lead to different changes. The aim of this work was to test the changes of TPC, selected individual phenols and antioxidant activity of apple pomace gained from producers and compared to the samples prepared in laboratory conditions caused by microwave irradiation. Antioxidant activity was determined by the DPPH method, total polyphenolic content with use of Folin-Ciocalteau reagent and individual phenolic substances by HLPC -DAD method. The control samples were treated by the microwave radiation for 1 min. in a microwave oven at 650 W. The results of DPPH method showed an increased inhibition of DPPH radical, so higher antioxidant activity, mainly at laboratory prepared samples of pomace was detected. At TPC evaluation, an increase in the content of total polyphenols was observed similarly, at 3 of 4 irradiated samples the significant increase was detected at the level of significance p=0.001. Several individual phenols were detected after irradiation of pomace in higher amounts as well. Application of microwave irradiation in the extraction process might lead to significant increase of the total phenolic content.