Effect of microwave and infrared drying over polyphenol content in Vaccinium meridionale (Swartz) dry leaves

Abstract

In the present work the drying of blueberry (mortiño) leaves (Vaccinium meridionale-Swartz) was done using a hybrid equipment with infrared drying and normal microwave drying. During the drying tests there was a record of moisture content versus time; samples of leaves were taken during the drying time to analyze total phenol (PT) content, FRAP assay and catechin measures by HPLC-DAD. The PT analysis shows that its content in dry blueberries, increased 12 times more with the microwave drying than infrarred drying. While FRAP assay shows that dry blueberries antioxidant capacity increased nine times more with microwave process in comparison to infrared process. In the catechins content by HPLC-DAD in dry blueberries, a better result for concentration was found in microwave process than in infrared process. Similar result occurred for (−) epicatechin. Finally, (+) catechin concentrations in blueberry leaves were compared with commercial materials such as tea leaves and mate leaves. Practical applications: The consumption of nutraceutical products rich in polyphenols has become important in the last decades. In this research, the effect of microwave and infrared drying on the content of polyphenols on blueberry leaves (Vaccinium meridionale, Swartz) was studied because it was found in previous studies that the leaves contain a potential of polyphenols that can be used to develop nutraceutical beverages similar to tea drinks.