DRYING TREATMENT EFFECTS ON ANTHOCYANINS OF ORGANIC RASPBERRY (CV. HERITAGE) FRUIT

The aim of this study is to compare the effects of some drying processes (hot-air drying and freeze drying) on total anthocyanin content (TAC) for organic raspberry (cv. Heritage) fruits as measured by spectrophotometric method and UPLC technique. The total anthocyanin content was determined in powders obtained from fruits and juice of organic raspberry dried in a hot-air dehydrator at 70 ºC and a freeze dryer at –55 ºC for 45 h. Qualitative analysis revealed the similar anthocyanin profiles in all raspberry powders and showed a clear anthocyanin pattern with the presence of two major compounds. In both fruit and juice of organic raspberry, freeze drying produced a better extraction of the total anthocyanin content either by spectrophotometric method or UPLC and this could be attributed to the thermal degradation and/or oxidation of these compounds during hot-air drying. As matter of fact, the highest total anthocyanin contents were found in milled to juice organic raspberries compared to fresh dried fruits. The results presented in this work indicate that the most appropriate drying method in terms of the anthocyanin content is freeze drying. However, the detailed qualitative analysis of the raspberry powders should help understanding the effects of different drying treatments