Deodorization by Solar Steam Distillation of Rosemary Leaves Prior to Solvent Extraction of Rosmarinic, Carnosic, and Ursolic Acids

This study aims total valorization of rosemary for food applications, moving toward developing an original biorefinery concept using solar steam distillation (SSD) to extract essential oil while preserving active compounds in the raw material, mainly antioxidants, for a further extraction. The deodorization process is important to avoid the extraction of antioxidants with strong aromas which limit their utilization for food preservation. The SSD process was compared with conventional steam distillation (CSD) for essential oil extraction as well as deodorization of dried rosemary leaves. The treated leaves were recovered afterward for the extraction of antioxidants by solvent extraction to recover rosmarinic, carnosic, and ursolic acids. With standard protocol extraction and analysis, the antioxidants seem to be mostly preserved by SSD rather than by CSD. The Folin-Ciocalteu reagent was used to determine the polyphenol content, whereas diphenylpicrylhydrazyl (DPPH) was used to analyze the antiradical properties. It was found that both the polyphenol content and antioxidant activity were preserved after SSD. Scanning electron microscopy (SEM) and fluorescence microscopy showed complete destruction of glandular trichomes for both processes, which indicates that the extraction of essential oil was complete. Overall, the results specify clearly that solar steam distillation (SSD) is a green alternative, an efficient and economical process for essential oil extraction and leaf deodorization.