Effect of different tea manufacturing methods on the antioxidant activity, functional components, and aroma compounds of Ocimum gratissimum

Ocimum gratissimum is a herbaceous medicinal plant known for its high antioxidant activity. In the present study, we investigated the effect of different tea manufacturing processes in retaining the biochemical properties of O. gratissimum and determined which of the processes yields a high-quality tea. We determined the color tone, total polyphenol content (TPC), odor, 2-diphenyl-1-picrylhydrazyl (DPPH) values, and hydrophilic oxygen radical absorbance capacity (H-ORAC) of treated samples. Steaming time affected the color tone, TPC, DPPH value, chicoric acid content, and odor, while the drying temperature and fermentation treatment affected all the parameters. Furthermore, caryophyllene, germacrene-D, and eugenol were identified as the main aroma compounds in O. gratissimum. Our findings indicate that the drying temperature and fermentation treatment are the major factors affecting the biochemical properties and acceptance quality of O. gratissimum tea. Among the different treatments used, machine-drying without steaming treatment was the best on odor. Freeze-drying, which is more costly, was the best on the TPC and antioxidant activities; however, it was found that MD, which is relatively cheap compared to freeze-drying treatment, maintained high TPC, DPPH, H-ORAC values, and chicoric acid content by steaming for 2 min before drying.