Comparison of aroma active compounds in fresh Thai holy basil leaves from 2 varieties

Abstract

Holy Basil is an herb with a high consumption in Thailand domestically and internationally due to its unique odor. A study on the aroma active profile of holy basil would allow for better quality control and food product development. The goal of this study is to identify and compare aroma active compounds in fresh Thai holy basil leaves from 2 varieties (Ocimum tenuiflorum var. Rama and Ocimum tenuiflorum var. Shyama) using sensomics approach. First, olfactory profiling was performed by trained panelists to characterize odor attributes and their intensity. Second, volatile compounds were isolated by solvent extraction, and non-volatile constituents were removed by solvent-assisted flavor evaporation and concentrated using the Vigreux column and microdistillation. Third, extract was injected into the gas chromatography-olfactometry with flame ionization detection (GC-O/FID) to screen for odor quality associated with the retention index (RI). Potential aroma active compounds were determined through aroma extract dilution analysis (AEDA). Gas chromatography-mass spectrometry (GC-MS) enables compound identification by comparing mass spectra with RI and odor quality from GC-O/FID. From olfactory profiling, red holy basil leaves had stronger overall attributes than white holy basil leaves. Red holy basil leaves have stronger minty, green, pungent, and fatty/waxy attributes than white holy basil leaves but have lower citrus-like attribute. Among the potential aroma active compounds with high FD factors, white holy basil leaves consisted of only eugenol (FD ≥ 4096), whereas red holy basil leaves consisted of both eugenol (FD 2048) and methyl eugenol (FD ≥ 4096). In white holy basil leaves, the unique flowery odor might be contributed from 2-hexanol (FD 512) and α-farnesene (FD 1024). Moreover, the distinct eucalyptus-like odor might potentially come from cis-sabinene hydrate (cis-4-thujanol) (FD 2048). In red holy basil leaves, herbal odor was potentially come from 3 high FD factor compounds, including 1-decen-3-ol (FD 1024), naphthalene (FD 2048), and 1-undecen-3-ol (FD 2048), while only 2 compounds with lower FD factor, including trans-4,5-epoxy-(E)-2-heptenal (FD 512) and caryophyllene oxide (FD 1024), were presented in white holy basil leaves.