Characterisation of aroma-active compounds in dried Dendrobium spp. stems (Shihu) using GC-Olfactometry and a modified NIF-SNIF method

Dendrobium orchid stems (Chinese name Shihu) are becoming popular ingredients in food and drinks such as wine, teas and desserts, however, its aroma chemistry is not currently understood. Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Olfactometry (GC-O) were used to analyse two Dendrobium species. The Nasal Impact Frequency-Surface of Nasal Impact Frequency (NIF-SNIF) method was employed on thirteen untrained panellists using a newly built open-source software ("nif-simple"). An expert annotated odour descriptions and intensities of NIF-SNIF peaks. Twenty-four volatile aroma compounds were found using GC-MS, with 22 shared compounds and 17 reported for the first time. GC-O NIF-SNIF indicated nine aroma compounds were aroma-active in D. nobile and D. officinale. Five were found in both species suggesting that they are species-independent markers. Aroma-active compounds were characterised as brown, mushroom, metallic, nutty and potato aromas. Methional (NIF 83 %) and 1-octen-3-one (NIF 81 %) were most frequently detected in D. nobile and D. officinale respectively, and this study proposed aroma formation mechanisms in dried Dendrobium stems. Modified Frequencies demonstrated that NIF-SNIF is an effective GC-O method for identifying key aroma-active compounds. Understanding the flavour properties of Shihu could enhance its global appeal and encourage NIF-SNIF to be used in future studies.