## 1 Introduction
The combination of using human sensory and instrumental analytical approaches delivers comprehensive datasets that allow correlations to be drawn between specific aroma notes and the respective compounds eliciting these. Reports in the scientific literature on the aroma of gin and the related constituent aroma compounds are limited. A comparative sensory evaluation study of six different gins that focused on the attributes _juniper_, _citric_, _aniseed_, _licorice_, and _spice_ reported marked differences between London dry gins and gins with different geographical typicality [8]. A study investigating the influence of distillation parameters by comparing six different gins revealed that the use of a greater amount of botanicals during distillation led to higher intensity ratings of sensory descriptors [9]. In terms of their volatile chemical constituents, several studies utilized GC-MS to examine the predominant compounds, whereby monoterpenes were the most frequently identified compounds, assigned mainly to juniper and coriander oil [9; 10; 11; 12; 13]. Semi-quantitative analysis of the volatile fractions of distilled gins identified 70 volatile substances, also predominantly monoterpenes, as well as sesquiterpenes, and their oxygenated derivatives [14]. While the aforementioned studies undertook comprehensive analyses of VOCs in gin, they did not differentiate between odorless and aroma-active volatiles. Only one study to date has reported on the latter, using GC-O analysis in combination with the detection frequency method [15], while others discussed the concentrations of some volatiles in relation to their odor thresholds (OTs), determined in aqueous or 20%vol. ethanolic solutions [9; 10]. Of the odor-active substances detected, 38 were subsequently identified using GC-MS and were found to be primarily mono- and sesquiterpenoids. As outlined above, GC-O or GC-MS/O analysis with AEDA is a useful method to explore relative contributions of individual compounds to the overall aroma of a sample. This approach can be combined with stable isotope dilution analysis (SIDA) to quantify the concentrations of selected (odor-active) volatiles in a sample, as has been previously applied to other alcoholic spirits, such as Bourbon whiskey and rum [16; 17; 18; 19; 20; 21]. Alternatively, the concentrations of aroma-active constituents can be determined by the addition of internal standards, as has been carried out for rum, cognac and the Chinese liquor Daqu, amongst others [22; 23; 24]. For additional insight into the relevance of individual odorants to the overall aroma, odor activity values (OAVs) can be determined, which are defined as the ratio of the concentration of an odorant in a sample to its odor threshold [16; 17; 18; 19; 20; 21; 24]. In terms of sampling, the extraction of volatiles in gin may be performed via liquid-liquid extraction [10; 15], which was found to be most suitable for GC-O analysis using dichloromethane [15]. For GC-MS analysis of gin volatiles, headspace solid-phase micro-extraction (HS-SPME) [8; 9; 13; 14] or stir-bar sorptive extraction (SBSE) [12] have been applied. A study comparing the application of headspace sorptive extraction (HSSE), SBSE and SPME (albeit of volatiles from Arabica coffee), observed higher recoveries using HSSE or SBSE than via SPME due to the high amount of sorbent applied [25]. Reports on quantitative studies of key aroma compounds in gin in the scientific literature are lacking. Consequently, the aim of the present work was to identify the key aroma compounds in two locally distilled gins produced using different numbers of botanicals. GC-O was employed in combination with AEDA to screen for odor-active substances and estimate their relative odor potencies. Further, SBSE sampling with subsequent GC-MS/O analysis using SIDA allowed selected aroma compounds to be quantified in the two gins. Subsequent calculations of the OAVs of these selected compounds provided indications of their relative contributions to the overall aroma of each gin.