## 1 Introduction  
Sheep milk, at around 1.5%, represents a relatively small proportion of global milk production, but its popularity has grown in recent decades [1]. From 1994 to 2013 global sheep milk production grew by 26%, led by dramatic increases in Africa and Asia [1]. As the demand for sheep milk increases and the dairy industry utilizes sheep milk for purposes beyond cheese and other traditional dairy products, it will also need methods to ensure the flavour quality of those products. As noted by [PERSON], [PERSON], and [PERSON], flavour is one of the most important attributes of a dairy product [2]. Excluding work on cheese, a limited amount of literature has directly examined the volatile flavour compounds and the impact of processing on those compounds in sheep milk. [PERSON] et al. investigated the impact of seasonal variation, pasteurization, and spray-drying on the volatile branched chain fatty acids of New Zealand sheep milk [3]. The study found that there were seasonal effects and that spray-drying led to significantly higher levels of those fatty acids [3]. To the best of our knowledge, no studies have investigated the broader range of volatile compounds in spray-dried sheep milk or in New Zealand sheep milk. It is widely acknowledged that there is no perfect volatile extraction technique and when selecting a method, it is important to understand the specific advantages and shortcomings. Previousinvestigations of the volatile attributes of sheep milk have employed both headspace and more traditional distillation and liquid extraction techniques [4; 5; 6; 7; 8; 9; 10]. A benefit of Solid Phase Microextraction (SPME) has been the range of commercially available sorbent phases that can be tailored to selectively recover volatiles of interest. SPME was previously employed to examine the volatiles of sheep milk by [PERSON] et al. as well as [PERSON] at al. [8; 10]. [PERSON] et al. identified 36 volatile compounds using a carboxen/polydimethylsiloxane (CAR/PDMS) fibre in sheep milk [8]. Similarly, [PERSON] et al. identified 37 volatile compounds across eight compound classes, including alcohols, aldehydes, ketones, furans, hydrocarbons, organic acids, terpenes, and sulphur compounds using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre [10]. [PERSON] et al. applied Dynamic Headspace (DHS) to milk from sheep that were fed different diets and identified 22 compounds that included ketones, aldehydes, alcohols, an ester, some hydrocarbons and terpenes [9]. In another series of studies, sheep milk volatiles were evaluated by low pressure distillation and liquid-liquid extraction and 67 volatile compounds in raw ovine milk were identified [4; 5; 6]. The volatiles identified by [PERSON] et al. spanned nine compound classes and included esters, aldehydes, ketones, alcohols, sulphur compounds, lactones, nitrogen compounds, aromatic compounds and a few unknown compounds [4; 5; 6]. It was found by CHARM analysis that esters and aldehydes, along with dimethyl sulphone and indole were potent aroma compounds in raw milk [5]. [PERSON], [PERSON], and [PERSON] postulated the importance of lactones as an aroma-active compound class in the milk but limited recovery of the lactones by their equipment prevented that conclusion to made at the time [5]. The volatile compounds in sheep milk are similar to those found in bovine and other species' milks [5; 11]. The literature addressing bovine milk volatiles is more extensive than for sheep milk and additional isolation techniques have been tested that could prove useful for the evaluation of sheep milk. In a direct comparison of bovine milk volatiles extracted by DHS and SPME, SPME was found to have better reproducibility and similar sensitivity [12]. Indeed, SPME has proved a popular and successful technique for the extraction of milk volatiles and enjoys widespread application to fluid and spray-dried milk samples [12; 13; 14; 15; 16; 17; 18; 19; 20].