Suprasolv grade

Volatile organic chemicals (VOCs) from all the dog hair samples were entrained as described previously [61 (link)]. Briefly, charcoal-filtered air (15ml sec^-1) was passed through the inlet port of a quick-fit Dreschel head into a 50ml round-bottom quick-fit glass flask which contained the dog hair (1g). The air from the effluent port of the Dreschel head passed into a Orbo-402 Tenax-TA trap (8.75cm) (Sigma-Aldrich Company Ltd, Dorset, UK) via a 10cm length of Teflon tubing. Hair samples were entrained for 2.5h and the collected VOCs were recovered by elution of the Orbo tube with n-hexane (SupraSolv grade; Merck, Germany) (2ml). A fresh Orbo tube was used for each entrainment dog hair sample. Each eluted sample was concentrated to a final volume (ca. 500μl) under nitrogen and then sealed in a clean glass Pasteur pipette and stored (-20°C) until further analysis.

To enable accurate chemical compound extractions, powders of the cheese samples were prepared. Therefore, cheese core and rind samples were frozen using liquid nitrogen (Air Liquide, Paris, France) and subsequently milled into a fine powder with a coffee grinder (De’Longhi KG49, Treviso, Italy). These cheese powders were subjected to two types of extractions. To assess organic acids, free amino acids, and biogenic amines, an aqueous extraction was performed, as described previously (Le Boucher et al., 2016 (link); Zhang et al., 2019 (link)). Briefly, 1.0 g of cheese powder was mixed with 9.0 mL of ultrapure water (Milli-Q; Merck) on a rotating wheel at 30 rpm for 30 min at room temperature, followed by centrifugation at 1,000 × g for 5 min. Extracts were stored at −25°C until further analysis. To assess volatile organic compounds, ethyl acetate extracts were prepared by mixing 0.5 g of cheese powder with 9.5 mL of ethyl acetate (SupraSolv^® grade; Merck) and supplemented with 100 μg/L of toluene-D8 (Sigma-Aldrich) as internal standard (IS). Ethyl acetate extracts were filtered with a Millex Syringe Driven Filter Unit (Millex; Merck) and immediately used for further analysis.