Isolation of terpenes and aroma compounds in mountain herbs and typical Italian goat cheese by SBSE and TD-GC-MSD

Breeding of dairy goats in Italy represents a marginal rural activity. Italian goats are reared in areas where no other farming activities could be performed, therefore these animals represent an alternative in overworking the poorest mountain Alps pastures. Mountain cheeses are still being produced today in much the same way as in the past and they are made only during summer period when goats are reared on alpine pastures. The production of their milk is quite limited, for this reason these cheeses are highly valued dairy products. A new sampling technique, Stir Bar Sorptive Extraction (SBSE), was applied in this work for analysis of terpenes and aroma compounds in several pasture essences (i.e.: Rumex acetosella; Betula alba; Rosa canina; Corylus avellana) and then in typical artisanal goat cheese produced in mountain pasture, in order to determine the occurrence of terpenes in natural grassland of Alps and the transfer to dairy products. A small stir bar, (10 mm length) coated with polydimethylsiloxane, (0.5 mm PDMS film thickness) was placed in the cheese samples diluted with LC-grade water and in the headspace of mountain herbs and stirred for about 1 hours. After extraction PDMS stir bar was thermally desorbed at 200 °C for 5 min and the aroma compounds were cold trapped in the PTV inlet at –150 °C. The isolated compounds were then analysed using gas chromatography-mass spectrometry (GC-MS). Several terpenes were isolated from pasture essences and cheese samples such as cymene, caryophyllene, γ-terpinene, α-pinene, γ-germacrene, thymol and δ-carene. Aldehydes and ketones predominate in cheese samples, followed by free fatty acids and esters. Some terpenes isolated from mountain herbs, in particular from dicotyledons mix of highland pastures, were detected also in cheese samples and could be used to link them to the sites of production.