Evolution of the volatile compounds along curing in Semimembranosus muscle of the Toscano ham

The volatile profile of Toscano hams from 0 to 18 months of ripening was studied. Ten green hams of 15.60 were seasoned according to the ‘Toscano’ PDO Consortium ripening protocol. Semimembranosus muscle was sampled after trimming (0), 1, 3, 6, 12, 14, 16 and 18 months of ripening by means of 5-mm punch corer. The volatile compound profile was obtained by SPME–GC–MS using an Agilent 7890 Chromatograph equipped with a 5975A MSD with EI ionisation and a three-phase DVB/Carboxen/PDMS 75-μm SPME fibre, exposed in the head space of the vials at 60 °C for 30 min. The identification of volatile compounds (VOCs) was done matching the peak spectra with library database and matching Kovat index (KIS) with KIS from literature. VOCs evolution was studied using a linear model and a multivariate approach, which was performed to test the feasibility of using the VOCs profile to predict the seasoning stage of Toscano ham. Ninety-seven VOCs, belonging to 7 chemical families (29 aldehydes, 16 esters, 14 alcohols, 13 hydrocarbons, 12 ketones, 10 acids, 2 furans and 1 nitrogenous compound), were identified. Firstly, the stepwise discriminant analysis (SDA) was applied to selected 26 compounds able to discriminate low maturing class (LMC) from high maturing class (HMC). Then, canonical discriminant analysis (CDA) was applied using the 26 selected compounds. The two maturing classes resulted clear separated (P <0.0001). Among the 26 compounds the most influencing were: the 2,3-dimethyl pentane, acetophenone and 9-decenoic acid for LMC and dodecanoic, benzeneacetaldehyde, 3-octen-2one and pentanoic acid ethylester for HMC. Dodecanoic acid was the most effective in identifying HMC hams, indeed, it increased from 0 to 18th month. The other high-discriminant compounds followed the same trend during ripening, except for 3-octen-2one, whose lower occurrence in HMC than in LMC, acted as the discriminant factor. Secondly, the SDA was applied only to HMC hams (12, 14, 16 and 18 seasoning months), selecting 17 compounds. Samples seasoned for 14 and 18 months resulted separated (P=0.02). CAN analysis also differentiated “12 months” seasoning class from the other classes and “18 months” class from “16 months” one. The main VOCs associated to the “12 months” class were nonanal, 1,5-Diphenyl-3-methylthio-1,2,4-triazole and 6-methoxy 2-hexanone. Also 3-nonen-5-yne,4-methyl played an important role in the characterization of 18 months samples respect to 14 and 16 ones. The 26 compounds identified in the first scenario could be a useful tool to determine the ripening status of unknown samples. Despite the loss of accuracy observed in the second scenario, also the 17 compounds identified as discriminating within the HMC samples, turned out to be an interesting way to separate at least 12th months samples from 18th ones.