Volatolomics study of X-ray irradiated dairy products by HSSPME/GC-MS

The increasing demand for raw and fresh dairy products, such as soft cheese, with desired organoleptic characteristics and health benefits, requires alternative technologies for inactivation of pathogenic microorganisms in particular of Listeria monocytogenes [1, 2]. In a report of the European Commission [3] and in a recent review [4], the use of food irradiation in half a century of studies is well summarized highlighting the potential benefits of this preservation technique. In Europe, the general application of X-rays to dairy products has been limited to one cheese (Camembert) [5-7], but the irradiation processing of raw and fresh dairy products is of great interest to the food industry. However, irradiation treatments may cause possible biochemical changes in lipid and protein profiles that can affect the quality and safety of products [1]. For these reasons, the purpose of this work was to study the volatile organic compounds (VOC) in Xray irradiated soft cheeses. A volatolomics approach based on headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was developed to evaluate the irradiation effects on the volatile profile of soft cheeses, as a function of different radiation treatment parameters. Five different SPME fibres, namely polyacrylate (PA), polydimethylsiloxane (PDMS) carboxen/polydimethylsiloxane (CAR/PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB) and divinylbenzene /carboxen/polydimethylsiloxane (DVB/CAR/PDMS), were tested in terms of number and relative amount of compounds extracted. Moreover, temperature and extraction time were evaluated for the HS-SPME process efficiency. The volatile compounds of 0, 1.5 and 3 kGy irradiated samples were extracted by the selected SPME fibre and analyzed by the optimized method. VOCs, identified by means the linear retention index and by MS data obtained from NIST library, were analyzed by a multivariate statistical approach in order to investigate the generation of off-odors and flavors induced by X-ray irradiation and to understand the quality and maintenance of the nutritional and sensorial values. Volatile compounds belonging to chemical classes of acids, alcohols, aldehydes, esters, and miscellaneous were identified in all the experimental samples and interesting variations were noted among them as a function of the irradiation dose.