Characterization of volatile compounds in mozzarella cheeses made from bovine and buffalo milk by different aroma extraction and identification methods

High-moisture mozzarella cheese is particularly popular because of its freshness and milky flavor; however, the difference in aroma compound composition between high-moisture mozzarella cheese made from bovine (BOC) and buffalo milk (BUC) remains unclear. Herein, the volatile compounds of 2 kinds of mozzarella cheese were qualitatively and quantitatively analyzed by solid-phase microextraction comprehensive two-dimensional gas chromatography olfactometry time-of-flight mass spectrometry (SPME-GC×GC-O-TOF-MS), solid-phase microextraction-Arrow gas chromatography mass spectrometry (SPME Arrow-GC-MS), and gas chromatography ion-mobility spectrometry (GC-IMS) for the first time. A total of 139 volatile compounds were identified (69 aroma active compounds were sniffed), of which 106 were identified in BOC and 96 in BUC. About 70.5% of these compounds can be identified by GC×GC-O-TOF-MS, exceeding 2.6 times that of GC-IMS. Particularly, 2-methyltetrahydrofuran-3-one (nutty flavor, odor intensity of 3) and methoxy-phenyl-oxime (burnt flavor, 689.47 ± 48.32 μg/kg, odor intensity of 5) were identified as aroma active compounds in BOC for the first time. The sensory evaluation confirmed that 2-methyltetrahydrofuran-3-one is one of the factors responsible for the differences in nutty flavor observed between BOC and BUC. Compared with the 3 aroma extract techniques (SPME, SPME-Arrow and headspace), SPME-Arrow can increase the adsorption capacity of volatile compounds in samples, but required the high separation and high sensitivity detection equipment for more efficient identification of volatile compounds. The combination of the GC×GC-O-TOF-MS, GC-MS, and GC-IMS had obtained a comprehensive aroma profile of mozzarella cheese, which laid a theoretical foundation for the construction of aroma fingerprints of mozzarella cheeses from different milk sources, and provided a basis for the development and application of new dairy products.